fix(renovate): run renovate image directly instead of docker-wrapping action

renovatebot/github-action is a Node wrapper that shells out to
`docker run ghcr.io/renovatebot/renovate`, requiring a Docker CLI + socket
inside the job. The Gitea runner executes the job in a plain node:22 container
with neither, so it died on "Unable to locate executable file: docker".

Run the renovate image as the job container and invoke `renovate` directly —
drops the docker-in-docker requirement. Full tag pinned; Renovate's
github-actions manager keeps container.image bumped.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/renovate.yml

@@ -0,0 +1,42 @@
+name: Renovate
+
+on:
+  # Weekly sweep. Mondays 05:00 UTC — this cron owns the cadence; the repo's
+  # renovate.json5 deliberately has no internal schedule (avoids double-gating).
+  schedule:
+    - cron: '0 5 * * 1'
+  # Manual run for an on-demand sweep from the Actions tab.
+  workflow_dispatch:
+
+# Never let two Renovate runs touch the repo at once.
+concurrency:
+  group: renovate
+  cancel-in-progress: false
+
+jobs:
+  renovate:
+    runs-on: docker
+    # Run the Renovate image *as* the job container and invoke the `renovate`
+    # binary directly. The renovatebot/github-action wrapper is a thin Node
+    # action that shells out to `docker run …` — it needs a Docker CLI + socket
+    # inside the job, which the Gitea runner's plain node container has not, so
+    # it died on "Unable to locate executable file: docker". Running the image
+    # directly drops the docker-in-docker requirement entirely.
+    # Full tag pinned; Renovate's github-actions manager keeps it bumped.
+    container:
+      image: ghcr.io/renovatebot/renovate:43.232.0
+    steps:
+      - name: Run Renovate
+        run: renovate
+        env:
+          # Self-hosted Gitea, not github.com.
+          RENOVATE_PLATFORM: gitea
+          RENOVATE_ENDPOINT: https://gitea.jeanlucmakiola.de/api/v1
+          # Bot-account token (Gitea secret). Needs repo read/write + PR scope.
+          RENOVATE_TOKEN: ${{ secrets.RENOVATE_TOKEN }}
+          # Scope to this repo only — no org-wide autodiscovery.
+          RENOVATE_AUTODISCOVER: 'false'
+          RENOVATE_REPOSITORIES: '["makiolaj/calendula"]'
+          # Commits/PRs authored as the bot, not a real maintainer.
+          RENOVATE_GIT_AUTHOR: 'Renovate Bot <renovate@jeanlucmakiola.de>'
+          LOG_LEVEL: info

.gitea/workflows/translations.yaml

@@ -0,0 +1,41 @@
+name: Translations
+
+# Fast, SDK-free parity check for translation resources, so Weblate PRs (which
+# only touch values-*/strings.xml) get quick feedback without the full Android
+# build. The deeper checks still run in CI via lintDebug (ExtraTranslation).
+on:
+  push:
+    branches:
+      - '**'
+    tags-ignore:
+      - '**'
+    paths:
+      - 'app/src/main/res/values*/strings.xml'
+      - 'app/src/main/res/xml/locales_config.xml'
+      - 'scripts/check_translations.py'
+      - '.gitea/workflows/translations.yaml'
+
+concurrency:
+  group: translations-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check:
+    runs-on: docker
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Ensure python3
+        run: |
+          if ! command -v python3 >/dev/null 2>&1; then
+            if command -v apt-get >/dev/null 2>&1; then
+              apt-get update && apt-get install -y python3
+            elif command -v apk >/dev/null 2>&1; then
+              apk add --no-cache python3
+            fi
+          fi
+          python3 --version
+
+      - name: Check translation parity
+        run: python3 scripts/check_translations.py

.planning/ROADMAP.md

@@ -232,10 +232,26 @@ pass on the existing controls; new toggles ride in with their own features.
 7. ~~Home-screen widget — built on the agenda data source from #6~~ *(done, v2.5.0 — agenda + month widgets)*
 8. App shortcuts: ~~launcher long-press → New event~~ *(done, v2.5.0)*; optional quick-settings tile still open
 
-**Tier 4 — interop & bigger-ticket**
-9. Share event as .ics + receive/open .ics into a prefilled create form
-10. Default reminder applied to new events; then snooze/dismiss notification actions
-11. Drag & drop rescheduling in day/week — big-ticket, own slice (recurring drops reuse the scope dialog)
+**Tier 4 — reliability, data-safety & interop** *(re-ranked 2026-06-17)*
+9. **Reminders — defaults + delivery reliability** *(shipped v2.6.0)* — global
+   default reminder **+ per-calendar override**, bundled with battery-exemption
+   hardening. Full sketch in "Reminders — defaults & delivery reliability" below.
+10. **The `.ics` engine — export + import** *(in progress → v2.7)* — one
+    hand-rolled serializer/parser (zero deps, stays on `kotlinx-datetime`),
+    four surfaces: single-event share + whole-calendar backup (export),
+    open-`.ics`→form + whole-calendar restore (import). Closes the
+    device-local-calendar data-loss gap (#10/#11 merged here). Built as **two
+    sequential branches in one release**: `feat/ics-export` (write side +
+    UID-on-create precursor) then `feat/ics-import` (parser, restore, dedup).
+    Import is liberal-in/strict-out: skip-and-report foreign `VTIMEZONE` /
+    `RECURRENCE-ID` it can't model. Timezone rule: all-day `VALUE=DATE`,
+    non-recurring timed UTC `Z`, recurring timed `TZID`-labelled from the stored
+    `EVENT_TIMEZONE` (no `VTIMEZONE` blocks; resolved against the OS tz DB on
+    import). Plan: `docs/superpowers/plans/2026-06-18-05-ics-export.md`.
+11. **Snooze / dismiss notification actions** *(next, after v2.7)* — follows the
+    `.ics` work; inherits v2.6's deferred exact-alarm/WorkManager decision (snooze
+    must re-fire an alarm).
+12. Drag & drop rescheduling in day/week — big-ticket, own slice (recurring drops reuse the scope dialog)
 
 **Gated — explicit go/no-go before any work (mostly INTERNET-permission calls)**
 - Remote calendar create/edit (re-implements DAVx5; INTERNET + credential storage)
@@ -249,8 +265,9 @@ pass on the existing controls; new toggles ride in with their own features.
 **Unranked / fill-in** — pinch-to-zoom time scale, tablet/foldable layouts,
 full-text search, ICS file import. Pulled in opportunistically, not sequenced.
 
-Debatable calls worth a second look: widget (#7) vs .ics interop (#9) ordering;
-whether drag-drop (#11) jumps ahead given its daily-driver impact.
+Debatable calls worth a second look: whether **local-calendar backup (#10)**
+should lead Tier 4 outright (it's a silent data-loss risk, not a feature);
+whether drag-drop (#12) jumps ahead given its daily-driver impact.
 
 ## Navigation & views
 
@@ -260,9 +277,14 @@ whether drag-drop (#11) jumps ahead given its daily-driver impact.
 - Agenda view (fourth view: upcoming events grouped by day; also the
   natural data source for a future widget)
 - Jump to date — drawer date picker (un-cut from V1)
+- Current-time "now" line in day/week — standard in every calendar, cheap,
+  currently absent. Daily-driver polish.
+- Week numbers in the **month** grid — week view already shows the badge
+  (`WeekNumberBadge`, `WeekScreen.kt`); extend to month for ISO/European users.
 - Pinch-to-zoom time scale in day/week
 - Tablet / foldable layouts *(was v3.0)*
-- Full-text search *(was v3.0)*
+- Full-text search *(was v3.0)* — promote out of "fill-in": for a daily driver
+  with real event history, finding an event is core completeness, not optional.
 
 ## Event editing & creation
 
@@ -297,12 +319,103 @@ whether drag-drop (#11) jumps ahead given its daily-driver impact.
   go/no-go gate as the OSM/INTERNET item below.
 - Move event to another calendar (copy+delete model with a consequences
   warning — deferred from v2.0; `CALENDAR_ID` is sync-adapter-owned) *(was v3.0)*
+- **Local-calendar backup / export** *(Tier 4 #10)* — device-only
+  (`ACCOUNT_TYPE_LOCAL`) calendars are first-class in Calendula but have **no
+  sync and therefore no backup**: a lost/wiped phone destroys them permanently.
+  Whole-calendar `.ics` (VCALENDAR) export to a user-chosen file (SAF), plus
+  restore-on-import that recreates events into a chosen local calendar. Reuses
+  the .ics serializer from the single-event share work; the restore path reuses
+  the import parser. A data-integrity obligation, not a feature.
 
-## Reminders, round two
+## Reminders — defaults & delivery reliability *(implemented 2026-06-17, `feat/default-reminders` — pending on-device review)*
+
+Two themes bundled because both are "make reminders trustworthy" — the core of
+the "Calendula is your only calendar app" promise.
+
+**Built in this slice (A + the safe half of B):** global timed default reminder
++ a **separate all-day default** (day-scale lead times) + per-calendar override
+(timed events), applied on create with manual-edit / calendar-switch / all-day-
+toggle handling; three pickers + per-calendar override list in Settings →
+Notifications; battery-optimisation exemption row (status + system deep-link, no
+extra permission). `resolveDefaultReminder` + prefs round-trips unit-tested.
+Resolution model: all-day events use the all-day global default outright;
+per-calendar overrides govern timed events only. Reviewed (8-angle), fixes
+applied: form-reset state race, label-fn consolidation with the detail screen,
+inline wrapper + single combined flow read.
+
+**Deliberately deferred (documented decisions, not oversights):**
+- *Absolute time-of-day for all-day reminders* — the all-day default is still
+  minutes-before-midnight (day-scale presets), not "9am the day before" (open
+  decision #2's richer half). Per-calendar all-day overrides also deferred.
+- *Self-scheduled alarms* — kept the existing provider-broadcast architecture
+  (open decision #1). The battery exemption is the reliability lever; no
+  `AlarmManager`/`USE_EXACT_ALARM` subsystem was added.
+- *Test-reminder diagnostic* and *battery prompt inside onboarding* — the
+  exemption lives only in Settings for now (onboarding flow untouched to keep
+  the change reviewable).
+
+### A. Default reminders (global + per-calendar override)
+
+**No provider backing.** `CalendarContract` has no column that auto-applies a
+default reminder per calendar — Google's per-calendar defaults live server-side.
+So both the global default *and* the per-calendar override are **app-side
+preferences**, applied by us at event-insert time. We inherit nothing from the
+synced calendar.
+
+- **Storage (DataStore):**
+  - `defaultReminderMinutes: Int?` — global default; `null` = "no reminder".
+  - `defaultAllDayReminderMinutes: Int?` — separate all-day default (all-day
+    reminders are expressed as minutes before midnight / day-before-at-time, not
+    minutes before a start instant — they need their own value).
+  - `perCalendarReminderOverride: Map<Long, Int?>` — keyed by calendar id;
+    **absent key = inherit global**, explicit `null` = "no reminder for this
+    calendar". (Same for an all-day override map if we want per-calendar all-day.)
+- **Apply on create:** a fresh event prefills its reminders list from
+  override-or-global for the preselected calendar. Changing the calendar in the
+  form re-applies the *new* calendar's default **only if the user hasn't manually
+  edited the reminders** — track a dirty flag, mirroring the per-event-color
+  reset pattern (v2.4).
+- **Edit semantics:** defaults apply to **new events only**; never rewrite
+  reminders on existing events on open or on calendar-switch-during-edit.
+- **Settings UI (Notifications sub-page):**
+  - Global default via OptionCard (None / at time of event / 5 / 10 / 15 / 30 min
+    / 1 h / 1 day / custom), plus the separate all-day default.
+  - Per-calendar overrides: a row per writable calendar (in the Calendars screen
+    or a Notifications subsection), each opening the same OptionCard with a
+    leading **"Use global default"** option.
+
+### B. Delivery reliability (exact alarms + battery)
+
+The provider broadcasts `EVENT_REMINDER`, but on modern Android (Doze / OEM
+battery managers) delivery can be silently delayed or dropped. v1.4 deferred this;
+it directly undermines the feature's premise, so it rides in here.
+
+- **Exact alarm — decision first:** trust the provider broadcast, or
+  self-schedule via `AlarmManager.setExactAndAllowWhileIdle` for reliability?
+  If we self-schedule, declare `USE_EXACT_ALARM` (API 33+, auto-granted for
+  calendar/alarm-category apps, F-Droid-clean) with a `SCHEDULE_EXACT_ALARM`
+  fallback for API 31–32 (user-revocable → settings deep-link prompt).
+- **Battery-optimization exemption:** a *soft, optional* prompt via
+  `ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS` (settings deep-link — never the
+  auto-grant intent), honest copy: "Android may delay reminders to save battery;
+  exempt Calendula for on-time delivery." Shown once after the existing
+  `POST_NOTIFICATIONS` onboarding step, reversible in Settings → Notifications.
+- **Diagnostics:** a "send a test reminder in 1 minute" button in Notifications
+  settings so users can verify delivery on their specific OEM (Samsung / Xiaomi
+  are notorious for suppressing it).
+
+### Open decisions (resolve before building)
+
+1. Self-schedule via `AlarmManager` vs trust the provider broadcast
+   (reliability vs simplicity + battery cost).
+2. All-day reminder representation (minutes-before vs absolute time-of-day).
+3. Where per-calendar overrides live in the UI (rows on the Calendars screen vs
+   a list inside the Notifications sub-page).
+
+### Later (round two)
 
 - Snooze + dismiss actions on the notification (snooze needs an
-  exact-alarm / WorkManager decision)
-- Settings default reminder applied to new events
+  exact-alarm / WorkManager decision) — Tier 4 #13.
 
 ## Sharing & interop
 
@@ -312,8 +425,18 @@ whether drag-drop (#11) jumps ahead given its daily-driver impact.
 
 ## Platform & launchers
 
-- Home-screen widget *(was v3.0)*
-- App shortcuts (launcher long-press → New event), maybe a quick-settings tile
+- ~~Home-screen widget~~ **shipped v2.5.0** — agenda + month widgets
+- ~~App shortcuts (launcher long-press → New event)~~ **shipped v2.5.0** —
+  optional quick-settings tile still open
+
+## Quality & reliability
+
+- **Accessibility pass** — TalkBack content descriptions across all screens,
+  dynamic-type / large-font reflow, touch-target audit. Quality bar for an
+  F-Droid app; nothing tracks it yet.
+- **Reminder delivery reliability** — exact alarms + battery-optimization
+  exemption; specced in the "Reminders — defaults & delivery reliability" slice
+  above (Tier 4 #9).
 
 ## Locations & People *(go/no-go, captured 2026-06-11)*
 

CHANGELOG.md

@@ -7,6 +7,42 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.7.0] — 2026-06-18
+
+### Added
+- Share a single event as an `.ics` file from the event detail screen — hands a
+  standard calendar file to any app via the system share sheet.
+- Back up your local (device-only) calendars: Settings → Calendars → Export as
+  `.ics` file writes every event of your on-device calendars to a file you
+  choose. Local calendars aren't synced anywhere, so this is their only backup.
+- Open or share an `.ics` file into Calendula: a single event opens the create
+  form prefilled for review, while a file with many events (e.g. a backup) opens
+  a bulk import — pick a calendar and import them all. Re-importing a backup
+  won't create duplicates (events are matched by their unique identifier), and
+  anything Calendula can't represent (changed recurring occurrences, guest
+  lists) is reported rather than silently dropped.
+
+### Fixed
+- All-day events that cover a single day (e.g. a birthday) no longer show up on
+  the following day as well — in the day, week and month views or on the event
+  detail screen. The extra day came from interpreting the all-day date range in
+  the device's time zone instead of UTC.
+- Fixed the app crashing immediately on every launch in the optimized release
+  build: release code-shrinking (R8) was stripping a database class the
+  home-screen widget framework needs, so the app died at startup before showing
+  anything. Added the missing keep rule.
+
+## [2.6.0] — 2026-06-18
+
+### Added
+- App language can now be set from Android's system per-app language settings
+  (Android 13+), in addition to the in-app picker in Settings — and the app is
+  set up so further languages can be added by community translators
+
+### Fixed
+- Changing the app language in Settings now takes effect immediately; the
+  picker previously had no effect
+
 ## [2.5.0] — 2026-06-17
 
 ### Added

app/build.gradle.kts

@@ -28,8 +28,8 @@ android {
         // the tag, with versionCode = MAJOR*10000 + MINOR*100 + PATCH
         // (e.g. v2.0.0 -> 20000). These committed values are the dev/local
         // default; keep them matching the latest released tag. See docs/RELEASING.md.
-        versionCode = 20500
-        versionName = "2.5.0"
+        versionCode = 20700
+        versionName = "2.7.0"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }
@@ -78,6 +78,15 @@ android {
         }
     }
 
+    lint {
+        // Community translations are expected to be partial — a missing string
+        // falls back to the English base at runtime — so don't fail the build on
+        // it. Stale/extra keys (ExtraTranslation) stay fatal; scripts/
+        // check_translations.py guards the same invariants with clearer,
+        // translator-facing messages.
+        informational += "MissingTranslation"
+    }
+
     testOptions {
         unitTests {
             all { it.useJUnitPlatform() }

app/proguard-rules.pro

@@ -4,3 +4,14 @@
 
 # Compose Compiler may keep its own; defaults are fine
 -dontwarn org.jetbrains.annotations.**
+
+# Room database implementations (pulled in transitively via
+# androidx.glance:glance-appwidget → androidx.work → androidx.room).
+# The widgets rely on Glance, whose WorkManager backend stores state in a Room
+# database. Under R8 full mode (AGP 9 default) the generated *_Impl subclasses
+# of RoomDatabase lose their usable no-arg constructor / are marked abstract,
+# so Room's reflective instantiation throws InstantiationException and the app
+# crashes at startup with "Failed to create an instance of ...WorkDatabase".
+# Keep the generated Room database implementations fully intact.
+-keep class * extends androidx.room.RoomDatabase { *; }
+-dontwarn androidx.room.paging.**

app/src/main/AndroidManifest.xml

@@ -5,6 +5,13 @@
     <uses-permission android:name="android.permission.READ_CALENDAR" />
     <uses-permission android:name="android.permission.WRITE_CALENDAR" />
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+    <!--
+      Lets the "Reliable delivery" setting open the direct system dialog to
+      exempt Calendula from battery optimisation (so reminder broadcasts aren't
+      delayed by Doze). Used only to launch that dialog; falls back to the
+      battery-optimisation list if the OS declines the direct intent.
+    -->
+    <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />
 
     <!-- Package visibility (Android 11+): without this, getLaunchIntentForPackage
          returns null and the calendar manager's per-account "manage" button can't
@@ -25,6 +32,7 @@
         android:fullBackupContent="@xml/backup_rules"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
+        android:localeConfig="@xml/locales_config"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.Calendula"
@@ -39,6 +47,21 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
 
+            <!-- Open a .ics file (file manager / email attachment / browser). -->
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="content" android:mimeType="text/calendar" />
+                <data android:scheme="file" android:mimeType="text/calendar" />
+            </intent-filter>
+            <!-- Receive a .ics shared from another app. -->
+            <intent-filter>
+                <action android:name="android.intent.action.SEND" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <data android:mimeType="text/calendar" />
+            </intent-filter>
+
             <!-- Launcher long-press shortcuts (e.g. "New event"). -->
             <meta-data
                 android:name="android.app.shortcuts"
@@ -104,6 +127,19 @@
             </intent-filter>
         </receiver>
 
+        <!-- Hands .ics files we stage in the cache to other apps via a content
+             Uri (single-event share). Authority tracks applicationId so the
+             debug suffix doesn't break getUriForFile. -->
+        <provider
+            android:name="androidx.core.content.FileProvider"
+            android:authorities="${applicationId}.fileprovider"
+            android:exported="false"
+            android:grantUriPermissions="true">
+            <meta-data
+                android:name="android.support.FILE_PROVIDER_PATHS"
+                android:resource="@xml/file_paths" />
+        </provider>
+
         <!-- Persists the per-app language (M4) on API < 33, where the platform
              per-app-languages API is unavailable. On 33+ this is a no-op. -->
         <service

app/src/main/java/de/jeanlucmakiola/calendula/MainActivity.kt

@@ -2,16 +2,18 @@ package de.jeanlucmakiola.calendula
 
 import android.content.Context
 import android.content.Intent
+import android.net.Uri
 import android.os.Bundle
-import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
+import androidx.appcompat.app.AppCompatActivity
 import androidx.compose.foundation.isSystemInDarkTheme
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
+import androidx.core.content.IntentCompat
 import androidx.core.net.toUri
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
@@ -24,7 +26,7 @@ import de.jeanlucmakiola.calendula.ui.theme.CalendulaTheme
 import kotlinx.datetime.LocalDate
 
 @AndroidEntryPoint
-class MainActivity : ComponentActivity() {
+class MainActivity : AppCompatActivity() {
 
     // The occurrence a reminder notification was tapped for (eventId, begin,
     // end — the detail screen's key shape). singleTop + onNewIntent route a
@@ -35,11 +37,16 @@ class MainActivity : ComponentActivity() {
     // create). Consumed once by CalendarHost, same pattern as the detail key.
     private var requestedNav by mutableStateOf<WidgetNavRequest?>(null)
 
+    // An .ics file opened/shared into the app (ACTION_VIEW/SEND). Consumed once
+    // by CalendarHost's import flow.
+    private var requestedImportUri by mutableStateOf<Uri?>(null)
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
         requestedDetailKey = intent.detailKeyOrNull()
         requestedNav = intent.navRequestOrNull()
+        requestedImportUri = intent.importUriOrNull()
         setContent {
             // One activity-scoped SettingsViewModel drives both the theme here
             // and the Settings screen, so a theme change applies app-wide at once.
@@ -60,6 +67,8 @@ class MainActivity : ComponentActivity() {
                     onDetailKeyConsumed = { requestedDetailKey = null },
                     widgetNavRequest = requestedNav,
                     onWidgetNavConsumed = { requestedNav = null },
+                    requestedImportUri = requestedImportUri,
+                    onImportConsumed = { requestedImportUri = null },
                 )
             }
         }
@@ -69,6 +78,21 @@ class MainActivity : ComponentActivity() {
         super.onNewIntent(intent)
         intent.detailKeyOrNull()?.let { requestedDetailKey = it }
         intent.navRequestOrNull()?.let { requestedNav = it }
+        intent.importUriOrNull()?.let { requestedImportUri = it }
+    }
+
+    /**
+     * The `.ics` Uri an external app asked us to open (file manager `ACTION_VIEW`)
+     * or share into us (`ACTION_SEND`). Restricted to content/file schemes so the
+     * app's own `calendula://` deep-links never match.
+     */
+    private fun Intent.importUriOrNull(): Uri? {
+        val uri = when (action) {
+            Intent.ACTION_VIEW -> data
+            Intent.ACTION_SEND -> IntentCompat.getParcelableExtra(this, Intent.EXTRA_STREAM, Uri::class.java)
+            else -> null
+        } ?: return null
+        return uri.takeIf { it.scheme == "content" || it.scheme == "file" }
     }
 
     private fun Intent.navRequestOrNull(): WidgetNavRequest? = when {

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/AllDayReminderEncoding.kt

@@ -0,0 +1,70 @@
+package de.jeanlucmakiola.calendula.data.calendar
+
+import java.time.Instant
+import java.time.LocalDate
+import java.time.LocalTime
+import java.time.ZoneId
+import java.time.ZoneOffset
+import java.time.temporal.ChronoUnit
+
+/**
+ * Translates an all-day reminder between the **semantic** lead time the UI
+ * speaks (whole days before the event — "1 day before") and the **raw**
+ * `CalendarContract.Reminders.MINUTES` offset the provider stores.
+ *
+ * Calendula schedules no alarms itself: the provider fires a reminder at
+ * `DTSTART − MINUTES` (the Etar model). An all-day event's DTSTART is **UTC
+ * midnight** (see [EventWriteTimes]), so a raw `MINUTES = 1440` ("1 day") lands
+ * on UTC-midnight of the previous day — 02:00 local in CEST, not the morning.
+ *
+ * To fire at a chosen wall-clock time we encode that time *into* the offset:
+ * `MINUTES = UTC-midnight(startDate) − (localInstant of [timeOfDayMinutes] on the
+ * day [semanticMinutes] before)`. The single fixed offset can only be tuned for
+ * the event's own date, so a recurring all-day series or a post-creation
+ * timezone change drifts the fire time by the offset delta (±1h across DST) —
+ * an inherent limit of the provider model, shared by Etar.
+ */
+private const val MINUTES_PER_DAY = 1_440
+private const val MILLIS_PER_MINUTE = 60_000L
+
+/**
+ * Raw provider `MINUTES` for an all-day reminder set [semanticMinutes] before the
+ * event (a whole-day multiple; sub-day remainders are dropped), so it fires at
+ * [timeOfDayMinutes] (minutes from local midnight) in [zone]. The result may be
+ * **negative** — e.g. "at time of event" at 09:00 CEST encodes to −420, meaning
+ * the provider fires *after* DTSTART; this is valid and must not be clamped.
+ * A negative [semanticMinutes] is the "provider default" sentinel and passes
+ * through unchanged.
+ */
+internal fun toProviderAllDayMinutes(
+    semanticMinutes: Int,
+    startDate: LocalDate,
+    zone: ZoneId,
+    timeOfDayMinutes: Int,
+): Int {
+    if (semanticMinutes < 0) return semanticMinutes
+    val utcMidnight = startDate.atStartOfDay(ZoneOffset.UTC).toInstant().toEpochMilli()
+    val fire = startDate.minusDays((semanticMinutes / MINUTES_PER_DAY).toLong())
+        .atTime(LocalTime.of(timeOfDayMinutes / 60, timeOfDayMinutes % 60))
+        .atZone(zone).toInstant().toEpochMilli()
+    return ((utcMidnight - fire) / MILLIS_PER_MINUTE).toInt()
+}
+
+/**
+ * Recover the semantic whole-day lead time from a raw all-day reminder
+ * [rawMinutes]. Keys off the **local date** of the encoded fire instant, so it
+ * returns the right day count regardless of which [timeOfDayMinutes] wrote the
+ * row — including pre-feature rows (raw multiples of 1440, fired at UTC midnight)
+ * and rows written under a different timezone. A negative [rawMinutes] (fire
+ * after DTSTART) folds to day 0.
+ */
+internal fun fromProviderAllDayMinutes(
+    rawMinutes: Int,
+    startDate: LocalDate,
+    zone: ZoneId,
+): Int {
+    val utcMidnight = startDate.atStartOfDay(ZoneOffset.UTC).toInstant().toEpochMilli()
+    val fireLocalDate = Instant.ofEpochMilli(utcMidnight - rawMinutes * MILLIS_PER_MINUTE)
+        .atZone(zone).toLocalDate()
+    return ChronoUnit.DAYS.between(fireLocalDate, startDate).toInt() * MINUTES_PER_DAY
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarDataSource.kt

@@ -18,10 +18,15 @@ import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventDetail
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
+import de.jeanlucmakiola.calendula.domain.EventStatus
 import de.jeanlucmakiola.calendula.domain.Reminder
+import de.jeanlucmakiola.calendula.domain.ics.IcsEvent
+import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
 import de.jeanlucmakiola.calendula.domain.rruleTruncatedAt
+import kotlinx.datetime.toJavaLocalDate
 import java.time.ZoneId
 import java.time.ZoneOffset
+import java.util.UUID
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -47,6 +52,26 @@ interface CalendarDataSource {
      */
     fun eventColorPalette(calendarId: Long): List<EventColorOption>
 
+    /**
+     * Every master/one-off event of the writable local calendars, mapped for a
+     * whole-calendar `.ics` backup. Modified-occurrence and cancelled-exception
+     * rows are excluded (see [EventExportProjection]).
+     */
+    fun exportableEvents(): List<IcsEvent>
+
+    /**
+     * The non-empty `Events.UID_2445` values present in [calendarId] — used to
+     * dedup an `.ics` import so re-importing a backup doesn't double events.
+     */
+    fun existingUids(calendarId: Long): Set<String>
+
+    /**
+     * Insert a parsed `.ics` event into [calendarId], preserving its UID (or
+     * minting one when absent); returns the new `Events._ID`. Reminders are
+     * written as the file's raw lead minutes (METHOD_ALERT).
+     */
+    fun insertImportedEvent(event: ParsedIcsEvent, calendarId: Long): Long
+
     /**
      * Create a new device-only (`ACCOUNT_TYPE_LOCAL`) calendar the app owns;
      * returns its `Calendars._ID`. Inserted through the sync-adapter URI so the
@@ -60,24 +85,40 @@ interface CalendarDataSource {
     /** Permanently delete a local calendar the app owns, with all its events. */
     fun deleteCalendar(id: Long)
 
-    /** Insert a new event; returns the new `Events._ID`. */
-    fun insertEvent(form: EventForm): Long
+    /**
+     * Insert a new event; returns the new `Events._ID`. [allDayReminderTimeMinutes]
+     * (minutes from local midnight) is the wall-clock time all-day reminders
+     * should fire at — encoded into each all-day reminder's provider offset
+     * (ignored for timed events).
+     */
+    fun insertEvent(form: EventForm, allDayReminderTimeMinutes: Int): Long
 
     /**
      * Update an existing event (for recurring events: the whole series) to
      * match [updated]. [original] is the form as it was prefilled from the
      * event, so only fields the user actually changed are written and the
      * reminder rows can be diffed instead of wiped.
+     * [allDayReminderTimeMinutes]: see [insertEvent].
      */
-    fun updateEvent(eventId: Long, original: EventForm, updated: EventForm)
+    fun updateEvent(
+        eventId: Long,
+        original: EventForm,
+        updated: EventForm,
+        allDayReminderTimeMinutes: Int,
+    )
 
     /**
      * Change a single occurrence of a recurring event by inserting a
      * modified-occurrence exception at [beginMillis] (the occurrence's
      * `Instances.BEGIN`) carrying [form]'s values; returns the exception
-     * row's `Events._ID`.
+     * row's `Events._ID`. [allDayReminderTimeMinutes]: see [insertEvent].
      */
-    fun updateOccurrence(eventId: Long, beginMillis: Long, form: EventForm): Long
+    fun updateOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        form: EventForm,
+        allDayReminderTimeMinutes: Int,
+    ): Long
 
     /**
      * Change a recurring event from the occurrence at [beginMillis] onwards
@@ -92,6 +133,7 @@ interface CalendarDataSource {
         beginMillis: Long,
         original: EventForm,
         updated: EventForm,
+        allDayReminderTimeMinutes: Int,
     ): Long
 
     /**
@@ -247,6 +289,112 @@ class AndroidCalendarDataSource @Inject constructor(
             ?: emptyList()
     }
 
+    override fun exportableEvents(): List<IcsEvent> {
+        // Only the local calendars the app owns and can write — synced calendars
+        // already have a backup (their server). Map id → display name for the
+        // X-CALENDULA-CALENDAR tag a restore uses to fan back out.
+        val names = calendars()
+            .filter { it.isLocal && it.canModifyContents }
+            .associate { it.id to it.displayName }
+        if (names.isEmpty()) return emptyList()
+
+        val idList = names.keys.joinToString(",")
+        return resolver.query(
+            CalendarContract.Events.CONTENT_URI,
+            EventExportProjection.COLUMNS,
+            // Skip soft-deleted rows and exception rows (modified occurrences /
+            // cancellations) — v1 exports masters + one-offs only.
+            "${CalendarContract.Events.CALENDAR_ID} IN ($idList) AND " +
+                "${CalendarContract.Events.DELETED} = 0 AND " +
+                "${CalendarContract.Events.ORIGINAL_ID} IS NULL",
+            null,
+            CalendarContract.Events.DTSTART + " ASC",
+        )?.use { c ->
+            c.mapAll {
+                val reader = CursorColumnReader(c)
+                val eventId = reader.getLong(EventExportProjection.IDX_ID)
+                val calendarId = reader.getLong(EventExportProjection.IDX_CALENDAR_ID)
+                reader.toIcsEvent(
+                    reminderMinutes = queryReminders(eventId).map { it.minutes },
+                    calendarName = names[calendarId],
+                )
+            }
+        } ?: emptyList()
+    }
+
+    override fun existingUids(calendarId: Long): Set<String> = resolver.query(
+        CalendarContract.Events.CONTENT_URI,
+        arrayOf(CalendarContract.Events.UID_2445),
+        "${CalendarContract.Events.CALENDAR_ID} = ? AND " +
+            "${CalendarContract.Events.UID_2445} IS NOT NULL",
+        arrayOf(calendarId.toString()),
+        null,
+    )?.use { c ->
+        buildSet { while (c.moveToNext()) c.getString(0)?.takeIf { it.isNotEmpty() }?.let(::add) }
+    } ?: emptySet()
+
+    override fun insertImportedEvent(event: ParsedIcsEvent, calendarId: Long): Long {
+        val startMillis = event.start.toEpochMillis()
+        val endMillis = event.end.toEpochMillis()
+        val values = ContentValues().apply {
+            put(CalendarContract.Events.CALENDAR_ID, calendarId)
+            // Preserve the file's UID so a re-import dedups against it; mint one
+            // only when the source event carried none.
+            put(
+                CalendarContract.Events.UID_2445,
+                event.uid?.takeIf { it.isNotBlank() } ?: "${UUID.randomUUID()}@calendula",
+            )
+            put(CalendarContract.Events.TITLE, event.summary.trim())
+            put(CalendarContract.Events.ALL_DAY, if (event.isAllDay) 1 else 0)
+            put(CalendarContract.Events.DTSTART, startMillis)
+            if (event.recurrenceRule == null) {
+                put(CalendarContract.Events.DTEND, endMillis)
+            } else {
+                put(CalendarContract.Events.RRULE, event.recurrenceRule)
+                put(
+                    CalendarContract.Events.DURATION,
+                    importDuration(startMillis, endMillis, event.isAllDay),
+                )
+            }
+            // All-day rows live at UTC midnights (the file already encodes them so);
+            // timed rows keep the event's own zone.
+            put(CalendarContract.Events.EVENT_TIMEZONE, if (event.isAllDay) "UTC" else event.zoneId)
+            put(CalendarContract.Events.AVAILABILITY, event.availability.toProviderValue())
+            put(CalendarContract.Events.STATUS, event.status.toProviderStatus())
+            event.location?.trim()?.takeIf { it.isNotEmpty() }
+                ?.let { put(CalendarContract.Events.EVENT_LOCATION, it) }
+            event.description?.trim()?.takeIf { it.isNotEmpty() }
+                ?.let { put(CalendarContract.Events.DESCRIPTION, it) }
+        }
+        val uri = resolver.insert(CalendarContract.Events.CONTENT_URI, values)
+            ?: throw WriteFailedException("import event into calendar id=$calendarId")
+        val eventId = ContentUris.parseId(uri)
+        // Raw lead minutes straight from the file's VALARMs (best-effort, like insertEvent).
+        event.reminderMinutes.distinct().filter { it >= 0 }.forEach { minutes ->
+            val reminder = ContentValues().apply {
+                put(CalendarContract.Reminders.EVENT_ID, eventId)
+                put(CalendarContract.Reminders.MINUTES, minutes)
+                put(CalendarContract.Reminders.METHOD, CalendarContract.Reminders.METHOD_ALERT)
+            }
+            if (resolver.insert(CalendarContract.Reminders.CONTENT_URI, reminder) == null) {
+                Log.w(TAG, "Failed to attach reminder ($minutes min) to imported event $eventId")
+            }
+        }
+        return eventId
+    }
+
+    /** Provider DURATION for an imported recurring row: whole days / seconds. */
+    private fun importDuration(startMillis: Long, endMillis: Long, isAllDay: Boolean): String {
+        val span = (endMillis - startMillis).coerceAtLeast(0)
+        return if (isAllDay) "P${span / 86_400_000L}D" else "P${span / 1_000L}S"
+    }
+
+    private fun EventStatus.toProviderStatus(): Int = when (this) {
+        EventStatus.Confirmed -> CalendarContract.Events.STATUS_CONFIRMED
+        EventStatus.Tentative -> CalendarContract.Events.STATUS_TENTATIVE
+        EventStatus.Cancelled -> CalendarContract.Events.STATUS_CANCELED
+    }
+
     /** The account a calendar belongs to, for scoping a `Colors` lookup. */
     private fun calendarAccount(calendarId: Long): CalendarAccount? = resolver.query(
         ContentUris.withAppendedId(CalendarContract.Calendars.CONTENT_URI, calendarId),
@@ -265,13 +413,44 @@ class AndroidCalendarDataSource @Inject constructor(
 
     private data class CalendarAccount(val name: String, val type: String)
 
-    override fun insertEvent(form: EventForm): Long {
+    /**
+     * The raw provider `MINUTES` to store for one of [form]'s reminders: an
+     * all-day reminder is shifted to fire at [allDayReminderTimeMinutes] local
+     * (see [toProviderAllDayMinutes]); a timed reminder is its lead time as-is.
+     */
+    private fun providerReminderMinutes(
+        form: EventForm,
+        minutes: Int,
+        allDayReminderTimeMinutes: Int,
+    ): Int = if (form.isAllDay) {
+        toProviderAllDayMinutes(
+            semanticMinutes = minutes,
+            startDate = form.start.date.toJavaLocalDate(),
+            zone = ZoneId.systemDefault(),
+            timeOfDayMinutes = allDayReminderTimeMinutes,
+        )
+    } else {
+        minutes
+    }
+
+    /** [form]'s reminders as the distinct raw provider offsets to store. */
+    private fun encodedReminders(form: EventForm, allDayReminderTimeMinutes: Int): List<Int> =
+        form.reminders
+            .map { providerReminderMinutes(form, it, allDayReminderTimeMinutes) }
+            .distinct()
+
+    override fun insertEvent(form: EventForm, allDayReminderTimeMinutes: Int): Long {
         val times = form.toWriteTimes(ZoneId.systemDefault())
         val values = ContentValues().apply {
             put(
                 CalendarContract.Events.CALENDAR_ID,
                 requireNotNull(form.calendarId) { "EventForm.calendarId is required" },
             )
+            // A globally-unique UID so a later .ics backup/restore can identify
+            // the event and not duplicate it on re-import (the provider leaves
+            // this null for events it didn't sync). Older rows without one fall
+            // back to a stable synthesised UID at export time (deriveIcsUid).
+            put(CalendarContract.Events.UID_2445, "${UUID.randomUUID()}@calendula")
             put(CalendarContract.Events.TITLE, form.title.trim())
             put(CalendarContract.Events.ALL_DAY, if (form.isAllDay) 1 else 0)
             put(CalendarContract.Events.DTSTART, times.dtStartMillis)
@@ -303,20 +482,26 @@ class AndroidCalendarDataSource @Inject constructor(
         val eventId = ContentUris.parseId(uri)
         // Best effort (spec §8): the event exists at this point — a reminder
         // that fails to attach is logged, not surfaced as a failed create.
-        form.reminders.distinct().forEach { minutes ->
-            val reminder = ContentValues().apply {
-                put(CalendarContract.Reminders.EVENT_ID, eventId)
-                put(CalendarContract.Reminders.MINUTES, minutes)
-                put(CalendarContract.Reminders.METHOD, CalendarContract.Reminders.METHOD_ALERT)
+        encodedReminders(form, allDayReminderTimeMinutes)
+            .forEach { minutes ->
+                val reminder = ContentValues().apply {
+                    put(CalendarContract.Reminders.EVENT_ID, eventId)
+                    put(CalendarContract.Reminders.MINUTES, minutes)
+                    put(CalendarContract.Reminders.METHOD, CalendarContract.Reminders.METHOD_ALERT)
+                }
+                if (resolver.insert(CalendarContract.Reminders.CONTENT_URI, reminder) == null) {
+                    Log.w(TAG, "Failed to attach reminder ($minutes min) to event $eventId")
+                }
             }
-            if (resolver.insert(CalendarContract.Reminders.CONTENT_URI, reminder) == null) {
-                Log.w(TAG, "Failed to attach reminder ($minutes min) to event $eventId")
-            }
-        }
         return eventId
     }
 
-    override fun updateEvent(eventId: Long, original: EventForm, updated: EventForm) {
+    override fun updateEvent(
+        eventId: Long,
+        original: EventForm,
+        updated: EventForm,
+        allDayReminderTimeMinutes: Int,
+    ) {
         val values = buildEventUpdateValues(
             original = original,
             updated = updated,
@@ -332,13 +517,19 @@ class AndroidCalendarDataSource @Inject constructor(
             if (rows == 0) throw WriteFailedException("update event id=$eventId")
         }
         // Untouched reminder sets are left alone so unrelated edits can't
-        // disturb provider rows the form never knew about.
+        // disturb provider rows the form never knew about. The diff is on the
+        // form's semantic minutes; reconcile works in encoded provider minutes.
         if (updated.reminders.toSet() != original.reminders.toSet()) {
-            reconcileReminders(eventId, updated.reminders)
+            reconcileReminders(eventId, encodedReminders(updated, allDayReminderTimeMinutes))
         }
     }
 
-    override fun updateOccurrence(eventId: Long, beginMillis: Long, form: EventForm): Long {
+    override fun updateOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        form: EventForm,
+        allDayReminderTimeMinutes: Int,
+    ): Long {
         // The provider clones the series row and applies these values on top.
         val values = buildOccurrenceExceptionValues(
             form = form,
@@ -352,7 +543,7 @@ class AndroidCalendarDataSource @Inject constructor(
         val exceptionId = ContentUris.parseId(uri)
         // Whether the provider copied the parent's reminder rows is its
         // business — reconciling against the actual rows handles both ways.
-        reconcileReminders(exceptionId, form.reminders)
+        reconcileReminders(exceptionId, encodedReminders(form, allDayReminderTimeMinutes))
         return exceptionId
     }
 
@@ -361,16 +552,17 @@ class AndroidCalendarDataSource @Inject constructor(
         beginMillis: Long,
         original: EventForm,
         updated: EventForm,
+        allDayReminderTimeMinutes: Int,
     ): Long {
         val row = querySeriesRow(eventId)
         // From the first occurrence on (or with no rule to split) this is
         // just a series update.
         if (row.rrule.isNullOrBlank() || beginMillis <= row.dtStartMillis) {
-            updateEvent(eventId, original, updated)
+            updateEvent(eventId, original, updated, allDayReminderTimeMinutes)
             return eventId
         }
         // Insert the new series first: if it fails, the original is untouched.
-        val newEventId = insertEvent(updated)
+        val newEventId = insertEvent(updated, allDayReminderTimeMinutes)
         truncateSeries(eventId, row, beginMillis)
         return newEventId
     }
@@ -456,9 +648,11 @@ class AndroidCalendarDataSource @Inject constructor(
     }
 
     /**
-     * Make the event's reminder rows match [targetMinutes]: rows with other
-     * lead times are deleted, missing ones inserted as best-effort ALERTs
-     * (like insertEvent). Rows whose minutes survive keep their method.
+     * Make the event's reminder rows match [targetMinutes] — the raw provider
+     * offsets to store (already encoded via [encodedReminders], so all-day shifts
+     * are baked in and the diff matches the stored rows). Rows with other offsets
+     * are deleted, missing ones inserted as best-effort ALERTs (like insertEvent).
+     * Rows whose minutes survive keep their method.
      */
     private fun reconcileReminders(eventId: Long, targetMinutes: List<Int>) {
         val target = targetMinutes.toSet()

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepository.kt

@@ -5,6 +5,9 @@ import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventDetail
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
+import de.jeanlucmakiola.calendula.domain.ics.IcsEvent
+import de.jeanlucmakiola.calendula.domain.ics.IcsImportSummary
+import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
 import kotlinx.coroutines.flow.Flow
 import kotlin.time.Instant
 
@@ -28,6 +31,19 @@ interface CalendarRepository {
     /** Permanently delete a local calendar the app owns, with all its events. */
     suspend fun deleteCalendar(id: Long)
 
+    /**
+     * Every event of the writable local calendars, ready to serialise into a
+     * whole-calendar `.ics` backup (see [CalendarDataSource.exportableEvents]).
+     */
+    suspend fun exportEvents(): List<IcsEvent>
+
+    /**
+     * Bulk-import parsed `.ics` [events] into [targetCalendarId]. Events whose
+     * UID already exists in the target are skipped (idempotent restore); the
+     * rest are inserted. See [CalendarDataSource.insertImportedEvent].
+     */
+    suspend fun importEvents(targetCalendarId: Long, events: List<ParsedIcsEvent>): IcsImportSummary
+
     /** Create a new event from a validated form; returns the new `Events._ID`. */
     suspend fun createEvent(form: EventForm): Long
 

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImpl.kt

@@ -2,15 +2,19 @@ package de.jeanlucmakiola.calendula.data.calendar
 
 import de.jeanlucmakiola.calendula.data.di.IoDispatcher
 import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
+import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventDetail
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
+import de.jeanlucmakiola.calendula.domain.ics.IcsImportSummary
+import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.onStart
@@ -28,9 +32,14 @@ import javax.inject.Singleton
 class CalendarRepositoryImpl @Inject constructor(
     private val dataSource: CalendarDataSource,
     private val prefs: CalendarPrefs,
+    private val settingsPrefs: SettingsPrefs,
     @IoDispatcher private val io: CoroutineDispatcher,
 ) : CalendarRepository {
 
+    /** The configured wall-clock fire time for all-day reminders, read per write. */
+    private suspend fun allDayReminderTimeMinutes(): Int =
+        settingsPrefs.allDayReminderTimeMinutes.first()
+
     private val ticks = MutableSharedFlow<Unit>(
         replay = 0,
         extraBufferCapacity = 1,
@@ -92,8 +101,30 @@ class CalendarRepositoryImpl @Inject constructor(
     override suspend fun deleteCalendar(id: Long) =
         withContext(io) { dataSource.deleteCalendar(id) }
 
+    override suspend fun exportEvents() = withContext(io) { dataSource.exportableEvents() }
+
+    override suspend fun importEvents(
+        targetCalendarId: Long,
+        events: List<ParsedIcsEvent>,
+    ): IcsImportSummary = withContext(io) {
+        val existing = dataSource.existingUids(targetCalendarId)
+        var imported = 0
+        var skipped = 0
+        for (event in events) {
+            // A known UID means the event is already in this calendar — skip,
+            // keeping a restore idempotent (no overwrite this pass).
+            if (event.uid != null && event.uid in existing) {
+                skipped++
+            } else {
+                dataSource.insertImportedEvent(event, targetCalendarId)
+                imported++
+            }
+        }
+        IcsImportSummary(imported = imported, skippedDuplicate = skipped)
+    }
+
     override suspend fun createEvent(form: EventForm): Long = withContext(io) {
-        dataSource.insertEvent(form)
+        dataSource.insertEvent(form, allDayReminderTimeMinutes())
     }
 
     override suspend fun updateEvent(
@@ -101,7 +132,7 @@ class CalendarRepositoryImpl @Inject constructor(
         original: EventForm,
         updated: EventForm,
     ) = withContext(io) {
-        dataSource.updateEvent(eventId, original, updated)
+        dataSource.updateEvent(eventId, original, updated, allDayReminderTimeMinutes())
     }
 
     override suspend fun deleteEvent(eventId: Long) = withContext(io) {
@@ -113,7 +144,7 @@ class CalendarRepositoryImpl @Inject constructor(
         beginMillis: Long,
         form: EventForm,
     ): Long = withContext(io) {
-        dataSource.updateOccurrence(eventId, beginMillis, form)
+        dataSource.updateOccurrence(eventId, beginMillis, form, allDayReminderTimeMinutes())
     }
 
     override suspend fun updateEventFromOccurrence(
@@ -122,7 +153,9 @@ class CalendarRepositoryImpl @Inject constructor(
         original: EventForm,
         updated: EventForm,
     ): Long = withContext(io) {
-        dataSource.updateEventFromOccurrence(eventId, beginMillis, original, updated)
+        dataSource.updateEventFromOccurrence(
+            eventId, beginMillis, original, updated, allDayReminderTimeMinutes(),
+        )
     }
 
     override suspend fun deleteOccurrence(eventId: Long, beginMillis: Long) = withContext(io) {

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/EventDetailMapper.kt

@@ -13,6 +13,9 @@ import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.domain.EventStatus
 import de.jeanlucmakiola.calendula.domain.Reminder
 import de.jeanlucmakiola.calendula.domain.ReminderMethod
+import java.time.Instant
+import java.time.ZoneId
+import java.time.ZoneOffset
 
 private const val TAG = "EventDetailMapper"
 
@@ -58,6 +61,7 @@ internal fun ColumnReader.toEventDetailCore(
     val color = eventColor ?: getInt(EventDetailProjection.IDX_CALENDAR_COLOR)
 
     val eventId = getLong(EventDetailProjection.IDX_EVENT_ID)
+    val isAllDay = getInt(EventDetailProjection.IDX_ALL_DAY) != 0
     val instance = EventInstance(
         instanceId = eventId,
         eventId = eventId,
@@ -65,11 +69,23 @@ internal fun ColumnReader.toEventDetailCore(
         title = title,
         start = begin.toKotlinInstantFromEpochMillis(),
         end = end.toKotlinInstantFromEpochMillis(),
-        isAllDay = getInt(EventDetailProjection.IDX_ALL_DAY) != 0,
+        isAllDay = isAllDay,
         color = color,
         location = getString(EventDetailProjection.IDX_LOCATION),
     )
 
+    // All-day reminders are stored as a wall-clock-shifted offset (see
+    // AllDayReminderEncoding); decode back to the whole-day lead time the form
+    // and detail screen speak. DTSTART is UTC midnight for all-day events, so the
+    // event's date is its UTC date.
+    val displayReminders = if (isAllDay) {
+        val startDate = Instant.ofEpochMilli(begin).atZone(ZoneOffset.UTC).toLocalDate()
+        val zone = ZoneId.systemDefault()
+        reminders.map { it.copy(minutes = fromProviderAllDayMinutes(it.minutes, startDate, zone)) }
+    } else {
+        reminders
+    }
+
     // STATUS shares its 0 value with STATUS_TENTATIVE, so a missing column must
     // be distinguished from a present 0 — an absent status means "just confirmed".
     val status = if (isNull(EventDetailProjection.IDX_STATUS)) {
@@ -84,7 +100,7 @@ internal fun ColumnReader.toEventDetailCore(
         organizer = getString(EventDetailProjection.IDX_ORGANIZER),
         attendees = attendees,
         rrule = getString(EventDetailProjection.IDX_RRULE),
-        reminders = reminders,
+        reminders = displayReminders,
         status = status,
         // BUSY and DEFAULT are both 0, so a null column folds into the same
         // default these mappers already return — no isNull guard needed.

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/IcsExportMapper.kt

@@ -0,0 +1,54 @@
+package de.jeanlucmakiola.calendula.data.calendar
+
+import de.jeanlucmakiola.calendula.domain.EventStatus
+import de.jeanlucmakiola.calendula.domain.ics.IcsEvent
+import de.jeanlucmakiola.calendula.domain.ics.deriveIcsUid
+import de.jeanlucmakiola.calendula.domain.ics.parseRfc2445DurationMillis
+
+/**
+ * Map one Events row (read through [EventExportProjection]) into an [IcsEvent]
+ * for backup. [reminderMinutes] are the row's raw provider reminder offsets and
+ * [calendarName] the display name of its calendar (emitted as
+ * `X-CALENDULA-CALENDAR`). Pure given a [ColumnReader] — JVM-tested with
+ * MapColumnReader.
+ */
+internal fun ColumnReader.toIcsEvent(
+    reminderMinutes: List<Int>,
+    calendarName: String?,
+): IcsEvent {
+    val eventId = getLong(EventExportProjection.IDX_ID)
+    val dtStart = getLong(EventExportProjection.IDX_DTSTART)
+    val rrule = getString(EventExportProjection.IDX_RRULE)?.takeIf { it.isNotBlank() }
+
+    // Recurring rows store DURATION instead of DTEND; reconstruct the end from it
+    // so the writer can render DTEND. A missing/blank both means a zero-length event.
+    val end = when {
+        !isNull(EventExportProjection.IDX_DTEND) -> getLong(EventExportProjection.IDX_DTEND)
+        else -> dtStart + parseRfc2445DurationMillis(getString(EventExportProjection.IDX_DURATION))
+    }
+
+    // STATUS shares value 0 with TENTATIVE, so an absent column must read as Confirmed.
+    val status = if (isNull(EventExportProjection.IDX_STATUS)) {
+        EventStatus.Confirmed
+    } else {
+        mapEventStatus(getInt(EventExportProjection.IDX_STATUS))
+    }
+
+    return IcsEvent(
+        uid = deriveIcsUid(getString(EventExportProjection.IDX_UID), eventId, dtStart),
+        summary = getString(EventExportProjection.IDX_TITLE).orEmpty(),
+        start = dtStart.toKotlinInstantFromEpochMillis(),
+        end = end.toKotlinInstantFromEpochMillis(),
+        isAllDay = getInt(EventExportProjection.IDX_ALL_DAY) != 0,
+        zoneId = getString(EventExportProjection.IDX_EVENT_TIMEZONE)?.takeIf { it.isNotBlank() }
+            ?: "UTC",
+        recurrenceRule = rrule,
+        location = getString(EventExportProjection.IDX_LOCATION),
+        description = getString(EventExportProjection.IDX_DESCRIPTION),
+        reminderMinutes = reminderMinutes,
+        status = status,
+        availability = mapAvailability(getInt(EventExportProjection.IDX_AVAILABILITY)),
+        calendarName = calendarName,
+    )
+}
+

app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/Projections.kt

@@ -97,6 +97,48 @@ internal object EventDetailProjection {
     const val IDX_EVENT_COLOR_KEY = 17
 }
 
+/**
+ * Master/one-off Events rows for a whole-calendar backup. Unlike
+ * [EventDetailProjection] this reads `UID_2445` (to keep a row's identity across
+ * backups) and `DURATION` (recurring rows carry it instead of DTEND). Modified-
+ * occurrence and cancelled-exception rows are filtered out by the query
+ * (`ORIGINAL_ID IS NULL`), so RECURRENCE-ID overrides and EXDATEs aren't
+ * exported yet — a documented v1 limit (import skips them too).
+ */
+internal object EventExportProjection {
+    val COLUMNS: Array<String> = arrayOf(
+        CalendarContract.Events._ID,
+        CalendarContract.Events.UID_2445,
+        CalendarContract.Events.TITLE,
+        CalendarContract.Events.DTSTART,
+        CalendarContract.Events.DTEND,
+        CalendarContract.Events.DURATION,
+        CalendarContract.Events.ALL_DAY,
+        CalendarContract.Events.EVENT_TIMEZONE,
+        CalendarContract.Events.RRULE,
+        CalendarContract.Events.EVENT_LOCATION,
+        CalendarContract.Events.DESCRIPTION,
+        CalendarContract.Events.STATUS,
+        CalendarContract.Events.AVAILABILITY,
+        CalendarContract.Events.CALENDAR_ID,
+    )
+
+    const val IDX_ID = 0
+    const val IDX_UID = 1
+    const val IDX_TITLE = 2
+    const val IDX_DTSTART = 3
+    const val IDX_DTEND = 4
+    const val IDX_DURATION = 5
+    const val IDX_ALL_DAY = 6
+    const val IDX_EVENT_TIMEZONE = 7
+    const val IDX_RRULE = 8
+    const val IDX_LOCATION = 9
+    const val IDX_DESCRIPTION = 10
+    const val IDX_STATUS = 11
+    const val IDX_AVAILABILITY = 12
+    const val IDX_CALENDAR_ID = 13
+}
+
 internal object AttendeeProjection {
     val COLUMNS: Array<String> = arrayOf(
         CalendarContract.Attendees.ATTENDEE_NAME,

app/src/main/java/de/jeanlucmakiola/calendula/data/ics/IcsExporter.kt

@@ -0,0 +1,45 @@
+package de.jeanlucmakiola.calendula.data.ics
+
+import android.content.Context
+import android.net.Uri
+import androidx.core.content.FileProvider
+import dagger.hilt.android.qualifiers.ApplicationContext
+import java.io.File
+import java.io.IOException
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * The Android IO edge of `.ics` export: writes a serialised calendar to a
+ * SAF document (whole-calendar backup) or stages it in a cache file behind a
+ * `FileProvider` content Uri (single-event share). The serialisation itself is
+ * the pure `domain.ics.IcsWriter`; this class only moves bytes.
+ */
+@Singleton
+class IcsExporter @Inject constructor(
+    @ApplicationContext private val context: Context,
+) {
+
+    /** Write [content] to the SAF document at [uri] as UTF-8. Throws on failure. */
+    fun writeDocument(uri: Uri, content: String) {
+        context.contentResolver.openOutputStream(uri)?.use { out ->
+            out.write(content.toByteArray(Charsets.UTF_8))
+        } ?: throw IOException("Could not open $uri for writing")
+    }
+
+    /**
+     * Stage [content] in a private cache file and return a shareable content
+     * Uri for an `ACTION_SEND`. [fileName] is the suggested `.ics` name shown to
+     * the receiving app. The authority mirrors the manifest's `FileProvider`.
+     */
+    fun stageShareFile(fileName: String, content: String): Uri {
+        val dir = File(context.cacheDir, SHARE_DIR).apply { mkdirs() }
+        val file = File(dir, fileName)
+        file.writeText(content, Charsets.UTF_8)
+        return FileProvider.getUriForFile(context, "${context.packageName}.fileprovider", file)
+    }
+
+    private companion object {
+        const val SHARE_DIR = "shared_ics"
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/ics/IcsImporter.kt

@@ -0,0 +1,21 @@
+package de.jeanlucmakiola.calendula.data.ics
+
+import android.content.Context
+import android.net.Uri
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Android IO edge of `.ics` import: reads the text of a received/opened
+ * document [Uri]. Parsing is the pure `domain.ics.IcsParser`; this class only
+ * pulls bytes off the ContentResolver. Returns null on any read failure.
+ */
+@Singleton
+class IcsImporter @Inject constructor(
+    @ApplicationContext private val context: Context,
+) {
+    fun readText(uri: Uri): String? = runCatching {
+        context.contentResolver.openInputStream(uri)?.use { it.readBytes().toString(Charsets.UTF_8) }
+    }.getOrNull()
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/prefs/SettingsPrefs.kt

@@ -4,6 +4,7 @@ import androidx.datastore.core.DataStore
 import androidx.datastore.preferences.core.Preferences
 import androidx.datastore.preferences.core.booleanPreferencesKey
 import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.intPreferencesKey
 import androidx.datastore.preferences.core.stringPreferencesKey
 import de.jeanlucmakiola.calendula.domain.EventFormField
 import kotlinx.coroutines.flow.Flow
@@ -127,6 +128,97 @@ class SettingsPrefs @Inject constructor(
         store.edit { it[REMINDER_ONBOARDING_KEY] = true }
     }
 
+    /**
+     * The default reminder lead time (minutes before start) prefilled on new
+     * **timed** events. `null` = no default reminder — the prior behaviour, kept
+     * as the factory default so existing users aren't surprised by reminders they
+     * never asked for. Stored as a string so "none" is distinct from a numeric
+     * value (and from an unset key, which is also "none"). Per-calendar overrides
+     * in [perCalendarReminderOverride] take precedence; all-day events instead use
+     * [defaultAllDayReminderMinutes]. Resolve with [resolveDefaultReminder].
+     */
+    val defaultReminderMinutes: Flow<Int?> = store.data.map { prefs ->
+        prefs[DEFAULT_REMINDER_KEY].toReminderMinutes()
+    }
+
+    suspend fun setDefaultReminderMinutes(minutes: Int?) {
+        store.edit { it[DEFAULT_REMINDER_KEY] = minutes?.toString() ?: NONE }
+    }
+
+    /**
+     * The default reminder lead time prefilled on new **all-day** events, in
+     * minutes before the start of the day. All-day events want day-scale lead
+     * times ("1 day before"), so they have their own default rather than reusing
+     * the timed one. `null` = no default. Per-calendar overrides do **not** apply
+     * to all-day events — they always use this global value.
+     */
+    val defaultAllDayReminderMinutes: Flow<Int?> = store.data.map { prefs ->
+        prefs[DEFAULT_ALLDAY_REMINDER_KEY].toReminderMinutes()
+    }
+
+    suspend fun setDefaultAllDayReminderMinutes(minutes: Int?) {
+        store.edit { it[DEFAULT_ALLDAY_REMINDER_KEY] = minutes?.toString() ?: NONE }
+    }
+
+    /**
+     * Wall-clock time, as minutes from local midnight, at which **all-day**
+     * reminders fire. All-day events live at UTC midnight, so a raw "1 day
+     * before" would fire at an off hour (02:00 local in CEST); this time is
+     * encoded into the provider offset so the reminder lands at, e.g., 09:00 the
+     * day before instead. Global for every all-day reminder; default 09:00.
+     * Stored/clamped to a valid 0..1439 minute-of-day.
+     */
+    val allDayReminderTimeMinutes: Flow<Int> = store.data.map { prefs ->
+        (prefs[ALLDAY_REMINDER_TIME_KEY] ?: DEFAULT_ALLDAY_REMINDER_TIME)
+            .coerceIn(0, MINUTES_PER_DAY - 1)
+    }
+
+    suspend fun setAllDayReminderTimeMinutes(minutesOfDay: Int) {
+        store.edit { it[ALLDAY_REMINDER_TIME_KEY] = minutesOfDay.coerceIn(0, MINUTES_PER_DAY - 1) }
+    }
+
+    /**
+     * Per-calendar overrides of [defaultReminderMinutes] for **timed** events,
+     * keyed by calendar id. A calendar **present** in the map overrides the global
+     * timed default for its new events: a `null` value means "no reminder", an int
+     * means that lead time. A calendar **absent** from the map inherits the global
+     * default. Serialised as `id=value;id=value`, with `none` for an explicit
+     * no-reminder override. (All-day events ignore this and use
+     * [defaultAllDayReminderMinutes].)
+     */
+    val perCalendarReminderOverride: Flow<Map<Long, Int?>> = store.data.map { prefs ->
+        parseReminderOverrides(prefs[CALENDAR_REMINDER_OVERRIDE_KEY])
+    }
+
+    suspend fun setCalendarReminderOverride(calendarId: Long, override: CalendarReminderOverride) {
+        store.edit { prefs ->
+            val current = parseReminderOverrides(prefs[CALENDAR_REMINDER_OVERRIDE_KEY]).toMutableMap()
+            current.applyOverride(calendarId, override)
+            prefs[CALENDAR_REMINDER_OVERRIDE_KEY] = serializeReminderOverrides(current)
+        }
+    }
+
+    /**
+     * Per-calendar overrides of [defaultAllDayReminderMinutes] for **all-day**
+     * events, with the same semantics as [perCalendarReminderOverride] (absent =
+     * inherit the global all-day default; present null = no reminder).
+     */
+    val perCalendarAllDayReminderOverride: Flow<Map<Long, Int?>> = store.data.map { prefs ->
+        parseReminderOverrides(prefs[CALENDAR_ALLDAY_REMINDER_OVERRIDE_KEY])
+    }
+
+    suspend fun setCalendarAllDayReminderOverride(
+        calendarId: Long,
+        override: CalendarReminderOverride,
+    ) {
+        store.edit { prefs ->
+            val current =
+                parseReminderOverrides(prefs[CALENDAR_ALLDAY_REMINDER_OVERRIDE_KEY]).toMutableMap()
+            current.applyOverride(calendarId, override)
+            prefs[CALENDAR_ALLDAY_REMINDER_OVERRIDE_KEY] = serializeReminderOverrides(current)
+        }
+    }
+
     private fun parseFormFields(stored: String?): Set<EventFormField> = when (stored) {
         null -> DEFAULT_FORM_FIELDS
         else -> stored.split(',')
@@ -143,10 +235,90 @@ class SettingsPrefs @Inject constructor(
         internal val REMINDER_ONBOARDING_KEY = booleanPreferencesKey("reminder_onboarding_done")
         internal val ALLOW_COLOR_UNSUPPORTED_KEY =
             booleanPreferencesKey("allow_color_unsupported_calendars")
+        internal val DEFAULT_REMINDER_KEY = stringPreferencesKey("default_reminder_minutes")
+        internal val DEFAULT_ALLDAY_REMINDER_KEY =
+            stringPreferencesKey("default_allday_reminder_minutes")
+        internal val ALLDAY_REMINDER_TIME_KEY =
+            intPreferencesKey("allday_reminder_time_minutes")
+        /** 09:00 as minutes from midnight; the default all-day reminder fire time. */
+        internal const val DEFAULT_ALLDAY_REMINDER_TIME = 540
+        private const val MINUTES_PER_DAY = 1_440
+        internal val CALENDAR_REMINDER_OVERRIDE_KEY =
+            stringPreferencesKey("per_calendar_reminder_override")
+        internal val CALENDAR_ALLDAY_REMINDER_OVERRIDE_KEY =
+            stringPreferencesKey("per_calendar_allday_reminder_override")
         internal val DEFAULT_FORM_FIELDS =
             setOf(EventFormField.Location, EventFormField.Description)
     }
 }
 
+/** A calendar's reminder-default override (see [SettingsPrefs.perCalendarReminderOverride]). */
+sealed interface CalendarReminderOverride {
+    /** No override — the calendar uses the global default. */
+    data object Inherit : CalendarReminderOverride
+    /** Explicit "no reminder" for this calendar, regardless of the global default. */
+    data object None : CalendarReminderOverride
+    /** A specific lead time in minutes before the event start. */
+    data class Minutes(val minutes: Int) : CalendarReminderOverride
+}
+
+/**
+ * The lead time to prefill on a new event: the matching per-calendar override
+ * if [calendarId] has one for this event kind, otherwise the global default for
+ * that kind. All-day events consult [allDayOverrides] / [allDayGlobal]; timed
+ * events consult [timedOverrides] / [timedGlobal]. `null` = no reminder. Pure so
+ * it can be unit-tested.
+ */
+fun resolveDefaultReminder(
+    timedGlobal: Int?,
+    allDayGlobal: Int?,
+    timedOverrides: Map<Long, Int?>,
+    allDayOverrides: Map<Long, Int?>,
+    calendarId: Long?,
+    isAllDay: Boolean,
+): Int? {
+    val overrides = if (isAllDay) allDayOverrides else timedOverrides
+    val global = if (isAllDay) allDayGlobal else timedGlobal
+    return if (calendarId != null && overrides.containsKey(calendarId)) {
+        overrides[calendarId]
+    } else {
+        global
+    }
+}
+
+/** Apply a [CalendarReminderOverride] to an override map ([Inherit] removes the key). */
+private fun MutableMap<Long, Int?>.applyOverride(
+    calendarId: Long,
+    override: CalendarReminderOverride,
+) {
+    when (override) {
+        CalendarReminderOverride.Inherit -> remove(calendarId)
+        CalendarReminderOverride.None -> put(calendarId, null)
+        is CalendarReminderOverride.Minutes -> put(calendarId, override.minutes)
+    }
+}
+
+private const val NONE = "none"
+private const val ENTRY_SEP = ";"
+private const val KEY_VALUE_SEP = "="
+
+private fun String?.toReminderMinutes(): Int? = when (this) {
+    null, "", NONE -> null
+    else -> toIntOrNull()
+}
+
+private fun parseReminderOverrides(stored: String?): Map<Long, Int?> {
+    if (stored.isNullOrBlank()) return emptyMap()
+    return stored.split(ENTRY_SEP).mapNotNull { entry ->
+        val parts = entry.split(KEY_VALUE_SEP).takeIf { it.size == 2 } ?: return@mapNotNull null
+        val id = parts[0].toLongOrNull() ?: return@mapNotNull null
+        val value = if (parts[1] == NONE) null else parts[1].toIntOrNull() ?: return@mapNotNull null
+        id to value
+    }.toMap()
+}
+
+private fun serializeReminderOverrides(map: Map<Long, Int?>): String =
+    map.entries.joinToString(ENTRY_SEP) { (id, minutes) -> "$id$KEY_VALUE_SEP${minutes ?: NONE}" }
+
 private inline fun <reified E : Enum<E>> String?.toEnum(default: E): E =
     this?.let { stored -> enumValues<E>().firstOrNull { it.name == stored } } ?: default

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/EventDetailIcs.kt

@@ -0,0 +1,29 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import de.jeanlucmakiola.calendula.domain.EventDetail
+
+/**
+ * Build the [IcsEvent] for sharing a single event. We export the event the user
+ * is looking at as a **one-off** VEVENT (no RRULE): the detail screen shows one
+ * occurrence, so "share this event" should hand off exactly that instance, not
+ * a whole series anchored to a possibly-different DTSTART. Reminders are the
+ * already-decoded semantic lead times the detail screen holds.
+ */
+fun EventDetail.toShareIcsEvent(): IcsEvent {
+    val startMillis = instance.start.toEpochMilliseconds()
+    return IcsEvent(
+        uid = deriveIcsUid(existingUid = null, eventId = instance.eventId, dtStartMillis = startMillis),
+        summary = instance.title,
+        start = instance.start,
+        end = instance.end,
+        isAllDay = instance.isAllDay,
+        zoneId = eventTimezone?.takeIf { it.isNotBlank() } ?: "UTC",
+        recurrenceRule = null,
+        location = instance.location,
+        description = description,
+        reminderMinutes = reminders.map { it.minutes },
+        status = status,
+        availability = availability,
+        calendarName = null,
+    )
+}

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsDuration.kt

@@ -0,0 +1,40 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+// Android's calendar provider (and Calendula's own writes) use the non-standard
+// single-unit forms P<n>S / P<n>D / P<n>W — seconds without the RFC-required
+// leading T. Matched first; anything else falls through to the general grammar.
+private val DURATION_SINGLE_UNIT = Regex("""([+-]?)P(\d+)([WDS])""")
+private val DURATION_GENERAL =
+    Regex("""([+-]?)P(?:(\d+)W)?(?:(\d+)D)?(?:T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?)?""")
+
+/**
+ * Milliseconds of a DURATION (`P1D`, `P3600S`, `PT1H30M`, `-PT15M`, `P1W`, …),
+ * sign-aware. Calendula writes `P<days>D` / `P<seconds>S`, but the parser also
+ * accepts the general RFC 5545 grammar so backup `DURATION` rows and foreign
+ * `VALARM` triggers round-trip. Unparseable input is treated as zero.
+ */
+fun parseRfc2445DurationMillis(duration: String?): Long {
+    if (duration.isNullOrBlank()) return 0L
+    val s = duration.trim()
+
+    DURATION_SINGLE_UNIT.matchEntire(s)?.let { m ->
+        val unitSeconds = when (m.groupValues[3]) {
+            "W" -> 7L * 24 * 60 * 60
+            "D" -> 24L * 60 * 60
+            else -> 1L // S
+        }
+        return m.signum() * m.groupValues[2].toLong() * unitSeconds * 1_000L
+    }
+
+    val m = DURATION_GENERAL.matchEntire(s) ?: return 0L
+    val weeks = m.groupValues[2].toLongOrNull() ?: 0L
+    val days = m.groupValues[3].toLongOrNull() ?: 0L
+    val hours = m.groupValues[4].toLongOrNull() ?: 0L
+    val minutes = m.groupValues[5].toLongOrNull() ?: 0L
+    val seconds = m.groupValues[6].toLongOrNull() ?: 0L
+    val totalSeconds = ((((weeks * 7 + days) * 24 + hours) * 60 + minutes) * 60 + seconds)
+    return m.signum() * totalSeconds * 1_000L
+}
+
+/** Sign carried by group 1 (`-` → -1, otherwise +1) of a duration match. */
+private fun MatchResult.signum(): Long = if (groupValues[1] == "-") -1L else 1L

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsEvent.kt

@@ -0,0 +1,43 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import de.jeanlucmakiola.calendula.domain.Availability
+import de.jeanlucmakiola.calendula.domain.EventStatus
+import kotlin.time.Instant
+
+/**
+ * A single event ready to be serialised to a `VEVENT`, decoupled from the
+ * provider so [IcsWriter] stays pure-Kotlin and JVM-testable. [start]/[end] are
+ * absolute instants; [isAllDay] and [recurrenceRule] decide how they are
+ * rendered (see [IcsWriter]'s timezone rule).
+ */
+data class IcsEvent(
+    /** RFC 5545 UID — globally stable across exports (see [deriveIcsUid]). */
+    val uid: String,
+    val summary: String,
+    val start: Instant,
+    /** Exclusive end (for all-day: the next-day midnight, as the provider stores it). */
+    val end: Instant,
+    val isAllDay: Boolean,
+    /** IANA zone id (`Events.EVENT_TIMEZONE`); only used for recurring timed events. */
+    val zoneId: String,
+    /** Bare RRULE value (no `RRULE:` prefix), or null for a one-off event. */
+    val recurrenceRule: String? = null,
+    val location: String? = null,
+    val description: String? = null,
+    /** Reminder lead times in minutes before start (raw provider offsets). */
+    val reminderMinutes: List<Int> = emptyList(),
+    val status: EventStatus = EventStatus.Confirmed,
+    val availability: Availability = Availability.Busy,
+    /** Source calendar name, emitted as `X-CALENDULA-CALENDAR` so a combined backup can fan back out. */
+    val calendarName: String? = null,
+)
+
+/**
+ * The UID to export for a provider event. A row that already carries a UID
+ * (`Events.UID_2445`) keeps it; otherwise we synthesise a **stable** one from
+ * the event id and its DTSTART so the same legacy event yields the same UID
+ * across repeated backups — which keeps a later restore from duplicating it.
+ */
+fun deriveIcsUid(existingUid: String?, eventId: Long, dtStartMillis: Long): String =
+    existingUid?.trim()?.takeIf { it.isNotEmpty() }
+        ?: "$eventId-$dtStartMillis@calendula"

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsParser.kt

@@ -0,0 +1,259 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import de.jeanlucmakiola.calendula.domain.Availability
+import de.jeanlucmakiola.calendula.domain.EventStatus
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.LocalTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.atStartOfDayIn
+import kotlinx.datetime.toInstant
+import kotlin.time.Instant
+
+/**
+ * A `VEVENT` parsed from an `.ics` file — the read-side mirror of [IcsEvent],
+ * but [uid] is nullable (an incoming event may carry none; the insert layer
+ * then assigns one). Times are absolute instants; [isAllDay]/[zoneId] mirror
+ * how the writer encoded them.
+ */
+data class ParsedIcsEvent(
+    val uid: String?,
+    val summary: String,
+    val start: Instant,
+    val end: Instant,
+    val isAllDay: Boolean,
+    val zoneId: String,
+    val recurrenceRule: String? = null,
+    val location: String? = null,
+    val description: String? = null,
+    val reminderMinutes: List<Int> = emptyList(),
+    val status: EventStatus = EventStatus.Confirmed,
+    val availability: Availability = Availability.Busy,
+    val calendarName: String? = null,
+)
+
+/** Things the parser dropped rather than failing — surfaced in the import report. */
+enum class IcsParseWarning {
+    /** A `RECURRENCE-ID` override occurrence (not modelled; only masters import). */
+    ModifiedOccurrenceSkipped,
+
+    /** A `VEVENT` with no parseable `DTSTART`. */
+    EventWithoutStartSkipped,
+
+    /** `ATTENDEE` rows were present; Calendula doesn't import attendees. */
+    AttendeesIgnored,
+
+    /** A `TZID` couldn't be resolved against the device tz database (used local zone). */
+    UnknownTimezone,
+}
+
+data class IcsParseResult(
+    val events: List<ParsedIcsEvent>,
+    val warnings: Set<IcsParseWarning>,
+)
+
+/** Outcome of a bulk `.ics` import into one calendar. */
+data class IcsImportSummary(val imported: Int, val skippedDuplicate: Int)
+
+/**
+ * Hand-rolled RFC 5545 reader, the inverse of [IcsWriter]. Pure and
+ * JVM-testable. Liberal-in/strict-out: unknown properties are ignored, a single
+ * malformed `VEVENT` is skipped (not fatal), and unsupported constructs
+ * (`RECURRENCE-ID`, attendees, unresolved `TZID`) are reported as [warnings]
+ * rather than silently dropped. `VTIMEZONE` blocks are skipped — a `TZID` is
+ * resolved against the OS tz database instead ([deviceZone] is the fallback).
+ */
+class IcsParser(private val deviceZone: TimeZone = TimeZone.currentSystemDefault()) {
+
+    fun parse(text: String): IcsParseResult {
+        val lines = unfoldLines(text)
+        val events = mutableListOf<ParsedIcsEvent>()
+        val warnings = mutableSetOf<IcsParseWarning>()
+        var calendarName: String? = null
+
+        var i = 0
+        while (i < lines.size) {
+            val line = parseContentLine(lines[i])
+            if (line == null) { i++; continue }
+            when {
+                line.isBegin("VEVENT") -> {
+                    val end = indexOfEnd(lines, i + 1, "VEVENT")
+                    parseVevent(lines.subList(i + 1, end), calendarName, warnings)
+                        ?.let(events::add)
+                    i = end + 1
+                }
+                line.isBegin("VTIMEZONE") -> {
+                    // Skipped wholesale; TZIDs resolve against the OS tz database.
+                    i = indexOfEnd(lines, i + 1, "VTIMEZONE") + 1
+                }
+                line.name == "X-WR-CALNAME" -> {
+                    calendarName = unescapeText(line.value).trim().ifEmpty { null }
+                    i++
+                }
+                else -> i++
+            }
+        }
+        return IcsParseResult(events, warnings)
+    }
+
+    private fun parseVevent(
+        body: List<String>,
+        fileCalendarName: String?,
+        warnings: MutableSet<IcsParseWarning>,
+    ): ParsedIcsEvent? {
+        var uid: String? = null
+        var summary = ""
+        var dtStart: IcsDateTime? = null
+        var dtEnd: IcsDateTime? = null
+        var duration: String? = null
+        var rrule: String? = null
+        var location: String? = null
+        var description: String? = null
+        var status = EventStatus.Confirmed
+        var availability = Availability.Busy
+        var calendarName = fileCalendarName
+        val reminders = mutableListOf<Int>()
+        var skipAsOverride = false
+
+        var i = 0
+        while (i < body.size) {
+            val line = parseContentLine(body[i])
+            if (line == null) { i++; continue }
+            when (line.name) {
+                "BEGIN" -> if (line.value.trim().equals("VALARM", true)) {
+                    val end = indexOfEnd(body, i + 1, "VALARM")
+                    parseAlarmMinutes(body.subList(i + 1, end))?.let(reminders::add)
+                    i = end + 1
+                    continue
+                }
+                "UID" -> uid = line.value.trim().ifEmpty { null }
+                "SUMMARY" -> summary = unescapeText(line.value)
+                "DTSTART" -> dtStart = parseIcsDateTime(line, warnings)
+                "DTEND" -> dtEnd = parseIcsDateTime(line, warnings)
+                "DURATION" -> duration = line.value.trim()
+                "RRULE" -> rrule = line.value.trim().ifEmpty { null }
+                "LOCATION" -> location = unescapeText(line.value).ifEmpty { null }
+                "DESCRIPTION" -> description = unescapeText(line.value).ifEmpty { null }
+                "STATUS" -> status = mapIcsStatus(line.value)
+                "TRANSP" -> availability =
+                    if (line.value.trim().equals("TRANSPARENT", true)) Availability.Free
+                    else Availability.Busy
+                "RECURRENCE-ID" -> skipAsOverride = true
+                "ATTENDEE" -> warnings.add(IcsParseWarning.AttendeesIgnored)
+                "X-CALENDULA-CALENDAR" ->
+                    calendarName = unescapeText(line.value).trim().ifEmpty { calendarName }
+            }
+            i++
+        }
+
+        if (skipAsOverride) {
+            warnings.add(IcsParseWarning.ModifiedOccurrenceSkipped)
+            return null
+        }
+        val start = dtStart ?: run {
+            warnings.add(IcsParseWarning.EventWithoutStartSkipped)
+            return null
+        }
+        val end = dtEnd
+            ?: duration?.let {
+                start.copy(
+                    instant = Instant.fromEpochMilliseconds(
+                        start.instant.toEpochMilliseconds() + parseRfc2445DurationMillis(it),
+                    ),
+                )
+            }
+            ?: start
+        return ParsedIcsEvent(
+            uid = uid,
+            summary = summary,
+            start = start.instant,
+            end = end.instant,
+            isAllDay = start.isAllDay,
+            zoneId = start.zoneId,
+            recurrenceRule = rrule,
+            location = location,
+            description = description,
+            reminderMinutes = reminders.distinct(),
+            status = status,
+            availability = availability,
+            calendarName = calendarName,
+        )
+    }
+
+    /** A VALARM's lead time in minutes before start, or null if not a usable relative trigger. */
+    private fun parseAlarmMinutes(body: List<String>): Int? {
+        val trigger = body.asSequence()
+            .mapNotNull { parseContentLine(it) }
+            .firstOrNull { it.name == "TRIGGER" }
+            ?: return null
+        // Absolute (DATE-TIME) triggers can't be expressed as a lead time.
+        if (trigger.params["VALUE"].equals("DATE-TIME", true)) return null
+        val millis = parseRfc2445DurationMillis(trigger.value)
+        // Negative = before start (the normal case) → positive lead minutes.
+        return (-millis / 60_000L).toInt().coerceAtLeast(0)
+    }
+
+    private fun parseIcsDateTime(line: IcsContentLine, warnings: MutableSet<IcsParseWarning>): IcsDateTime? {
+        val raw = line.value.trim()
+        val isDate = line.params["VALUE"].equals("DATE", true) ||
+            (raw.length == 8 && !raw.contains('T'))
+        if (isDate) {
+            val date = parseBasicDate(raw) ?: return null
+            return IcsDateTime(date.atStartOfDayIn(TimeZone.UTC), isAllDay = true, zoneId = "UTC")
+        }
+        val isUtc = raw.endsWith("Z")
+        val ldt = parseBasicDateTime(raw.removeSuffix("Z")) ?: return null
+        if (isUtc) return IcsDateTime(ldt.toInstant(TimeZone.UTC), isAllDay = false, zoneId = "UTC")
+
+        val tzid = line.params["TZID"]
+        val resolved = tzid?.let { id -> runCatching { TimeZone.of(id) }.getOrNull()?.let { id to it } }
+        if (tzid != null && resolved == null) warnings.add(IcsParseWarning.UnknownTimezone)
+        val (zoneId, zone) = resolved ?: (deviceZone.id to deviceZone)
+        return IcsDateTime(ldt.toInstant(zone), isAllDay = false, zoneId = zoneId)
+    }
+
+    private data class IcsDateTime(val instant: Instant, val isAllDay: Boolean, val zoneId: String)
+
+    private companion object {
+        fun IcsContentLine.isBegin(component: String) =
+            name == "BEGIN" && value.trim().equals(component, true)
+
+        /** Index of the matching `END:<component>` at/after [from], or list end. */
+        fun indexOfEnd(lines: List<String>, from: Int, component: String): Int {
+            var i = from
+            while (i < lines.size) {
+                val line = parseContentLine(lines[i])
+                if (line != null && line.name == "END" &&
+                    line.value.trim().equals(component, true)
+                ) {
+                    return i
+                }
+                i++
+            }
+            return lines.size
+        }
+
+        fun mapIcsStatus(value: String): EventStatus = when (value.trim().uppercase()) {
+            "TENTATIVE" -> EventStatus.Tentative
+            "CANCELLED" -> EventStatus.Cancelled
+            else -> EventStatus.Confirmed
+        }
+
+        fun parseBasicDate(s: String): LocalDate? = runCatching {
+            LocalDate(s.substring(0, 4).toInt(), s.substring(4, 6).toInt(), s.substring(6, 8).toInt())
+        }.getOrNull()
+
+        fun parseBasicDateTime(s: String): LocalDateTime? = runCatching {
+            val date = LocalDate(
+                s.substring(0, 4).toInt(), s.substring(4, 6).toInt(), s.substring(6, 8).toInt(),
+            )
+            // Format is YYYYMMDD 'T' HHMMSS; seconds optional.
+            val time = LocalTime(
+                s.substring(9, 11).toInt(),
+                s.substring(11, 13).toInt(),
+                if (s.length >= 15) s.substring(13, 15).toInt() else 0,
+            )
+            LocalDateTime(date, time)
+        }.getOrNull()
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsText.kt

@@ -0,0 +1,155 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+/**
+ * Low-level RFC 5545 text mechanics, kept separate from [IcsWriter] so the
+ * escaping and folding rules can be tested in isolation. Pure Kotlin — no
+ * Android, no time handling.
+ */
+
+/** iCalendar mandates CRLF line breaks, not the platform separator. */
+const val ICS_CRLF: String = "\r\n"
+
+/** RFC 5545 §3.1: content lines SHOULD be folded at 75 octets (excluding the break). */
+private const val MAX_OCTETS = 75
+
+/**
+ * Escape a TEXT value (SUMMARY, DESCRIPTION, LOCATION, …) per RFC 5545 §3.3.11:
+ * backslash, semicolon and comma are escaped, newlines become the literal `\n`.
+ * Backslash is handled first so it doesn't double-escape the others' markers.
+ */
+fun escapeText(value: String): String = buildString(value.length) {
+    for (ch in value) {
+        when (ch) {
+            '\\' -> append("\\\\")
+            ';' -> append("\\;")
+            ',' -> append("\\,")
+            '\n' -> append("\\n")
+            '\r' -> Unit // CR is dropped; a lone CRLF in source text folds to one \n
+            else -> append(ch)
+        }
+    }
+}
+
+/**
+ * Fold a single content line to ≤75 octets per physical line, inserting
+ * `CRLF + space` between segments (the space is part of the 75-octet budget of
+ * the continuation line, so its content caps at 74). Folding counts UTF-8
+ * octets, never splitting a multi-byte character across a boundary.
+ */
+fun foldLine(line: String): String {
+    if (line.toByteArray(Charsets.UTF_8).size <= MAX_OCTETS) return line
+    val out = StringBuilder()
+    var octetsThisLine = 0
+    var first = true
+    var i = 0
+    while (i < line.length) {
+        val cp = line.codePointAt(i)
+        val width = Character.charCount(cp)
+        val piece = line.substring(i, i + width)
+        val pieceOctets = piece.toByteArray(Charsets.UTF_8).size
+        // Continuation lines spend one octet on the leading space.
+        val budget = if (first) MAX_OCTETS else MAX_OCTETS - 1
+        if (octetsThisLine + pieceOctets > budget) {
+            out.append(ICS_CRLF).append(' ')
+            octetsThisLine = 0
+            first = false
+        }
+        out.append(piece)
+        octetsThisLine += pieceOctets
+        i += width
+    }
+    return out.toString()
+}
+
+/**
+ * Reverse of [escapeText]: turn `\n`/`\N` into newlines and unescape `\\`, `\;`,
+ * `\,`. A backslash before any other character is dropped, keeping the
+ * character (lenient — foreign files escape liberally).
+ */
+fun unescapeText(value: String): String = buildString(value.length) {
+    var i = 0
+    while (i < value.length) {
+        val c = value[i]
+        if (c == '\\' && i + 1 < value.length) {
+            when (val next = value[i + 1]) {
+                'n', 'N' -> append('\n')
+                else -> append(next) // \\, \;, \, and any other escaped char
+            }
+            i += 2
+        } else {
+            append(c)
+            i++
+        }
+    }
+}
+
+/**
+ * Reverse of [foldLine] across a whole document: split into physical lines on
+ * CRLF/LF/CR, then re-join any line that begins with a single space or tab onto
+ * the previous one (RFC 5545 unfolding). Returns the logical content lines.
+ */
+fun unfoldLines(text: String): List<String> {
+    val out = mutableListOf<String>()
+    for (physical in text.split("\r\n", "\n", "\r")) {
+        if (physical.isEmpty()) continue
+        val isContinuation = physical[0] == ' ' || physical[0] == '\t'
+        if (isContinuation && out.isNotEmpty()) {
+            out[out.lastIndex] = out.last() + physical.substring(1)
+        } else {
+            out.add(physical)
+        }
+    }
+    return out
+}
+
+/**
+ * One unfolded content line split into its property name, parameters and value:
+ * `SUMMARY;LANGUAGE=en:Lunch` → name `SUMMARY`, params `{LANGUAGE=en}`, value
+ * `Lunch`. The value is everything after the first colon that isn't inside a
+ * quoted parameter; param keys are upper-cased, quoted param values unquoted.
+ * Returns null for a line with no colon.
+ */
+data class IcsContentLine(val name: String, val params: Map<String, String>, val value: String)
+
+fun parseContentLine(line: String): IcsContentLine? {
+    var inQuote = false
+    var colon = -1
+    for (i in line.indices) {
+        when (line[i]) {
+            '"' -> inQuote = !inQuote
+            ':' -> if (!inQuote) { colon = i; break }
+        }
+    }
+    if (colon < 0) return null
+    val head = splitUnquoted(line.substring(0, colon), ';')
+    val name = head.firstOrNull()?.trim()?.uppercase().orEmpty()
+    if (name.isEmpty()) return null
+    val params = buildMap {
+        for (part in head.drop(1)) {
+            val eq = part.indexOf('=')
+            if (eq > 0) {
+                put(
+                    part.substring(0, eq).trim().uppercase(),
+                    part.substring(eq + 1).trim().removeSurrounding("\""),
+                )
+            }
+        }
+    }
+    return IcsContentLine(name, params, line.substring(colon + 1))
+}
+
+/** Split on [delimiter] except where it falls inside a double-quoted run. */
+private fun splitUnquoted(text: String, delimiter: Char): List<String> {
+    val parts = mutableListOf<String>()
+    val current = StringBuilder()
+    var inQuote = false
+    for (c in text) {
+        when {
+            c == '"' -> { inQuote = !inQuote; current.append(c) }
+            c == delimiter && !inQuote -> { parts.add(current.toString()); current.clear() }
+            else -> current.append(c)
+        }
+    }
+    parts.add(current.toString())
+    return parts
+}

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsWriter.kt

@@ -0,0 +1,124 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import de.jeanlucmakiola.calendula.domain.Availability
+import de.jeanlucmakiola.calendula.domain.EventStatus
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.number
+import kotlinx.datetime.toLocalDateTime
+import kotlin.time.Instant
+
+/** Default `PRODID` advertising the writer that produced the file. */
+const val ICS_PROD_ID: String = "-//Jean-Luc Makiola//Calendula//EN"
+
+/**
+ * Hand-rolled RFC 5545 serialiser for the subset Calendula models. No iCal
+ * library: we stay on `kotlinx-datetime` and own the output, exactly as
+ * `domain/Recurrence.kt` owns RRULE. Pure and JVM-testable — the caller
+ * supplies [dtStamp] (the export moment) so the writer never reads a clock.
+ *
+ * Timezone rule (see plan 05, decision 1):
+ *  - all-day      → `VALUE=DATE`, no zone;
+ *  - timed one-off → UTC instant with a `Z` suffix (an instant is an instant);
+ *  - timed recurring → `TZID`-labelled local wall time, so the series stays
+ *    anchored to wall-clock across DST. No `VTIMEZONE` block is emitted; import
+ *    resolves the `TZID` against the OS tz database.
+ */
+class IcsWriter(private val prodId: String = ICS_PROD_ID) {
+
+    fun writeCalendar(events: List<IcsEvent>, dtStamp: Instant): String {
+        val lines = buildList {
+            add("BEGIN:VCALENDAR")
+            add("VERSION:2.0")
+            add("PRODID:$prodId")
+            add("CALSCALE:GREGORIAN")
+            events.forEach { appendEvent(it, dtStamp) }
+            add("END:VCALENDAR")
+        }
+        return lines.joinToString(ICS_CRLF, postfix = ICS_CRLF) { foldLine(it) }
+    }
+
+    private fun MutableList<String>.appendEvent(event: IcsEvent, dtStamp: Instant) {
+        add("BEGIN:VEVENT")
+        add("UID:${event.uid}")
+        add("DTSTAMP:${utcStamp(dtStamp)}")
+        add("SUMMARY:${escapeText(event.summary)}")
+        appendTimes(event)
+        event.recurrenceRule?.takeIf { it.isNotBlank() }
+            ?.let { add("RRULE:${it.removePrefix("RRULE:")}") }
+        event.location?.takeIf { it.isNotBlank() }
+            ?.let { add("LOCATION:${escapeText(it)}") }
+        event.description?.takeIf { it.isNotBlank() }
+            ?.let { add("DESCRIPTION:${escapeText(it)}") }
+        add("STATUS:${statusValue(event.status)}")
+        add("TRANSP:${transpValue(event.availability)}")
+        event.calendarName?.takeIf { it.isNotBlank() }
+            ?.let { add("X-CALENDULA-CALENDAR:${escapeText(it)}") }
+        event.reminderMinutes.filter { it >= 0 }.distinct().forEach { minutes ->
+            appendAlarm(minutes, event.summary)
+        }
+        add("END:VEVENT")
+    }
+
+    private fun MutableList<String>.appendTimes(event: IcsEvent) = when {
+        event.isAllDay -> {
+            add("DTSTART;VALUE=DATE:${utcDate(event.start)}")
+            add("DTEND;VALUE=DATE:${utcDate(event.end)}")
+        }
+        // Recurring: anchor to wall-clock in the event's own zone.
+        event.recurrenceRule?.isNotBlank() == true -> {
+            val zone = runCatching { TimeZone.of(event.zoneId) }.getOrNull()
+            if (zone != null) {
+                add("DTSTART;TZID=${event.zoneId}:${localStamp(event.start, zone)}")
+                add("DTEND;TZID=${event.zoneId}:${localStamp(event.end, zone)}")
+            } else {
+                // Unknown zone id → fall back to plain UTC instants.
+                add("DTSTART:${utcStamp(event.start)}")
+                add("DTEND:${utcStamp(event.end)}")
+            }
+        }
+        else -> {
+            add("DTSTART:${utcStamp(event.start)}")
+            add("DTEND:${utcStamp(event.end)}")
+        }
+    }
+
+    private fun MutableList<String>.appendAlarm(minutes: Int, summary: String) {
+        add("BEGIN:VALARM")
+        add("ACTION:DISPLAY")
+        add("DESCRIPTION:${escapeText(summary.ifBlank { "Reminder" })}")
+        add("TRIGGER:${triggerValue(minutes)}")
+        add("END:VALARM")
+    }
+
+    private companion object {
+        fun statusValue(status: EventStatus): String = when (status) {
+            EventStatus.Confirmed -> "CONFIRMED"
+            EventStatus.Tentative -> "TENTATIVE"
+            EventStatus.Cancelled -> "CANCELLED"
+        }
+
+        // iCal TRANSP is binary; only an explicitly free event is TRANSPARENT.
+        fun transpValue(availability: Availability): String =
+            if (availability == Availability.Free) "TRANSPARENT" else "OPAQUE"
+
+        // A lead time of 0 fires at start (PT0M); anything positive is "before".
+        fun triggerValue(minutes: Int): String =
+            if (minutes <= 0) "PT0M" else "-PT${minutes}M"
+
+        fun utcStamp(instant: Instant): String =
+            basic(instant.toLocalDateTime(TimeZone.UTC)) + "Z"
+
+        fun localStamp(instant: Instant, zone: TimeZone): String =
+            basic(instant.toLocalDateTime(zone))
+
+        fun utcDate(instant: Instant): String {
+            val dt = instant.toLocalDateTime(TimeZone.UTC)
+            return "%04d%02d%02d".format(dt.year, dt.month.number, dt.day)
+        }
+
+        fun basic(dt: LocalDateTime): String = "%04d%02d%02dT%02d%02d%02d".format(
+            dt.year, dt.month.number, dt.day, dt.hour, dt.minute, dt.second,
+        )
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/ParsedIcsForm.kt

@@ -0,0 +1,38 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import de.jeanlucmakiola.calendula.domain.EventForm
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.LocalTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.toLocalDateTime
+
+/**
+ * Prefill the create form from a single parsed `.ics` event (the "open one
+ * event" path). [calendarId] is left null so the form preselects the last-used
+ * calendar, exactly like a fresh create — the user confirms the target and
+ * reviews everything before saving. Mirrors `EventDetail.toEditForm`'s all-day
+ * handling (provider all-day times are UTC midnights with an exclusive end).
+ */
+fun ParsedIcsEvent.toEventForm(zone: TimeZone): EventForm {
+    val (start, end) = if (isAllDay) {
+        val startDate = this.start.toLocalDateTime(TimeZone.UTC).date
+        val endExclusive = this.end.toLocalDateTime(TimeZone.UTC).date
+        val endDate = maxOf(startDate, LocalDate.fromEpochDays(endExclusive.toEpochDays() - 1))
+        LocalDateTime(startDate, LocalTime(9, 0)) to LocalDateTime(endDate, LocalTime(10, 0))
+    } else {
+        this.start.toLocalDateTime(zone) to this.end.toLocalDateTime(zone)
+    }
+    return EventForm(
+        calendarId = null,
+        title = summary,
+        isAllDay = isAllDay,
+        start = start,
+        end = end,
+        location = location.orEmpty(),
+        description = description.orEmpty(),
+        reminders = reminderMinutes.distinct().sorted(),
+        availability = availability,
+        rrule = recurrenceRule?.removePrefix("RRULE:")?.takeIf { it.isNotBlank() },
+    )
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/CalendarHost.kt

@@ -15,6 +15,7 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
+import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.ui.agenda.AgendaScreen
 import de.jeanlucmakiola.calendula.ui.calendars.CalendarsScreen
@@ -23,6 +24,7 @@ import de.jeanlucmakiola.calendula.ui.common.rememberCalendarSlideSpec
 import de.jeanlucmakiola.calendula.ui.day.DayScreen
 import de.jeanlucmakiola.calendula.ui.detail.EventDetailScreen
 import de.jeanlucmakiola.calendula.ui.edit.EventEditScreen
+import de.jeanlucmakiola.calendula.ui.imports.ImportScreen
 import de.jeanlucmakiola.calendula.ui.month.MonthScreen
 import de.jeanlucmakiola.calendula.ui.settings.SettingsScreen
 import de.jeanlucmakiola.calendula.ui.week.WeekScreen
@@ -48,6 +50,8 @@ fun CalendarHost(
     onDetailKeyConsumed: () -> Unit = {},
     widgetNavRequest: WidgetNavRequest? = null,
     onWidgetNavConsumed: () -> Unit = {},
+    requestedImportUri: android.net.Uri? = null,
+    onImportConsumed: () -> Unit = {},
 ) {
     var view by rememberSaveable { mutableStateOf(CalendarView.Week) }
     val onSelectView: (CalendarView) -> Unit = { view = it }
@@ -121,6 +125,18 @@ fun CalendarHost(
     var editKey by rememberSaveable { mutableStateOf<LongArray?>(null) }
     var heldEditKey by remember { mutableStateOf<LongArray?>(null) }
 
+    // An opened/received .ics file. [ImportScreen] parses it and either opens
+    // the prefilled create form (one event → [importForm]) or its own bulk
+    // picker (many). A plain conditional overlay (no slide) — it's transient.
+    var importUri by remember { mutableStateOf<android.net.Uri?>(null) }
+    var importForm by remember { mutableStateOf<EventForm?>(null) }
+    LaunchedEffect(requestedImportUri) {
+        if (requestedImportUri != null) {
+            importUri = requestedImportUri
+            onImportConsumed()
+        }
+    }
+
     // A home-screen widget launch asks to open a date (→ day view) or start a
     // create. Handled once and cleared, mirroring [requestedDetailKey].
     LaunchedEffect(widgetNavRequest) {
@@ -254,5 +270,26 @@ fun CalendarHost(
         ) {
             CalendarsScreen(onBack = { showCalendars = false })
         }
+
+        // Import flow for an opened/received .ics file. A single event routes
+        // into the create form (prefilled, for review); many open the picker.
+        importUri?.let { uri ->
+            ImportScreen(
+                uri = uri,
+                onClose = { importUri = null },
+                onOpenSingle = { form ->
+                    importUri = null
+                    importForm = form
+                },
+            )
+        }
+        importForm?.let { form ->
+            EventEditScreen(
+                initialDateIso = null,
+                initialForm = form,
+                onClose = { importForm = null },
+                onSaved = { importForm = null },
+            )
+        }
     }
 }

app/src/main/java/de/jeanlucmakiola/calendula/ui/RootScreen.kt

@@ -27,6 +27,8 @@ fun RootScreen(
     onDetailKeyConsumed: () -> Unit = {},
     widgetNavRequest: WidgetNavRequest? = null,
     onWidgetNavConsumed: () -> Unit = {},
+    requestedImportUri: android.net.Uri? = null,
+    onImportConsumed: () -> Unit = {},
 ) {
     val context = LocalContext.current
     var hasPermission by remember {
@@ -62,6 +64,8 @@ fun RootScreen(
                 onDetailKeyConsumed = onDetailKeyConsumed,
                 widgetNavRequest = widgetNavRequest,
                 onWidgetNavConsumed = onWidgetNavConsumed,
+                requestedImportUri = requestedImportUri,
+                onImportConsumed = onImportConsumed,
             )
             false -> ReminderOnboardingScreen(
                 onFinished = reminderOnboarding::finish,

app/src/main/java/de/jeanlucmakiola/calendula/ui/calendars/CalendarsScreen.kt

@@ -5,6 +5,8 @@ import android.content.Context
 import android.content.Intent
 import android.provider.Settings
 import androidx.activity.compose.BackHandler
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.foundation.background
 import androidx.compose.foundation.isSystemInDarkTheme
 import androidx.compose.foundation.layout.Arrangement
@@ -30,6 +32,7 @@ import androidx.compose.material.icons.filled.CalendarMonth
 import androidx.compose.material.icons.filled.Close
 import androidx.compose.material.icons.filled.Delete
 import androidx.compose.material.icons.filled.Edit
+import androidx.compose.material.icons.filled.FileDownload
 import androidx.compose.material.icons.filled.OpenInNew
 import androidx.compose.material.icons.filled.Palette
 import androidx.compose.material3.AlertDialog
@@ -77,6 +80,7 @@ import de.jeanlucmakiola.calendula.ui.common.InlineTextField
 import de.jeanlucmakiola.calendula.ui.common.Position
 import de.jeanlucmakiola.calendula.ui.common.pastelize
 import de.jeanlucmakiola.calendula.ui.common.positionOf
+import java.time.LocalDate
 
 /** Sentinel [editorId] meaning "the editor is composing a new calendar". */
 private const val NEW_CALENDAR_ID = Long.MIN_VALUE
@@ -95,6 +99,7 @@ fun CalendarsScreen(
 ) {
     val calendars by viewModel.calendars.collectAsStateWithLifecycle()
     val error by viewModel.error.collectAsStateWithLifecycle()
+    val backupResult by viewModel.backupResult.collectAsStateWithLifecycle()
 
     // null = list; NEW_CALENDAR_ID = create; any other id = edit that calendar.
     // [editorSession] bumps on every open so the editor's field state resets for
@@ -131,6 +136,9 @@ fun CalendarsScreen(
             synced = calendars.filterNot { it.isLocal },
             error = error,
             onConsumeError = viewModel::consumeError,
+            backupResult = backupResult,
+            onExportBackup = viewModel::exportBackup,
+            onConsumeBackupResult = viewModel::consumeBackupResult,
             onBack = onBack,
             onAdd = { editorSession++; editorId = NEW_CALENDAR_ID },
             onEdit = { calendar -> editorSession++; editorId = calendar.id },
@@ -144,6 +152,9 @@ private fun CalendarsList(
     synced: List<CalendarSource>,
     error: Boolean,
     onConsumeError: () -> Unit,
+    backupResult: BackupResult?,
+    onExportBackup: (android.net.Uri) -> Unit,
+    onConsumeBackupResult: () -> Unit,
     onBack: () -> Unit,
     onAdd: () -> Unit,
     onEdit: (CalendarSource) -> Unit,
@@ -159,6 +170,31 @@ private fun CalendarsList(
         }
     }
 
+    // SAF "create document" target for the backup file. The picked Uri is handed
+    // to the VM to stream the .ics into.
+    val createBackup = rememberLauncherForActivityResult(
+        contract = ActivityResultContracts.CreateDocument("text/calendar"),
+    ) { uri -> uri?.let(onExportBackup) }
+
+    val backupFailedText = stringResource(R.string.calendars_backup_failed)
+    LaunchedEffect(backupResult) {
+        when (val r = backupResult) {
+            is BackupResult.Success -> {
+                snackbarHostState.showSnackbar(
+                    context.resources.getQuantityString(
+                        R.plurals.calendars_backup_done, r.eventCount, r.eventCount,
+                    ),
+                )
+                onConsumeBackupResult()
+            }
+            BackupResult.Failure -> {
+                snackbarHostState.showSnackbar(backupFailedText)
+                onConsumeBackupResult()
+            }
+            null -> Unit
+        }
+    }
+
     CollapsingScaffold(
         title = stringResource(R.string.calendars_title),
         onBack = onBack,
@@ -195,6 +231,22 @@ private fun CalendarsList(
             onClick = onAdd,
         )
 
+        // Backup — local calendars have no sync, so a .ics export is their only
+        // safety net. Offered only when there is something to back up.
+        if (local.isNotEmpty()) {
+            Spacer(Modifier.height(16.dp))
+            SectionHeader(stringResource(R.string.calendars_backup_header))
+            HintText(stringResource(R.string.calendars_backup_hint))
+            GroupedRow(
+                title = stringResource(R.string.calendars_backup_action),
+                position = Position.Alone,
+                leading = { LeadingAvatar(Icons.Default.FileDownload) },
+                onClick = {
+                    runCatching { createBackup.launch("calendula-backup-${LocalDate.now()}.ics") }
+                },
+            )
+        }
+
         Spacer(Modifier.height(16.dp))
 
         // Synced calendars — read-only, grouped by account, each with a
@@ -429,6 +481,25 @@ private fun AccountHeader(account: String, accountType: String) {
     }
 }
 
+/** Neutral circular chip carrying an arbitrary icon — matches [AddAvatar]'s shape. */
+@Composable
+private fun LeadingAvatar(icon: ImageVector) {
+    Box(
+        modifier = Modifier
+            .size(40.dp)
+            .clip(CircleShape)
+            .background(MaterialTheme.colorScheme.surfaceContainerHighest),
+        contentAlignment = Alignment.Center,
+    ) {
+        Icon(
+            icon,
+            contentDescription = null,
+            tint = MaterialTheme.colorScheme.onSurfaceVariant,
+            modifier = Modifier.size(22.dp),
+        )
+    }
+}
+
 /** Neutral circular chip with a "+" — the leading icon for add-actions. */
 @Composable
 private fun AddAvatar() {

app/src/main/java/de/jeanlucmakiola/calendula/ui/calendars/CalendarsViewModel.kt

@@ -1,11 +1,14 @@
 package de.jeanlucmakiola.calendula.ui.calendars
 
+import android.net.Uri
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
 import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
 import de.jeanlucmakiola.calendula.data.di.IoDispatcher
+import de.jeanlucmakiola.calendula.data.ics.IcsExporter
 import de.jeanlucmakiola.calendula.domain.CalendarSource
+import de.jeanlucmakiola.calendula.domain.ics.IcsWriter
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
@@ -15,7 +18,9 @@ import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
 import kotlin.coroutines.cancellation.CancellationException
+import kotlin.time.Clock
 import javax.inject.Inject
 
 /**
@@ -27,6 +32,7 @@ import javax.inject.Inject
 @HiltViewModel
 class CalendarsViewModel @Inject constructor(
     private val repository: CalendarRepository,
+    private val icsExporter: IcsExporter,
     @IoDispatcher private val io: CoroutineDispatcher,
 ) : ViewModel() {
 
@@ -45,6 +51,36 @@ class CalendarsViewModel @Inject constructor(
 
     fun consumeError() { _error.value = false }
 
+    private val _backupResult = MutableStateFlow<BackupResult?>(null)
+    val backupResult: StateFlow<BackupResult?> = _backupResult.asStateFlow()
+
+    fun consumeBackupResult() { _backupResult.value = null }
+
+    /**
+     * Serialise every event of the writable local calendars into the chosen SAF
+     * document [uri] as one `VCALENDAR`. Result (event count, or failure) lands
+     * in [backupResult] for a one-shot message.
+     */
+    fun exportBackup(uri: Uri) {
+        viewModelScope.launch {
+            _backupResult.value = try {
+                val count = withContext(io) {
+                    val events = repository.exportEvents()
+                    icsExporter.writeDocument(
+                        uri = uri,
+                        content = IcsWriter().writeCalendar(events, Clock.System.now()),
+                    )
+                    events.size
+                }
+                BackupResult.Success(count)
+            } catch (e: CancellationException) {
+                throw e
+            } catch (e: Exception) {
+                BackupResult.Failure
+            }
+        }
+    }
+
     fun createCalendar(displayName: String, color: Int, description: String?) = write {
         repository.createLocalCalendar(displayName, color, description)
     }
@@ -69,3 +105,9 @@ class CalendarsViewModel @Inject constructor(
         }
     }
 }
+
+/** Outcome of a whole-calendar backup, surfaced once to the screen. */
+sealed interface BackupResult {
+    data class Success(val eventCount: Int) : BackupResult
+    data object Failure : BackupResult
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/DialogControls.kt

@@ -0,0 +1,94 @@
+package de.jeanlucmakiola.calendula.ui.common
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.ArrowDropDown
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.input.KeyboardType
+import androidx.compose.ui.unit.dp
+
+/**
+ * Tonal 3-digit number input shared by the custom reminder/recurrence steps and
+ * the reminder pickers — the app's [InlineTextField] over a tonal surface, so it
+ * matches the card/grouped-row design language (not Material's outlined field).
+ */
+@Composable
+fun DialogAmountField(
+    value: String,
+    onValueChange: (String) -> Unit,
+    placeholder: String,
+) {
+    // surfaceContainerHighest — the picker/dialog sits on surfaceContainerHigh,
+    // so anything lower vanishes.
+    Surface(
+        color = MaterialTheme.colorScheme.surfaceContainerHighest,
+        shape = RoundedCornerShape(12.dp),
+    ) {
+        InlineTextField(
+            value = value,
+            onValueChange = { text ->
+                if (text.length <= 3 && text.all(Char::isDigit)) onValueChange(text)
+            },
+            placeholder = placeholder,
+            textStyle = MaterialTheme.typography.titleMedium,
+            keyboardType = KeyboardType.Number,
+            modifier = Modifier
+                .width(72.dp)
+                .padding(horizontal = 14.dp, vertical = 12.dp),
+        )
+    }
+}
+
+/** Tonal dropdown trigger + menu shared by the custom reminder/recurrence steps and pickers. */
+@Composable
+fun DialogUnitDropdown(
+    label: String,
+    entries: List<String>,
+    onPick: (Int) -> Unit,
+) {
+    var open by remember { mutableStateOf(false) }
+    Box {
+        Surface(
+            color = MaterialTheme.colorScheme.surfaceContainerHighest,
+            shape = RoundedCornerShape(12.dp),
+            onClick = { open = true },
+        ) {
+            Row(
+                verticalAlignment = Alignment.CenterVertically,
+                modifier = Modifier.padding(start = 14.dp, end = 8.dp, top = 12.dp, bottom = 12.dp),
+            ) {
+                Text(text = label, style = MaterialTheme.typography.titleMedium)
+                Spacer(Modifier.width(4.dp))
+                Icon(imageVector = Icons.Default.ArrowDropDown, contentDescription = null)
+            }
+        }
+        DropdownMenu(expanded = open, onDismissRequest = { open = false }) {
+            entries.forEachIndexed { index, entry ->
+                DropdownMenuItem(
+                    text = { Text(entry) },
+                    onClick = {
+                        onPick(index)
+                        open = false
+                    },
+                )
+            }
+        }
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/GroupedList.kt

@@ -10,7 +10,9 @@ import androidx.compose.foundation.layout.ColumnScope
 import androidx.compose.foundation.layout.RowScope
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.consumeWindowInsets
 import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.imePadding
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.shape.RoundedCornerShape
@@ -102,7 +104,19 @@ fun CollapsingScaffold(
         Column(
             modifier = Modifier
                 .padding(innerPadding)
+                // Mark the scaffold's system-bar insets as consumed so the
+                // imePadding below adds only the keyboard height beyond them
+                // (max, not sum) — otherwise the nav-bar inset double-counts and
+                // leaves an empty strip above the keyboard.
+                .consumeWindowInsets(innerPadding)
                 .fillMaxSize()
+                // Paint the surface across the full area before imePadding carves
+                // into it, so any sliver above the keyboard reads as surface — not
+                // the dialog window's black — during the IME animation.
+                .background(MaterialTheme.colorScheme.surface)
+                // Shrink the scroll viewport by the keyboard inset so a focused
+                // field (e.g. the custom-reminder amount) can scroll into view.
+                .imePadding()
                 .verticalScroll(rememberScrollState())
                 .padding(top = 8.dp, bottom = 24.dp),
             content = content,

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/Picker.kt

@@ -0,0 +1,282 @@
+package de.jeanlucmakiola.calendula.ui.common
+
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ColumnScope
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Check
+import androidx.compose.material3.FilledTonalButton
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.SegmentedButton
+import androidx.compose.material3.SegmentedButtonDefaults
+import androidx.compose.material3.SingleChoiceSegmentedButtonRow
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import android.view.WindowManager
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.SideEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalView
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.window.Dialog
+import androidx.compose.ui.window.DialogProperties
+import androidx.compose.ui.window.DialogWindowProvider
+import de.jeanlucmakiola.calendula.R
+import de.jeanlucmakiola.calendula.data.prefs.CalendarReminderOverride
+
+/**
+ * Shared full-screen scaffold for selection pickers: a full-bleed [Dialog] that
+ * reuses the app's [CollapsingScaffold] (collapsing title + back button), so a
+ * picker is visually identical to a Settings sub-page and uses the full width.
+ * [content] places the connected grouped rows; selecting one calls [onDismiss].
+ */
+@Composable
+fun FullScreenPicker(
+    title: String,
+    onDismiss: () -> Unit,
+    content: @Composable ColumnScope.() -> Unit,
+) {
+    Dialog(
+        onDismissRequest = onDismiss,
+        properties = DialogProperties(
+            usePlatformDefaultWidth = false,
+            decorFitsSystemWindows = false,
+        ),
+    ) {
+        // The dialog window pans by default when the keyboard opens, which —
+        // combined with the content's own imePadding — leaves a fixed black gap
+        // above the keyboard. Switch it to ADJUST_NOTHING so the window stays
+        // full-screen and imePadding alone lifts the focused field.
+        val view = LocalView.current
+        SideEffect {
+            (view.parent as? DialogWindowProvider)?.window
+                ?.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_NOTHING)
+        }
+        CollapsingScaffold(title = title, onBack = onDismiss, content = content)
+    }
+}
+
+/**
+ * General single-select picker, full-screen: each option is a connected grouped
+ * row and the current one carries a check. Drop-in for the former dialog
+ * (theme, week start, language, …).
+ */
+@Composable
+fun <T> OptionPicker(
+    title: String,
+    options: List<T>,
+    selected: T,
+    label: @Composable (T) -> String,
+    onSelect: (T) -> Unit,
+    onDismiss: () -> Unit,
+) {
+    FullScreenPicker(title = title, onDismiss = onDismiss) {
+        options.forEachIndexed { index, option ->
+            val isSelected = option == selected
+            GroupedRow(
+                title = label(option),
+                position = positionOf(index, options.size),
+                selected = isSelected,
+                trailing = if (isSelected) {
+                    { SelectedCheck() }
+                } else {
+                    null
+                },
+                onClick = {
+                    onSelect(option)
+                    onDismiss()
+                },
+            )
+        }
+    }
+}
+
+/**
+ * Reminder-default picker, full-screen: the grouped list (with an optional "Use
+ * default reminder" row and a "None" row), the [presets] as lead-time rows, and
+ * a "Custom" row that expands an inline number field plus a segmented unit
+ * selector. Returns the choice as a [CalendarReminderOverride].
+ */
+@Composable
+fun ReminderDefaultPicker(
+    title: String,
+    presets: List<Int>,
+    selected: CalendarReminderOverride,
+    allowInherit: Boolean,
+    onSelect: (CalendarReminderOverride) -> Unit,
+    onDismiss: () -> Unit,
+) {
+    val selectedMinutes = (selected as? CalendarReminderOverride.Minutes)?.minutes
+    val customSelected = selectedMinutes != null && selectedMinutes !in presets
+    val seed = decomposeReminder(selectedMinutes?.takeIf { customSelected })
+
+    var customExpanded by rememberSaveable { mutableStateOf(false) }
+    var amountText by rememberSaveable { mutableStateOf(seed.first) }
+    var unit by rememberSaveable { mutableStateOf(seed.second) }
+
+    val options = buildList {
+        if (allowInherit) add(CalendarReminderOverride.Inherit)
+        add(CalendarReminderOverride.None)
+        presets.forEach { add(CalendarReminderOverride.Minutes(it)) }
+    }
+    val rowCount = options.size + 1 // + the custom row
+
+    FullScreenPicker(title = title, onDismiss = onDismiss) {
+        options.forEachIndexed { index, option ->
+            val isSelected = option == selected
+            GroupedRow(
+                title = reminderOverrideLabel(option),
+                position = positionOf(index, rowCount),
+                selected = isSelected,
+                trailing = if (isSelected) {
+                    { SelectedCheck() }
+                } else {
+                    null
+                },
+                onClick = {
+                    onSelect(option)
+                    onDismiss()
+                },
+            )
+        }
+        // When expanded, the Custom row connects downward into the editor card
+        // so the two read as one grouped container (the per-calendar pattern).
+        GroupedRow(
+            title = if (customSelected) {
+                stringResource(
+                    R.string.reminder_custom_with_value,
+                    reminderLeadTimeLabel(selectedMinutes!!),
+                )
+            } else {
+                stringResource(R.string.event_edit_reminder_custom)
+            },
+            position = if (customExpanded) Position.Top else positionOf(options.size, rowCount),
+            selected = customSelected,
+            trailing = if (customSelected) {
+                { SelectedCheck() }
+            } else {
+                null
+            },
+            onClick = { customExpanded = !customExpanded },
+        )
+        AnimatedVisibility(visible = customExpanded) {
+            CustomReminderEditor(
+                amountText = amountText,
+                onAmountChange = { amountText = it },
+                unit = unit,
+                onUnitChange = { unit = it },
+                onConfirm = { minutes ->
+                    onSelect(CalendarReminderOverride.Minutes(minutes))
+                    onDismiss()
+                },
+            )
+        }
+    }
+}
+
+/**
+ * The expanded "Custom" lead-time editor: a tonal card connected to the Custom
+ * row above it (matching the grouped-row system, so the two read as one
+ * container). An amount field with a live preview of the resulting lead time, a
+ * single-choice unit toggle, and a tonal confirm enabled only for a valid
+ * 1–999 amount. [onConfirm] receives the final lead time in minutes.
+ */
+@Composable
+private fun CustomReminderEditor(
+    amountText: String,
+    onAmountChange: (String) -> Unit,
+    unit: ReminderUnit,
+    onUnitChange: (ReminderUnit) -> Unit,
+    onConfirm: (Int) -> Unit,
+) {
+    val amount = amountText.toIntOrNull()?.takeIf { it in 1..999 }
+    Surface(
+        color = MaterialTheme.colorScheme.surfaceContainerHigh,
+        // A Position.Bottom shape: tight top corners meeting the row, full bottom.
+        shape = RoundedCornerShape(topStart = 6.dp, topEnd = 6.dp, bottomStart = 22.dp, bottomEnd = 22.dp),
+        modifier = Modifier
+            .fillMaxWidth()
+            .padding(horizontal = 16.dp),
+    ) {
+        Column(
+            modifier = Modifier.padding(16.dp),
+            verticalArrangement = Arrangement.spacedBy(16.dp),
+        ) {
+            // Unit toggle first so it stays visible above the keyboard once the
+            // amount field (the bottom row) is focused and scrolled into view.
+            SingleChoiceSegmentedButtonRow(modifier = Modifier.fillMaxWidth()) {
+                ReminderUnit.entries.forEachIndexed { index, entry ->
+                    SegmentedButton(
+                        selected = unit == entry,
+                        onClick = { onUnitChange(entry) },
+                        shape = SegmentedButtonDefaults.itemShape(index, ReminderUnit.entries.size),
+                        label = { Text(stringResource(reminderUnitLabel(entry))) },
+                    )
+                }
+            }
+            // Amount, a live preview of the lead time it resolves to, and Set —
+            // all on one row, sitting just above the keyboard.
+            Row(verticalAlignment = Alignment.CenterVertically) {
+                DialogAmountField(
+                    value = amountText,
+                    onValueChange = onAmountChange,
+                    placeholder = "10",
+                )
+                Spacer(Modifier.width(16.dp))
+                Text(
+                    text = amount?.let { reminderLeadTimeLabel(it * unit.minutesFactor) }
+                        ?: stringResource(R.string.reminder_custom_amount),
+                    style = MaterialTheme.typography.bodyLarge,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    modifier = Modifier.weight(1f),
+                )
+                Spacer(Modifier.width(16.dp))
+                FilledTonalButton(
+                    onClick = { amount?.let { onConfirm(it * unit.minutesFactor) } },
+                    enabled = amount != null,
+                ) {
+                    Text(stringResource(R.string.reminder_custom_set))
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun SelectedCheck() {
+    Icon(
+        imageVector = Icons.Default.Check,
+        contentDescription = null,
+        tint = MaterialTheme.colorScheme.primary,
+    )
+}
+
+@Composable
+private fun reminderOverrideLabel(override: CalendarReminderOverride): String = when (override) {
+    CalendarReminderOverride.Inherit -> stringResource(R.string.reminder_use_default)
+    CalendarReminderOverride.None -> stringResource(R.string.reminder_none)
+    is CalendarReminderOverride.Minutes -> reminderLeadTimeLabel(override.minutes)
+}
+
+/** Seed the custom editor: the largest exact unit for [minutes] (null → empty). */
+private fun decomposeReminder(minutes: Int?): Pair<String, ReminderUnit> = when {
+    minutes == null -> "" to ReminderUnit.Minutes
+    minutes % 10_080 == 0 -> (minutes / 10_080).toString() to ReminderUnit.Weeks
+    minutes % 1_440 == 0 -> (minutes / 1_440).toString() to ReminderUnit.Days
+    minutes % 60 == 0 -> (minutes / 60).toString() to ReminderUnit.Hours
+    else -> minutes.toString() to ReminderUnit.Minutes
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/ReminderFormatting.kt

@@ -0,0 +1,46 @@
+package de.jeanlucmakiola.calendula.ui.common
+
+import androidx.annotation.StringRes
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.pluralStringResource
+import androidx.compose.ui.res.stringResource
+import de.jeanlucmakiola.calendula.R
+
+/** Common reminder lead times offered as quick picks in the form and settings. */
+val REMINDER_PRESETS = listOf(0, 10, 30, 60, 1_440)
+
+/** The unit of a custom reminder lead time; [minutesFactor] converts to minutes. */
+enum class ReminderUnit(val minutesFactor: Int) {
+    Minutes(1),
+    Hours(60),
+    Days(1_440),
+    Weeks(10_080),
+}
+
+@StringRes
+fun reminderUnitLabel(unit: ReminderUnit): Int = when (unit) {
+    ReminderUnit.Minutes -> R.string.reminder_unit_minutes
+    ReminderUnit.Hours -> R.string.reminder_unit_hours
+    ReminderUnit.Days -> R.string.reminder_unit_days
+    ReminderUnit.Weeks -> R.string.reminder_unit_weeks
+}
+
+/**
+ * Humanise a reminder lead time (minutes before the event start) into one
+ * line: "Default reminder" (negative = the provider default), "At time of
+ * event" (0), "10 minutes before", "1 hour before", … Shared by the detail
+ * screen, the event form and the default-reminder settings so the wording
+ * never drifts.
+ */
+@Composable
+fun reminderLeadTimeLabel(minutes: Int): String = when {
+    minutes < 0 -> stringResource(R.string.reminder_default)
+    minutes == 0 -> stringResource(R.string.reminder_at_time)
+    minutes % 10_080 == 0 ->
+        pluralStringResource(R.plurals.reminder_weeks, minutes / 10_080, minutes / 10_080)
+    minutes % 1_440 == 0 ->
+        pluralStringResource(R.plurals.reminder_days, minutes / 1_440, minutes / 1_440)
+    minutes % 60 == 0 ->
+        pluralStringResource(R.plurals.reminder_hours, minutes / 60, minutes / 60)
+    else -> pluralStringResource(R.plurals.reminder_minutes, minutes, minutes)
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/TimePickerAlert.kt

@@ -0,0 +1,68 @@
+package de.jeanlucmakiola.calendula.ui.common
+
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import android.content.Context
+import android.content.res.Resources
+import android.provider.Settings
+import android.text.format.DateFormat
+import androidx.compose.material3.TimePicker
+import androidx.compose.material3.rememberTimePickerState
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.res.stringResource
+import de.jeanlucmakiola.calendula.R
+import kotlinx.datetime.LocalTime
+
+/**
+ * M3 time picker in an alert dialog, seeded with [initial]. Shared by the event
+ * form (start/end times) and Settings (the all-day reminder fire time).
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun TimePickerAlert(
+    initial: LocalTime,
+    onConfirm: (LocalTime) -> Unit,
+    onDismiss: () -> Unit,
+) {
+    val state = rememberTimePickerState(
+        initialHour = initial.hour,
+        initialMinute = initial.minute,
+        is24Hour = deviceUses24HourClock(LocalContext.current),
+    )
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        confirmButton = {
+            TextButton(onClick = { onConfirm(LocalTime(state.hour, state.minute)) }) {
+                Text(stringResource(R.string.dialog_ok))
+            }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) { Text(stringResource(R.string.dialog_cancel)) }
+        },
+        text = { TimePicker(state = state) },
+    )
+}
+
+/**
+ * Whether the clock should read 24-hour, matching the rest of the device.
+ *
+ * [DateFormat.is24HourFormat] resolves a "locale default" system setting against
+ * the *app's* context locale — and this app applies a per-app language
+ * (AppCompatDelegate), so an English UI on a German-region phone would wrongly
+ * read 12-hour while the system clock shows 24-hour. So we honour an explicit
+ * system 12/24 override, and otherwise fall back to the **device** locale
+ * (Resources.getSystem), not the app's.
+ */
+private fun deviceUses24HourClock(context: Context): Boolean =
+    when (Settings.System.getString(context.contentResolver, Settings.System.TIME_12_24)) {
+        "24" -> true
+        "12" -> false
+        // 'a' is the AM/PM marker; a best-fit pattern without it is 24-hour.
+        else -> {
+            val deviceLocale = Resources.getSystem().configuration.locales[0]
+            !DateFormat.getBestDateTimePattern(deviceLocale, "jm").contains('a')
+        }
+    }

app/src/main/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailScreen.kt

@@ -41,6 +41,7 @@ import androidx.compose.material.icons.filled.Place
 import androidx.compose.material.icons.filled.Public
 import androidx.compose.material.icons.filled.Repeat
 import androidx.compose.material.icons.filled.Schedule
+import androidx.compose.material.icons.filled.Share
 import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
@@ -59,6 +60,7 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
@@ -67,7 +69,6 @@ import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.platform.LocalContext
 import androidx.core.content.ContextCompat
-import androidx.compose.ui.res.pluralStringResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.AnnotatedString
 import androidx.compose.ui.text.LinkAnnotation
@@ -96,6 +97,8 @@ import de.jeanlucmakiola.calendula.ui.common.OptionCard
 import de.jeanlucmakiola.calendula.ui.common.currentLocale
 import de.jeanlucmakiola.calendula.ui.common.pastelize
 import de.jeanlucmakiola.calendula.ui.common.recurrenceText
+import de.jeanlucmakiola.calendula.ui.common.reminderLeadTimeLabel
+import kotlinx.coroutines.launch
 import kotlinx.datetime.TimeZone
 import java.time.ZoneId
 import java.time.format.DateTimeFormatter
@@ -132,9 +135,30 @@ fun EventDetailScreen(
     BackHandler(onBack = onBack)
 
     val context = LocalContext.current
+    val scope = rememberCoroutineScope()
     val snackbarHostState = remember { SnackbarHostState() }
     var showDeleteDialog by rememberSaveable { mutableStateOf(false) }
 
+    // Sharing is read-only, so it needs no WRITE_CALENDAR upgrade. The VM stages
+    // an .ics in the cache and hands back a content Uri for the chooser.
+    val shareFailedMessage = stringResource(R.string.event_share_failed)
+    val shareChooserTitle = stringResource(R.string.event_share_chooser_title)
+    val onShareClick = {
+        scope.launch {
+            val uri = viewModel.shareUri()
+            val sent = uri != null && runCatching {
+                val send = Intent(Intent.ACTION_SEND).apply {
+                    type = "text/calendar"
+                    putExtra(Intent.EXTRA_STREAM, uri)
+                    addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+                }
+                context.startActivity(Intent.createChooser(send, shareChooserTitle))
+            }.isSuccess
+            if (!sent) snackbarHostState.showSnackbar(shareFailedMessage)
+        }
+        Unit
+    }
+
     // v1.0 installs only hold READ_CALENDAR; the first write asks for the
     // upgrade in place. Granting continues straight into the tapped action.
     var pendingEdit by remember { mutableStateOf(false) }
@@ -203,9 +227,18 @@ fun EventDetailScreen(
                     }
                 },
                 actions = {
-                    // Only writable calendars get actions — WebCal subscriptions,
-                    // birthday calendars etc. are read-only at the provider level.
                     val s = state
+                    // Share works for any loaded event — it only reads the event.
+                    if (s is EventDetailUiState.Success) {
+                        IconButton(onClick = onShareClick) {
+                            Icon(
+                                imageVector = Icons.Default.Share,
+                                contentDescription = stringResource(R.string.event_detail_share),
+                            )
+                        }
+                    }
+                    // Edit/delete need a writable calendar — WebCal subscriptions,
+                    // birthday calendars etc. are read-only at the provider level.
                     if (s is EventDetailUiState.Success && s.canModify) {
                         IconButton(
                             onClick = onEditClick,
@@ -684,26 +717,7 @@ private fun attendeeRoleLabel(attendee: Attendee): Int? = when {
 
 /** Humanise a reminder's lead time, e.g. "10 minutes before" / "At time of event". */
 @Composable
-private fun reminderLeadText(reminder: Reminder): String {
-    val minutes = reminder.minutes
-    return when {
-        minutes < 0 -> stringResource(R.string.reminder_default)
-        minutes == 0 -> stringResource(R.string.reminder_at_time)
-        minutes % 10_080 == 0 -> {
-            val weeks = minutes / 10_080
-            pluralStringResource(R.plurals.reminder_weeks, weeks, weeks)
-        }
-        minutes % 1_440 == 0 -> {
-            val days = minutes / 1_440
-            pluralStringResource(R.plurals.reminder_days, days, days)
-        }
-        minutes % 60 == 0 -> {
-            val hours = minutes / 60
-            pluralStringResource(R.plurals.reminder_hours, hours, hours)
-        }
-        else -> pluralStringResource(R.plurals.reminder_minutes, minutes, minutes)
-    }
-}
+private fun reminderLeadText(reminder: Reminder): String = reminderLeadTimeLabel(reminder.minutes)
 
 /**
  * A localized label for [tz] (e.g. "Central European Time (Europe/Berlin)"),
@@ -762,14 +776,19 @@ private fun formatWhen(
     val allDayLabel = stringResource(R.string.event_detail_all_day)
 
     if (instance.isAllDay) {
-        // All-day end is the exclusive next midnight; step back to the last
-        // covered day so a one-day event reads as a single date.
-        val lastLdt = (instance.end - 1.seconds).toJavaLocalDateTime(zid)
-        return if (startLdt.toLocalDate() == lastLdt.toLocalDate()) {
-            allDayLabel to dateFull.format(startLdt.toLocalDate())
+        // All-day events live at UTC midnights with an exclusive end. Resolve
+        // the covered dates in UTC — not the device zone, which would shift the
+        // midnight boundaries off the intended date (east of UTC pushes the
+        // end past the last day; west of UTC pulls the start back) — and step
+        // the end back to the last covered day so a one-day event reads as a
+        // single date.
+        val utc = ZoneId.of("UTC")
+        val startDate = instance.start.toJavaLocalDateTime(utc).toLocalDate()
+        val lastDate = (instance.end - 1.seconds).toJavaLocalDateTime(utc).toLocalDate()
+        return if (startDate == lastDate) {
+            allDayLabel to dateFull.format(startDate)
         } else {
-            allDayLabel to
-                "${dateMedium.format(startLdt.toLocalDate())} – ${dateMedium.format(lastLdt.toLocalDate())}"
+            allDayLabel to "${dateMedium.format(startDate)} – ${dateMedium.format(lastDate)}"
         }
     }
 

app/src/main/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailViewModel.kt

@@ -1,14 +1,20 @@
 package de.jeanlucmakiola.calendula.ui.detail
 
+import android.net.Uri
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
 import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
 import de.jeanlucmakiola.calendula.data.calendar.NoSuchEventException
 import de.jeanlucmakiola.calendula.data.di.IoDispatcher
+import de.jeanlucmakiola.calendula.data.ics.IcsExporter
 import de.jeanlucmakiola.calendula.domain.FailureReason
 import de.jeanlucmakiola.calendula.domain.RecurringWriteScope
+import de.jeanlucmakiola.calendula.domain.ics.IcsWriter
+import de.jeanlucmakiola.calendula.domain.ics.toShareIcsEvent
 import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.withContext
+import kotlin.time.Clock
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
@@ -34,6 +40,7 @@ import javax.inject.Inject
 @HiltViewModel
 class EventDetailViewModel @Inject constructor(
     private val repository: CalendarRepository,
+    private val icsExporter: IcsExporter,
     @IoDispatcher private val io: CoroutineDispatcher,
 ) : ViewModel() {
 
@@ -113,6 +120,24 @@ class EventDetailViewModel @Inject constructor(
         _deleteState.value = DeleteUiState.Idle
     }
 
+    /**
+     * Serialise the open event to a `.ics` cache file and return a shareable
+     * content Uri (for an ACTION_SEND), or null when nothing is loaded or the
+     * write fails. The event is exported as a one-off (see [toShareIcsEvent]).
+     */
+    suspend fun shareUri(): Uri? {
+        val detail = (state.value as? EventDetailUiState.Success)?.detail ?: return null
+        return runCatching {
+            withContext(io) {
+                val ics = IcsWriter().writeCalendar(
+                    events = listOf(detail.toShareIcsEvent()),
+                    dtStamp = Clock.System.now(),
+                )
+                icsExporter.stageShareFile(shareFileName(detail.instance.title), ics)
+            }
+        }.getOrNull()
+    }
+
     private suspend fun loadDetail(target: Target): EventDetailUiState = try {
         val detail = repository.eventDetail(target.eventId)
         // The Events row holds the series start; replace it with this
@@ -143,3 +168,13 @@ class EventDetailViewModel @Inject constructor(
     /** A tapped occurrence: the series [eventId] plus this occurrence's own times. */
     private data class Target(val eventId: Long, val beginMillis: Long, val endMillis: Long)
 }
+
+/** A filesystem-safe `.ics` file name from an event title (or a fallback). */
+private fun shareFileName(title: String): String {
+    val base = title.trim()
+        .replace(Regex("""[^\p{L}\p{Nd} _-]"""), "")
+        .replace(' ', '_')
+        .take(40)
+        .ifBlank { "event" }
+    return "$base.ics"
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditScreen.kt

@@ -68,10 +68,8 @@ import androidx.compose.material3.Surface
 import androidx.compose.material3.Switch
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
-import androidx.compose.material3.TimePicker
 import androidx.compose.material3.TopAppBar
 import androidx.compose.material3.TopAppBarDefaults
-import androidx.compose.material3.rememberTimePickerState
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
@@ -86,7 +84,6 @@ import androidx.compose.ui.graphics.SolidColor
 import androidx.compose.ui.graphics.isSpecified
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.platform.LocalContext
-import androidx.compose.ui.res.pluralStringResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.AnnotatedString
 import androidx.compose.ui.text.TextStyle
@@ -101,6 +98,7 @@ import de.jeanlucmakiola.calendula.domain.AccessLevel
 import de.jeanlucmakiola.calendula.domain.Availability
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventColorOption
+import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventFormField
 import de.jeanlucmakiola.calendula.domain.EventFormProblem
 import de.jeanlucmakiola.calendula.domain.RecurrenceEnd
@@ -112,10 +110,17 @@ import de.jeanlucmakiola.calendula.domain.toRRule
 import de.jeanlucmakiola.calendula.ui.common.CALENDAR_COLOR_PALETTE
 import de.jeanlucmakiola.calendula.ui.common.CalendarDatePickerDialog
 import de.jeanlucmakiola.calendula.ui.common.ColorSwatchRow
+import de.jeanlucmakiola.calendula.ui.common.DialogAmountField
+import de.jeanlucmakiola.calendula.ui.common.DialogUnitDropdown
 import de.jeanlucmakiola.calendula.ui.common.MILLIS_PER_DAY
 import de.jeanlucmakiola.calendula.ui.common.InlineTextField
 import de.jeanlucmakiola.calendula.ui.common.OptionCard
+import de.jeanlucmakiola.calendula.ui.common.REMINDER_PRESETS
+import de.jeanlucmakiola.calendula.ui.common.ReminderUnit
+import de.jeanlucmakiola.calendula.ui.common.TimePickerAlert
 import de.jeanlucmakiola.calendula.ui.common.currentLocale
+import de.jeanlucmakiola.calendula.ui.common.reminderLeadTimeLabel
+import de.jeanlucmakiola.calendula.ui.common.reminderUnitLabel
 import de.jeanlucmakiola.calendula.ui.common.pastelize
 import de.jeanlucmakiola.calendula.ui.common.recurrenceText
 import kotlinx.datetime.DayOfWeek
@@ -152,19 +157,23 @@ fun EventEditScreen(
     onSaved: () -> Unit,
     editKey: LongArray? = null,
     initialStartMinutes: Int? = null,
+    initialForm: EventForm? = null,
     viewModel: EventEditViewModel = hiltViewModel(),
 ) {
-    LaunchedEffect(initialDateIso, editKey) {
-        if (editKey != null) {
-            viewModel.openForEdit(
+    LaunchedEffect(initialDateIso, editKey, initialForm) {
+        when {
+            // Single-event .ics open: the form arrives prefilled for review.
+            initialForm != null -> viewModel.openImported(initialForm)
+            editKey != null -> viewModel.openForEdit(
                 eventId = editKey[0],
                 beginMillis = editKey[1],
                 endMillis = editKey[2],
             )
-        } else {
-            val date = initialDateIso?.let { runCatching { LocalDate.parse(it) }.getOrNull() }
-                ?: Clock.System.now().toLocalDateTime(TimeZone.currentSystemDefault()).date
-            viewModel.openNew(date, initialStartMinutes)
+            else -> {
+                val date = initialDateIso?.let { runCatching { LocalDate.parse(it) }.getOrNull() }
+                    ?: Clock.System.now().toLocalDateTime(TimeZone.currentSystemDefault()).date
+                viewModel.openNew(date, initialStartMinutes)
+            }
         }
     }
     val state by viewModel.state.collectAsStateWithLifecycle()
@@ -916,14 +925,7 @@ private fun FieldPickerDialog(
 }
 
 /** Quick-pick lead times offered as chips in the reminder dialog. */
-private val REMINDER_QUICK_PICKS = listOf(0, 10, 30, 60, 1_440)
-
-private enum class ReminderUnit(val minutesFactor: Int) {
-    Minutes(1),
-    Hours(60),
-    Days(1_440),
-    Weeks(10_080),
-}
+private val REMINDER_QUICK_PICKS = REMINDER_PRESETS
 
 /**
  * Reminder picker, two steps: the common lead times as a tappable list
@@ -1245,84 +1247,6 @@ private fun Set<DayOfWeek>.toMask(): Int = fold(0) { acc, day -> acc or day.toMa
 private fun Int.toDaySet(): Set<DayOfWeek> =
     DayOfWeek.entries.filter { this and it.toMaskBit() != 0 }.toSet()
 
-/** Tonal 3-digit number input shared by the custom reminder/recurrence steps. */
-@Composable
-private fun DialogAmountField(
-    value: String,
-    onValueChange: (String) -> Unit,
-    placeholder: String,
-) {
-    // surfaceContainerHighest — the dialog itself sits on
-    // surfaceContainerHigh, so anything lower vanishes.
-    Surface(
-        color = MaterialTheme.colorScheme.surfaceContainerHighest,
-        shape = RoundedCornerShape(12.dp),
-    ) {
-        InlineField(
-            value = value,
-            onValueChange = { text ->
-                if (text.length <= 3 && text.all(Char::isDigit)) {
-                    onValueChange(text)
-                }
-            },
-            placeholder = placeholder,
-            textStyle = MaterialTheme.typography.titleMedium,
-            keyboardType = KeyboardType.Number,
-            modifier = Modifier
-                .width(72.dp)
-                .padding(horizontal = 14.dp, vertical = 12.dp),
-        )
-    }
-}
-
-/** Tonal dropdown trigger + menu shared by the custom reminder/recurrence steps. */
-@Composable
-private fun DialogUnitDropdown(
-    label: String,
-    entries: List<String>,
-    onPick: (Int) -> Unit,
-) {
-    var open by remember { mutableStateOf(false) }
-    Box {
-        Surface(
-            color = MaterialTheme.colorScheme.surfaceContainerHighest,
-            shape = RoundedCornerShape(12.dp),
-            onClick = { open = true },
-        ) {
-            Row(
-                verticalAlignment = Alignment.CenterVertically,
-                modifier = Modifier.padding(
-                    start = 14.dp,
-                    end = 8.dp,
-                    top = 12.dp,
-                    bottom = 12.dp,
-                ),
-            ) {
-                Text(
-                    text = label,
-                    style = MaterialTheme.typography.titleMedium,
-                )
-                Spacer(Modifier.width(4.dp))
-                Icon(
-                    imageVector = Icons.Default.ArrowDropDown,
-                    contentDescription = null,
-                    tint = MaterialTheme.colorScheme.onSurfaceVariant,
-                )
-            }
-        }
-        DropdownMenu(expanded = open, onDismissRequest = { open = false }) {
-            entries.forEachIndexed { index, entry ->
-                DropdownMenuItem(
-                    text = { Text(entry) },
-                    onClick = {
-                        onPick(index)
-                        open = false
-                    },
-                )
-            }
-        }
-    }
-}
 
 private fun recurrencePresetLabel(freq: RecurrenceFreq): Int = when (freq) {
     RecurrenceFreq.Daily -> R.string.recurrence_daily
@@ -1377,13 +1301,6 @@ private fun AddReminderChip(onClick: () -> Unit) {
     )
 }
 
-private fun reminderUnitLabel(unit: ReminderUnit): Int = when (unit) {
-    ReminderUnit.Minutes -> R.string.reminder_unit_minutes
-    ReminderUnit.Hours -> R.string.reminder_unit_hours
-    ReminderUnit.Days -> R.string.reminder_unit_days
-    ReminderUnit.Weeks -> R.string.reminder_unit_weeks
-}
-
 private fun fieldLabel(field: EventFormField): Int = when (field) {
     EventFormField.Location -> R.string.event_detail_location
     EventFormField.Description -> R.string.event_detail_description
@@ -1517,16 +1434,7 @@ private fun accessLevelLabel(level: AccessLevel): Int = when (level) {
 
 /** Humanise a reminder lead time, mirroring the detail screen's rendering. */
 @Composable
-private fun reminderLabel(minutes: Int): String = when {
-    minutes <= 0 -> stringResource(R.string.reminder_at_time)
-    minutes % 10_080 == 0 ->
-        pluralStringResource(R.plurals.reminder_weeks, minutes / 10_080, minutes / 10_080)
-    minutes % 1_440 == 0 ->
-        pluralStringResource(R.plurals.reminder_days, minutes / 1_440, minutes / 1_440)
-    minutes % 60 == 0 ->
-        pluralStringResource(R.plurals.reminder_hours, minutes / 60, minutes / 60)
-    else -> pluralStringResource(R.plurals.reminder_minutes, minutes, minutes)
-}
+private fun reminderLabel(minutes: Int): String = reminderLeadTimeLabel(minutes)
 
 /**
  * One info card mirroring the detail screen's DetailCard: tonal container,
@@ -1687,31 +1595,6 @@ private fun ScheduleRow(
     }
 }
 
-@OptIn(ExperimentalMaterial3Api::class)
-@Composable
-private fun TimePickerAlert(
-    initial: LocalTime,
-    onConfirm: (LocalTime) -> Unit,
-    onDismiss: () -> Unit,
-) {
-    val state = rememberTimePickerState(
-        initialHour = initial.hour,
-        initialMinute = initial.minute,
-    )
-    AlertDialog(
-        onDismissRequest = onDismiss,
-        confirmButton = {
-            TextButton(onClick = { onConfirm(LocalTime(state.hour, state.minute)) }) {
-                Text(stringResource(R.string.dialog_ok))
-            }
-        },
-        dismissButton = {
-            TextButton(onClick = onDismiss) { Text(stringResource(R.string.dialog_cancel)) }
-        },
-        text = { TimePicker(state = state) },
-    )
-}
-
 @Composable
 private fun CalendarPickerDialog(
     calendars: List<CalendarSource>,

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditViewModel.kt

@@ -8,6 +8,7 @@ import de.jeanlucmakiola.calendula.data.calendar.NoSuchEventException
 import de.jeanlucmakiola.calendula.data.di.IoDispatcher
 import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
 import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
+import de.jeanlucmakiola.calendula.data.prefs.resolveDefaultReminder
 import de.jeanlucmakiola.calendula.domain.AccessLevel
 import de.jeanlucmakiola.calendula.domain.Availability
 import de.jeanlucmakiola.calendula.domain.CalendarSource
@@ -29,6 +30,7 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.flatMapLatest
 import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.flowOn
@@ -71,6 +73,10 @@ class EventEditViewModel @Inject constructor(
     // Set while the form edits an existing event instead of composing a new one.
     private val _editTarget = MutableStateFlow<EditTarget?>(null)
     private val _loadFailed = MutableStateFlow(false)
+    // True once the user has hand-edited the reminders on a new event, which
+    // freezes the auto-applied default: switching calendars no longer overwrites
+    // their choice. Reset with the form.
+    private val _remindersTouched = MutableStateFlow(false)
 
     /** True when the event to edit couldn't be loaded; the screen closes itself. */
     val loadFailed: StateFlow<Boolean> = _loadFailed.asStateFlow()
@@ -100,6 +106,13 @@ class EventEditViewModel @Inject constructor(
         val editTarget: EditTarget?,
     )
 
+    private data class ReminderDefaults(
+        val timed: Int?,
+        val allDay: Int?,
+        val timedOverrides: Map<Long, Int?>,
+        val allDayOverrides: Map<Long, Int?>,
+    )
+
     private data class ExternalInputs(
         val writable: List<CalendarSource>,
         val lastUsed: Long?,
@@ -194,6 +207,63 @@ class EventEditViewModel @Inject constructor(
         }
         val end = (start.toInstant(zone) + 1.hours).toLocalDateTime(zone)
         _form.value = EventForm(calendarId = null, start = start, end = end)
+        applyDefaultReminder()
+    }
+
+    /**
+     * Seed a fresh event from a parsed `.ics` file (the single-event "open into
+     * the create form" path). [form] already carries the file's fields; its
+     * [EventForm.calendarId] is null so the calendar still resolves to the
+     * last-used/first-writable one, and reminders are frozen as touched so the
+     * settings default never overwrites what the file specified. No-op when a
+     * form is already open, so the prefill survives configuration changes.
+     */
+    fun openImported(form: EventForm) {
+        if (_form.value != null || _editTarget.value != null) return
+        _remindersTouched.value = true
+        _revealed.value = form.populatedFields()
+        _form.value = form
+    }
+
+    /**
+     * Prefill a new event's reminders from the settings default — the all-day
+     * default for all-day events, otherwise the resolved calendar's per-calendar
+     * override or the global timed default. No-op while editing an existing event
+     * or once the user has hand-edited the reminders, so the auto-default never
+     * clobbers a manual choice. [calendarId] short-circuits the resolution after a
+     * calendar switch; null resolves it as the form does.
+     */
+    private fun applyDefaultReminder(calendarId: Long? = null) {
+        if (_editTarget.value != null || _remindersTouched.value) return
+        viewModelScope.launch {
+            val defaults = combine(
+                settingsPrefs.defaultReminderMinutes,
+                settingsPrefs.defaultAllDayReminderMinutes,
+                settingsPrefs.perCalendarReminderOverride,
+                settingsPrefs.perCalendarAllDayReminderOverride,
+            ) { timed, allDay, timedOv, allDayOv ->
+                ReminderDefaults(timed, allDay, timedOv, allDayOv)
+            }.first()
+            val targetId = calendarId ?: resolvedCalendarId.first()
+            // Re-check after suspending: bail if the form closed or the user edited.
+            val form = _form.value ?: return@launch
+            if (_editTarget.value != null || _remindersTouched.value) return@launch
+            val default = resolveDefaultReminder(
+                timedGlobal = defaults.timed,
+                allDayGlobal = defaults.allDay,
+                timedOverrides = defaults.timedOverrides,
+                allDayOverrides = defaults.allDayOverrides,
+                calendarId = targetId,
+                isAllDay = form.isAllDay,
+            )
+            val reminders = listOfNotNull(default)
+            _form.value = form.copy(reminders = reminders)
+            // Surface the section so an auto-applied default is visible and
+            // removable, even when Reminders isn't a default-shown field.
+            if (reminders.isNotEmpty()) {
+                _revealed.value = _revealed.value + EventFormField.Reminders
+            }
+        }
     }
 
     /**
@@ -229,6 +299,7 @@ class EventEditViewModel @Inject constructor(
         _revealed.value = emptySet()
         _editTarget.value = null
         _loadFailed.value = false
+        _remindersTouched.value = false
     }
 
     /** Unfold one optional field, picked in the "more fields" dialog. */
@@ -239,14 +310,24 @@ class EventEditViewModel @Inject constructor(
     fun setTitle(value: String) = update { it.copy(title = value) }
     fun setLocation(value: String) = update { it.copy(location = value) }
     fun setDescription(value: String) = update { it.copy(description = value) }
-    fun setAllDay(value: Boolean) = update { it.copy(isAllDay = value) }
+    fun setAllDay(value: Boolean) {
+        update { it.copy(isAllDay = value) }
+        // The default reminder differs for all-day vs timed; re-apply the
+        // type-appropriate default unless the user has hand-edited it (guarded).
+        applyDefaultReminder()
+    }
 
     /**
      * Switching calendars drops any chosen colour: a palette key is
      * account-scoped, and a raw colour may be invalid on the new calendar.
      * The event falls back to the new calendar's colour until re-picked.
      */
-    fun setCalendar(id: Long) = update { it.copy(calendarId = id, colorKey = null, color = null) }
+    fun setCalendar(id: Long) {
+        update { it.copy(calendarId = id, colorKey = null, color = null) }
+        // A fresh event re-inherits the new calendar's default reminder unless
+        // the user has already hand-edited it (guarded inside).
+        applyDefaultReminder(id)
+    }
     fun setAvailability(value: Availability) = update { it.copy(availability = value) }
     fun setAccessLevel(value: AccessLevel) = update { it.copy(accessLevel = value) }
 
@@ -262,12 +343,14 @@ class EventEditViewModel @Inject constructor(
     /** Bare RRULE value from the recurrence picker; null = does not repeat. */
     fun setRecurrence(rrule: String?) = update { it.copy(rrule = rrule) }
 
-    fun addReminder(minutes: Int) = update {
-        it.copy(reminders = (it.reminders + minutes).distinct().sorted())
+    fun addReminder(minutes: Int) {
+        _remindersTouched.value = true
+        update { it.copy(reminders = (it.reminders + minutes).distinct().sorted()) }
     }
 
-    fun removeReminder(minutes: Int) = update {
-        it.copy(reminders = it.reminders - minutes)
+    fun removeReminder(minutes: Int) {
+        _remindersTouched.value = true
+        update { it.copy(reminders = it.reminders - minutes) }
     }
 
     /** Moving the start drags the end along, preserving the duration. */

app/src/main/java/de/jeanlucmakiola/calendula/ui/imports/ImportScreen.kt

@@ -0,0 +1,207 @@
+package de.jeanlucmakiola.calendula.ui.imports
+
+import android.net.Uri
+import androidx.activity.compose.BackHandler
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Close
+import androidx.compose.material3.Button
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.material3.TopAppBarDefaults
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.pluralStringResource
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.unit.dp
+import androidx.hilt.navigation.compose.hiltViewModel
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import de.jeanlucmakiola.calendula.R
+import de.jeanlucmakiola.calendula.domain.EventForm
+import de.jeanlucmakiola.calendula.domain.ics.IcsParseWarning
+import de.jeanlucmakiola.calendula.ui.common.OptionCard
+
+/**
+ * Handles an opened/received `.ics` file. A single event is handed straight to
+ * the prefilled create form via [onOpenSingle]; several events show a target-
+ * calendar picker and import in bulk (dedup by UID), then a result summary.
+ * Empty/failed files show a short message and close.
+ */
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun ImportScreen(
+    uri: Uri,
+    onClose: () -> Unit,
+    onOpenSingle: (EventForm) -> Unit,
+    viewModel: ImportViewModel = hiltViewModel(),
+) {
+    LaunchedEffect(uri) { viewModel.load(uri) }
+    val state by viewModel.state.collectAsStateWithLifecycle()
+    BackHandler(onBack = onClose)
+
+    // A single event isn't shown here — it opens the create form for review.
+    LaunchedEffect(state) {
+        (state as? ImportUiState.Single)?.let { onOpenSingle(it.form); onClose() }
+    }
+
+    Scaffold(
+        modifier = Modifier.fillMaxSize(),
+        topBar = {
+            TopAppBar(
+                title = { Text(stringResource(R.string.import_title)) },
+                navigationIcon = {
+                    IconButton(onClick = onClose) {
+                        Icon(Icons.Default.Close, contentDescription = stringResource(R.string.event_edit_close))
+                    }
+                },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = MaterialTheme.colorScheme.surface,
+                ),
+            )
+        },
+    ) { padding ->
+        Box(Modifier.fillMaxSize().padding(padding)) {
+            when (val s = state) {
+                ImportUiState.Loading,
+                ImportUiState.Importing,
+                is ImportUiState.Single,
+                -> CircularProgressIndicator(Modifier.align(Alignment.Center))
+
+                ImportUiState.Empty -> CenteredMessage(stringResource(R.string.import_empty), onClose)
+                ImportUiState.Failed -> CenteredMessage(stringResource(R.string.import_failed), onClose)
+                is ImportUiState.Many -> ManyContent(s, onImport = viewModel::import)
+                is ImportUiState.Done -> DoneContent(s, onClose)
+            }
+        }
+    }
+}
+
+@Composable
+private fun ManyContent(state: ImportUiState.Many, onImport: (Long) -> Unit) {
+    // No writable calendar to import into — tell the user honestly.
+    if (state.calendars.isEmpty()) {
+        CenteredMessage(stringResource(R.string.import_no_calendar), onClose = null)
+        return
+    }
+    var selected by rememberSaveable { mutableStateOf(state.calendars.first().id) }
+
+    Column(
+        Modifier.fillMaxSize().verticalScroll(rememberScrollState())
+            .padding(horizontal = 16.dp, vertical = 8.dp),
+        verticalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        Text(
+            pluralStringResource(R.plurals.import_event_count, state.events.size, state.events.size),
+            style = MaterialTheme.typography.bodyLarge,
+            modifier = Modifier.padding(vertical = 8.dp),
+        )
+        Text(
+            stringResource(R.string.import_target_header),
+            style = MaterialTheme.typography.labelLarge,
+            color = MaterialTheme.colorScheme.primary,
+        )
+        state.calendars.forEach { calendar ->
+            OptionCard(
+                label = calendar.displayName,
+                onClick = { selected = calendar.id },
+                selected = calendar.id == selected,
+                icon = null,
+            )
+        }
+        state.warnings.forEach { WarningText(it) }
+        Button(
+            onClick = { onImport(selected) },
+            modifier = Modifier.fillMaxWidth().padding(top = 8.dp),
+        ) {
+            Text(pluralStringResource(R.plurals.import_action, state.events.size, state.events.size))
+        }
+    }
+}
+
+@Composable
+private fun DoneContent(state: ImportUiState.Done, onClose: () -> Unit) {
+    Column(
+        Modifier.fillMaxSize().padding(24.dp),
+        verticalArrangement = Arrangement.spacedBy(12.dp),
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        Text(
+            stringResource(R.string.import_done_title),
+            style = MaterialTheme.typography.headlineSmall,
+            modifier = Modifier.padding(top = 24.dp),
+        )
+        Text(
+            pluralStringResource(
+                R.plurals.import_done_imported,
+                state.summary.imported,
+                state.summary.imported,
+            ),
+            style = MaterialTheme.typography.bodyLarge,
+        )
+        if (state.summary.skippedDuplicate > 0) {
+            Text(
+                pluralStringResource(
+                    R.plurals.import_done_skipped,
+                    state.summary.skippedDuplicate,
+                    state.summary.skippedDuplicate,
+                ),
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+        Button(onClick = onClose, modifier = Modifier.padding(top = 12.dp)) {
+            Text(stringResource(R.string.import_close))
+        }
+    }
+}
+
+@Composable
+private fun WarningText(warning: IcsParseWarning) {
+    val text = when (warning) {
+        IcsParseWarning.ModifiedOccurrenceSkipped -> stringResource(R.string.import_warning_recurrence)
+        IcsParseWarning.EventWithoutStartSkipped -> stringResource(R.string.import_warning_no_start)
+        IcsParseWarning.AttendeesIgnored -> stringResource(R.string.import_warning_attendees)
+        IcsParseWarning.UnknownTimezone -> stringResource(R.string.import_warning_timezone)
+    }
+    Text(
+        text = text,
+        style = MaterialTheme.typography.bodySmall,
+        color = MaterialTheme.colorScheme.onSurfaceVariant,
+    )
+}
+
+@Composable
+private fun CenteredMessage(message: String, onClose: (() -> Unit)?) {
+    Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+        Column(
+            Modifier.padding(24.dp),
+            verticalArrangement = Arrangement.spacedBy(16.dp),
+            horizontalAlignment = Alignment.CenterHorizontally,
+        ) {
+            Text(message, style = MaterialTheme.typography.bodyLarge)
+            if (onClose != null) {
+                Button(onClick = onClose) { Text(stringResource(R.string.import_close)) }
+            }
+        }
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/imports/ImportViewModel.kt

@@ -0,0 +1,105 @@
+package de.jeanlucmakiola.calendula.ui.imports
+
+import android.net.Uri
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import dagger.hilt.android.lifecycle.HiltViewModel
+import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
+import de.jeanlucmakiola.calendula.data.di.IoDispatcher
+import de.jeanlucmakiola.calendula.data.ics.IcsImporter
+import de.jeanlucmakiola.calendula.domain.CalendarSource
+import de.jeanlucmakiola.calendula.domain.EventForm
+import de.jeanlucmakiola.calendula.domain.ics.IcsImportSummary
+import de.jeanlucmakiola.calendula.domain.ics.IcsParseWarning
+import de.jeanlucmakiola.calendula.domain.ics.IcsParser
+import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
+import de.jeanlucmakiola.calendula.domain.ics.toEventForm
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import kotlinx.datetime.TimeZone
+import kotlin.coroutines.cancellation.CancellationException
+import javax.inject.Inject
+
+/** What an opened/received `.ics` resolved to. */
+sealed interface ImportUiState {
+    data object Loading : ImportUiState
+    data object Importing : ImportUiState
+
+    /** The file held no importable event (or couldn't be read/parsed as one). */
+    data object Empty : ImportUiState
+    data object Failed : ImportUiState
+
+    /** Exactly one event → review it in the prefilled create form. */
+    data class Single(val form: EventForm, val warnings: Set<IcsParseWarning>) : ImportUiState
+
+    /** Several events → pick a target calendar and bulk-import. */
+    data class Many(
+        val events: List<ParsedIcsEvent>,
+        val warnings: Set<IcsParseWarning>,
+        val calendars: List<CalendarSource>,
+    ) : ImportUiState
+
+    data class Done(val summary: IcsImportSummary) : ImportUiState
+}
+
+/**
+ * Reads an `.ics` [Uri], parses it (pure [IcsParser]) and routes by event count:
+ * one event opens the create form for review, many open the bulk-import picker.
+ * The bulk import dedups by UID in the repository.
+ */
+@HiltViewModel
+class ImportViewModel @Inject constructor(
+    private val repository: CalendarRepository,
+    private val importer: IcsImporter,
+    @IoDispatcher private val io: CoroutineDispatcher,
+) : ViewModel() {
+
+    private val parser = IcsParser()
+    private val _state = MutableStateFlow<ImportUiState>(ImportUiState.Loading)
+    val state: StateFlow<ImportUiState> = _state.asStateFlow()
+    private var started = false
+
+    /** Read + parse [uri] once; subsequent calls (recomposition) are ignored. */
+    fun load(uri: Uri) {
+        if (started) return
+        started = true
+        viewModelScope.launch {
+            val parsed = withContext(io) {
+                importer.readText(uri)?.let(parser::parse)
+            }
+            _state.value = when {
+                parsed == null -> ImportUiState.Failed
+                parsed.events.isEmpty() -> ImportUiState.Empty
+                parsed.events.size == 1 -> ImportUiState.Single(
+                    form = parsed.events.single().toEventForm(TimeZone.currentSystemDefault()),
+                    warnings = parsed.warnings,
+                )
+                else -> ImportUiState.Many(
+                    events = parsed.events,
+                    warnings = parsed.warnings,
+                    calendars = repository.calendars().first().filter { it.canModifyContents },
+                )
+            }
+        }
+    }
+
+    /** Bulk-import the parsed events into [targetCalendarId]; result → [ImportUiState.Done]. */
+    fun import(targetCalendarId: Long) {
+        val many = _state.value as? ImportUiState.Many ?: return
+        viewModelScope.launch {
+            _state.value = ImportUiState.Importing
+            _state.value = try {
+                ImportUiState.Done(repository.importEvents(targetCalendarId, many.events))
+            } catch (e: CancellationException) {
+                throw e
+            } catch (e: Exception) {
+                ImportUiState.Failed
+            }
+        }
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/AppLanguage.kt

@@ -1,36 +1,78 @@
 package de.jeanlucmakiola.calendula.ui.settings
 
+import android.content.Context
 import androidx.appcompat.app.AppCompatDelegate
 import androidx.core.os.LocaleListCompat
+import de.jeanlucmakiola.calendula.R
+import org.xmlpull.v1.XmlPullParser
+import java.util.Locale
 
-/** UI-facing language choice. AUTO follows the system languages. */
-enum class LanguagePref { AUTO, GERMAN, ENGLISH }
+private const val ANDROID_NS = "http://schemas.android.com/apk/res/android"
 
 /**
- * Per-app language via AppCompatDelegate. On API 33+ this delegates to the
- * platform per-app-languages API; below that the appcompat backport persists
- * the choice itself (manifest `autoStoreLocales` service), so we don't mirror
- * it in DataStore. Setting a locale recreates the activity, which re-reads the
- * current value for the dropdown.
+ * Per-app language via AppCompatDelegate, driven by res/xml/locales_config.xml.
+ *
+ * That file is the single source of truth for which languages we ship: dropping
+ * in a values-<tag> translation and adding a matching `<locale>` entry makes the
+ * language show up here and in the system per-app-language settings, with no
+ * other code change. The system-default choice is represented as `null`.
+ *
+ * On API 33+ this delegates to the platform per-app-languages API; below that
+ * the appcompat backport persists the choice itself (manifest `autoStoreLocales`
+ * service), so we don't mirror it in DataStore. Setting a locale recreates the
+ * activity, which re-reads the current value for the picker.
  */
 object AppLanguage {
 
-    fun current(): LanguagePref {
-        val locales = AppCompatDelegate.getApplicationLocales()
-        if (locales.isEmpty) return LanguagePref.AUTO
-        return when (locales[0]?.language) {
-            "de" -> LanguagePref.GERMAN
-            "en" -> LanguagePref.ENGLISH
-            else -> LanguagePref.AUTO
+    /**
+     * The BCP-47 tags the app ships translations for, in declaration order, as
+     * listed in locales_config.xml. Returns whatever could be parsed; a missing
+     * or malformed config yields an empty list (the picker then offers only the
+     * system-default entry rather than crashing).
+     */
+    fun supportedTags(context: Context): List<String> {
+        val tags = mutableListOf<String>()
+        val parser = context.resources.getXml(R.xml.locales_config)
+        try {
+            var event = parser.eventType
+            while (event != XmlPullParser.END_DOCUMENT) {
+                if (event == XmlPullParser.START_TAG && parser.name == "locale") {
+                    parser.getAttributeValue(ANDROID_NS, "name")?.let(tags::add)
+                }
+                event = parser.next()
+            }
+        } catch (_: Exception) {
+            // Fall back to whatever was parsed before the failure.
+        } finally {
+            parser.close()
         }
+        return tags
     }
 
-    fun apply(pref: LanguagePref) {
-        val locales = when (pref) {
-            LanguagePref.AUTO -> LocaleListCompat.getEmptyLocaleList()
-            LanguagePref.GERMAN -> LocaleListCompat.forLanguageTags("de")
-            LanguagePref.ENGLISH -> LocaleListCompat.forLanguageTags("en")
+    /** The applied app language as a BCP-47 tag, or `null` when following the system. */
+    fun currentTag(): String? {
+        val locales = AppCompatDelegate.getApplicationLocales()
+        return if (locales.isEmpty) null else locales[0]?.toLanguageTag()
+    }
+
+    /** Apply a BCP-47 tag, or `null` to follow the system languages. */
+    fun apply(tag: String?) {
+        val locales = if (tag == null) {
+            LocaleListCompat.getEmptyLocaleList()
+        } else {
+            LocaleListCompat.forLanguageTags(tag)
         }
         AppCompatDelegate.setApplicationLocales(locales)
     }
+
+    /**
+     * The autonym for a tag — the language's own name in its own script, e.g.
+     * "Deutsch", "English", "Français" — so users find their language regardless
+     * of the current UI language. Capitalised per the language's own rules.
+     */
+    fun displayName(tag: String): String {
+        val locale = Locale.forLanguageTag(tag)
+        return locale.getDisplayName(locale)
+            .replaceFirstChar { if (it.isLowerCase()) it.titlecase(locale) else it.toString() }
+    }
 }

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsScreen.kt

@@ -5,6 +5,9 @@ import android.content.Context
 import android.content.Intent
 import android.content.pm.PackageManager
 import android.os.Build
+import android.os.PowerManager
+import android.provider.Settings
+import android.text.format.DateFormat
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.animation.AnimatedVisibility
@@ -31,20 +34,22 @@ import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.CalendarMonth
+import androidx.compose.material.icons.filled.Check
+import androidx.compose.material.icons.filled.ExpandLess
+import androidx.compose.material.icons.filled.ExpandMore
 import androidx.compose.material.icons.filled.Gavel
 import androidx.compose.material.icons.filled.Language
 import androidx.compose.material.icons.filled.Notifications
 import androidx.compose.material.icons.filled.Palette
 import androidx.compose.material.icons.filled.Tune
-import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Surface
 import androidx.compose.material3.Switch
 import androidx.compose.material3.Text
-import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -63,17 +68,28 @@ import androidx.compose.ui.unit.dp
 import androidx.core.content.ContextCompat
 import androidx.core.net.toUri
 import androidx.hilt.navigation.compose.hiltViewModel
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleEventObserver
+import androidx.lifecycle.compose.LocalLifecycleOwner
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import de.jeanlucmakiola.calendula.R
+import de.jeanlucmakiola.calendula.data.prefs.CalendarReminderOverride
 import de.jeanlucmakiola.calendula.data.prefs.ThemeMode
 import de.jeanlucmakiola.calendula.data.prefs.WeekStartPref
 import de.jeanlucmakiola.calendula.domain.EventFormField
 import de.jeanlucmakiola.calendula.ui.common.CollapsingScaffold
 import de.jeanlucmakiola.calendula.ui.common.GroupedRow
-import de.jeanlucmakiola.calendula.ui.common.OptionCard
+import de.jeanlucmakiola.calendula.ui.common.CalendarColorChip
+import de.jeanlucmakiola.calendula.ui.common.OptionPicker
 import de.jeanlucmakiola.calendula.ui.common.Position
+import de.jeanlucmakiola.calendula.ui.common.REMINDER_PRESETS
+import de.jeanlucmakiola.calendula.ui.common.ReminderDefaultPicker
+import de.jeanlucmakiola.calendula.ui.common.TimePickerAlert
 import de.jeanlucmakiola.calendula.ui.common.positionOf
+import de.jeanlucmakiola.calendula.ui.common.reminderLeadTimeLabel
 import de.jeanlucmakiola.calendula.ui.common.rememberCalendarSlideSpec
+import kotlinx.datetime.LocalTime
+import java.util.Calendar
 
 /** The settings sub-screens reached from the hub's category rows. */
 private enum class SettingsSection { Appearance, EventForm, Notifications }
@@ -188,11 +204,15 @@ private fun SettingsHub(
 
 @Composable
 private fun LanguageRow(position: Position) {
+    val context = LocalContext.current
     // Setting a locale recreates the activity; mirror the choice locally so the
     // row updates instantly even before the recreation lands.
-    var current by remember { mutableStateOf(AppLanguage.current()) }
+    var current by remember { mutableStateOf(AppLanguage.currentTag()) }
     var showDialog by remember { mutableStateOf(false) }
 
+    // null = follow the system; the rest are BCP-47 tags from locales_config.xml.
+    val options = remember { listOf<String?>(null) + AppLanguage.supportedTags(context) }
+
     GroupedRow(
         title = stringResource(R.string.settings_language),
         summary = languageLabel(current),
@@ -202,9 +222,9 @@ private fun LanguageRow(position: Position) {
     )
 
     if (showDialog) {
-        OptionPickerDialog(
+        OptionPicker(
             title = stringResource(R.string.settings_language),
-            options = LanguagePref.entries,
+            options = options,
             selected = current,
             label = { languageLabel(it) },
             onSelect = {
@@ -378,7 +398,7 @@ private fun AppearanceScreen(
     }
 
     if (showTheme) {
-        OptionPickerDialog(
+        OptionPicker(
             title = stringResource(R.string.settings_theme),
             options = ThemeMode.entries,
             selected = state.themeMode,
@@ -388,7 +408,7 @@ private fun AppearanceScreen(
         )
     }
     if (showWeekStart) {
-        OptionPickerDialog(
+        OptionPicker(
             title = stringResource(R.string.settings_week_start),
             options = WeekStartPref.entries,
             selected = state.weekStart,
@@ -482,6 +502,12 @@ private fun NotificationsScreen(
         }
     }
 
+    var showDefaultReminder by remember { mutableStateOf(false) }
+    var showAllDayReminder by remember { mutableStateOf(false) }
+    var showAllDayReminderTime by remember { mutableStateOf(false) }
+    var overrideDialog by remember { mutableStateOf<OverrideTarget?>(null) }
+    var expandedCalendars by remember { mutableStateOf(emptySet<Long>()) }
+
     CollapsingScaffold(
         title = stringResource(R.string.settings_section_notifications),
         onBack = onBack,
@@ -489,13 +515,273 @@ private fun NotificationsScreen(
         GroupedRow(
             title = stringResource(R.string.settings_reminders),
             summary = stringResource(R.string.settings_reminders_hint),
-            position = Position.Alone,
+            position = Position.Top,
             trailing = {
                 Switch(checked = state.remindersEnabled, onCheckedChange = toggleReminders)
             },
             onClick = { toggleReminders(!state.remindersEnabled) },
         )
+        GroupedRow(
+            title = stringResource(R.string.settings_default_reminder),
+            summary = reminderChoiceLabel(state.defaultReminderMinutes),
+            position = Position.Middle,
+            onClick = { showDefaultReminder = true },
+        )
+        GroupedRow(
+            title = stringResource(R.string.settings_default_reminder_allday),
+            summary = reminderChoiceLabel(state.defaultAllDayReminderMinutes),
+            position = Position.Middle,
+            onClick = { showAllDayReminder = true },
+        )
+        GroupedRow(
+            title = stringResource(R.string.settings_allday_reminder_time),
+            summary = stringResource(
+                R.string.settings_allday_reminder_time_hint,
+                formatTimeOfDay(context, state.allDayReminderTimeMinutes),
+            ),
+            position = Position.Bottom,
+            onClick = { showAllDayReminderTime = true },
+        )
+
+        // Per-calendar overrides: each writable calendar may keep, drop, or
+        // replace the global default — separately for timed and all-day events.
+        if (state.writableCalendars.isNotEmpty()) {
+            Spacer(Modifier.height(24.dp))
+            Text(
+                text = stringResource(R.string.settings_calendar_reminders_hint),
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.padding(horizontal = 16.dp, vertical = 4.dp),
+            )
+            state.writableCalendars.forEach { calendar ->
+                Spacer(Modifier.height(16.dp))
+                val expanded = calendar.id in expandedCalendars
+                // Calendar card; tapping expands it into a grouped list of three
+                // (the card + the timed and all-day override rows).
+                GroupedRow(
+                    title = calendar.displayName,
+                    position = if (expanded) Position.Top else Position.Alone,
+                    leading = { CalendarColorChip(calendar.color) },
+                    trailing = {
+                        Icon(
+                            imageVector = if (expanded) Icons.Default.ExpandLess else Icons.Default.ExpandMore,
+                            contentDescription = null,
+                            tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                        )
+                    },
+                    onClick = {
+                        expandedCalendars = if (expanded) {
+                            expandedCalendars - calendar.id
+                        } else {
+                            expandedCalendars + calendar.id
+                        }
+                    },
+                )
+                AnimatedVisibility(visible = expanded) {
+                    Column {
+                        val timed = state.perCalendarReminderOverride.choiceFor(calendar.id)
+                        GroupedRow(
+                            title = stringResource(R.string.settings_default_reminder),
+                            summary = calendarOverrideSummary(timed, state.defaultReminderMinutes),
+                            position = Position.Middle,
+                            onClick = { overrideDialog = OverrideTarget(calendar.id, isAllDay = false) },
+                        )
+                        val allDay = state.perCalendarAllDayReminderOverride.choiceFor(calendar.id)
+                        GroupedRow(
+                            title = stringResource(R.string.settings_default_reminder_allday),
+                            summary = calendarOverrideSummary(allDay, state.defaultAllDayReminderMinutes),
+                            position = Position.Bottom,
+                            onClick = { overrideDialog = OverrideTarget(calendar.id, isAllDay = true) },
+                        )
+                    }
+                }
+            }
+        }
+
+        // Delivery reliability: Android's battery optimisation can delay or drop
+        // the calendar provider's reminder broadcast. A soft, optional exemption
+        // (system-settings deep-link, no special permission) improves on-time
+        // delivery; shown as live status, reversible by the user at any time.
+        Spacer(Modifier.height(24.dp))
+        val batteryExempt = rememberBatteryOptimizationExempt()
+        GroupedRow(
+            title = stringResource(R.string.settings_reliable_delivery),
+            summary = if (batteryExempt) {
+                stringResource(R.string.settings_reliable_delivery_exempt)
+            } else {
+                stringResource(R.string.settings_reliable_delivery_hint)
+            },
+            position = Position.Alone,
+            trailing = if (batteryExempt) {
+                {
+                    Icon(
+                        imageVector = Icons.Default.Check,
+                        contentDescription = null,
+                        tint = MaterialTheme.colorScheme.primary,
+                    )
+                }
+            } else {
+                null
+            },
+            onClick = { openBatteryOptimizationSettings(context) },
+        )
     }
+
+    if (showDefaultReminder) {
+        ReminderDefaultPicker(
+            title = stringResource(R.string.settings_default_reminder),
+            presets = REMINDER_PRESETS,
+            selected = state.defaultReminderMinutes.toReminderChoice(),
+            allowInherit = false,
+            onSelect = { viewModel.setDefaultReminderMinutes(it.toMinutesOrNull()) },
+            onDismiss = { showDefaultReminder = false },
+        )
+    }
+    if (showAllDayReminder) {
+        ReminderDefaultPicker(
+            title = stringResource(R.string.settings_default_reminder_allday),
+            presets = ALLDAY_REMINDER_PRESETS,
+            selected = state.defaultAllDayReminderMinutes.toReminderChoice(),
+            allowInherit = false,
+            onSelect = { viewModel.setDefaultAllDayReminderMinutes(it.toMinutesOrNull()) },
+            onDismiss = { showAllDayReminder = false },
+        )
+    }
+    if (showAllDayReminderTime) {
+        TimePickerAlert(
+            initial = LocalTime(
+                state.allDayReminderTimeMinutes / 60,
+                state.allDayReminderTimeMinutes % 60,
+            ),
+            onConfirm = {
+                viewModel.setAllDayReminderTimeMinutes(it.hour * 60 + it.minute)
+                showAllDayReminderTime = false
+            },
+            onDismiss = { showAllDayReminderTime = false },
+        )
+    }
+    overrideDialog?.let { target ->
+        val map = if (target.isAllDay) {
+            state.perCalendarAllDayReminderOverride
+        } else {
+            state.perCalendarReminderOverride
+        }
+        ReminderDefaultPicker(
+            title = stringResource(
+                if (target.isAllDay) {
+                    R.string.settings_default_reminder_allday
+                } else {
+                    R.string.settings_default_reminder
+                },
+            ),
+            presets = if (target.isAllDay) ALLDAY_REMINDER_PRESETS else REMINDER_PRESETS,
+            selected = map.choiceFor(target.calendarId),
+            allowInherit = true,
+            onSelect = {
+                if (target.isAllDay) {
+                    viewModel.setCalendarAllDayReminderOverride(target.calendarId, it)
+                } else {
+                    viewModel.setCalendarReminderOverride(target.calendarId, it)
+                }
+            },
+            onDismiss = { overrideDialog = null },
+        )
+    }
+}
+
+/** Which calendar + event kind a per-calendar reminder-override dialog targets. */
+private data class OverrideTarget(val calendarId: Long, val isAllDay: Boolean)
+
+/** A global default (null = none) as a picker choice for selection highlighting. */
+private fun Int?.toReminderChoice(): CalendarReminderOverride =
+    if (this == null) CalendarReminderOverride.None else CalendarReminderOverride.Minutes(this)
+
+/** A picked choice as global-default minutes (Inherit isn't offered for globals). */
+private fun CalendarReminderOverride.toMinutesOrNull(): Int? =
+    (this as? CalendarReminderOverride.Minutes)?.minutes
+
+/**
+ * Whether Calendula is exempt from battery optimisation, re-read on every
+ * `ON_RESUME` so the row reflects a change the user just made in system
+ * settings without needing to leave and re-enter the screen.
+ */
+@Composable
+private fun rememberBatteryOptimizationExempt(): Boolean {
+    val context = LocalContext.current
+    var exempt by remember { mutableStateOf(isIgnoringBatteryOptimizations(context)) }
+    val lifecycleOwner = LocalLifecycleOwner.current
+    DisposableEffect(lifecycleOwner) {
+        val observer = LifecycleEventObserver { _, event ->
+            if (event == Lifecycle.Event.ON_RESUME) {
+                exempt = isIgnoringBatteryOptimizations(context)
+            }
+        }
+        lifecycleOwner.lifecycle.addObserver(observer)
+        onDispose { lifecycleOwner.lifecycle.removeObserver(observer) }
+    }
+    return exempt
+}
+
+private fun isIgnoringBatteryOptimizations(context: Context): Boolean {
+    val power = context.getSystemService(Context.POWER_SERVICE) as PowerManager
+    return power.isIgnoringBatteryOptimizations(context.packageName)
+}
+
+/**
+ * Take the user straight to Calendula's exemption: the direct
+ * `REQUEST_IGNORE_BATTERY_OPTIMIZATIONS` dialog ("Allow Calendula to ignore
+ * battery optimisation?") rather than the full app list they'd have to scroll.
+ * Falls back to the optimisation list if the OS refuses the direct intent.
+ */
+private fun openBatteryOptimizationSettings(context: Context) {
+    val direct = Intent(
+        Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS,
+        "package:${context.packageName}".toUri(),
+    )
+    if (runCatching { context.startActivity(direct) }.isFailure) {
+        runCatching {
+            context.startActivity(Intent(Settings.ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS))
+        }
+    }
+}
+
+/**
+ * Lead times offered for the all-day default — day-scale, since a "minutes
+ * before midnight" reminder on an all-day event is rarely what's wanted.
+ */
+private val ALLDAY_REMINDER_PRESETS = listOf(0, 1_440, 2_880, 10_080)
+
+/** A minute-of-day formatted in the device's 12/24-hour convention (e.g. "09:00"). */
+private fun formatTimeOfDay(context: Context, minutesOfDay: Int): String {
+    val time = Calendar.getInstance().apply {
+        set(Calendar.HOUR_OF_DAY, minutesOfDay / 60)
+        set(Calendar.MINUTE, minutesOfDay % 60)
+    }.time
+    return DateFormat.getTimeFormat(context).format(time)
+}
+
+/** The stored override for [calendarId], as a picker choice (absent → inherit). */
+private fun Map<Long, Int?>.choiceFor(calendarId: Long): CalendarReminderOverride = when {
+    !containsKey(calendarId) -> CalendarReminderOverride.Inherit
+    this[calendarId] == null -> CalendarReminderOverride.None
+    else -> CalendarReminderOverride.Minutes(this.getValue(calendarId)!!)
+}
+
+/** Label for a global-default choice: null → "None", else the lead time. */
+@Composable
+private fun reminderChoiceLabel(minutes: Int?): String =
+    if (minutes == null) stringResource(R.string.reminder_none) else reminderLeadTimeLabel(minutes)
+
+/** Row summary for a calendar: its override, or the inherited global default. */
+@Composable
+private fun calendarOverrideSummary(
+    choice: CalendarReminderOverride,
+    globalDefault: Int?,
+): String = when (choice) {
+    CalendarReminderOverride.Inherit ->
+        stringResource(R.string.settings_calendar_reminder_inherits, reminderChoiceLabel(globalDefault))
+    CalendarReminderOverride.None -> stringResource(R.string.reminder_none)
+    is CalendarReminderOverride.Minutes -> reminderLeadTimeLabel(choice.minutes)
 }
 
 // ---------------------------------------------------------------------------
@@ -531,38 +817,6 @@ private fun CategoryIcon(icon: ImageVector, accent: ChipAccent) {
     }
 }
 
-/** OptionCard selection dialog — the app's only sanctioned picker style. */
-@Composable
-private fun <T> OptionPickerDialog(
-    title: String,
-    options: List<T>,
-    selected: T,
-    label: @Composable (T) -> String,
-    onSelect: (T) -> Unit,
-    onDismiss: () -> Unit,
-) {
-    AlertDialog(
-        onDismissRequest = onDismiss,
-        title = { Text(title) },
-        text = {
-            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-                options.forEach { option ->
-                    OptionCard(
-                        label = label(option),
-                        onClick = {
-                            onSelect(option)
-                            onDismiss()
-                        },
-                        selected = option == selected,
-                    )
-                }
-            }
-        },
-        confirmButton = {
-            TextButton(onClick = onDismiss) { Text(stringResource(R.string.dialog_cancel)) }
-        },
-    )
-}
 
 private fun openUrl(context: Context, url: String) {
     val intent = Intent(Intent.ACTION_VIEW, url.toUri())
@@ -598,10 +852,5 @@ private fun weekStartLabel(pref: WeekStartPref): String = stringResource(
 )
 
 @Composable
-private fun languageLabel(pref: LanguagePref): String = stringResource(
-    when (pref) {
-        LanguagePref.AUTO -> R.string.settings_language_auto
-        LanguagePref.GERMAN -> R.string.settings_language_german
-        LanguagePref.ENGLISH -> R.string.settings_language_english
-    },
-)
+private fun languageLabel(tag: String?): String =
+    if (tag == null) stringResource(R.string.settings_language_auto) else AppLanguage.displayName(tag)

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsUiState.kt

@@ -3,6 +3,7 @@ package de.jeanlucmakiola.calendula.ui.settings
 import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
 import de.jeanlucmakiola.calendula.data.prefs.ThemeMode
 import de.jeanlucmakiola.calendula.data.prefs.WeekStartPref
+import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventFormField
 
 /**
@@ -20,6 +21,25 @@ data class SettingsUiState(
     val defaultFormFields: Set<EventFormField> = SettingsPrefs.DEFAULT_FORM_FIELDS,
     /** Whether Calendula posts reminder notifications (v1.4). */
     val remindersEnabled: Boolean = true,
+    /**
+     * The default reminder lead time (minutes) prefilled on new timed events;
+     * null = no default reminder. Per-calendar overrides take precedence.
+     */
+    val defaultReminderMinutes: Int? = null,
+    /** The default reminder lead time prefilled on new all-day events; null = none. */
+    val defaultAllDayReminderMinutes: Int? = null,
+    /** Wall-clock time (minutes from midnight) all-day reminders fire at; default 09:00. */
+    val allDayReminderTimeMinutes: Int = SettingsPrefs.DEFAULT_ALLDAY_REMINDER_TIME,
+    /**
+     * Per-calendar overrides of [defaultReminderMinutes] for timed events: a
+     * calendar present in the map overrides the global default (null value = no
+     * reminder); absent = inherit the global default.
+     */
+    val perCalendarReminderOverride: Map<Long, Int?> = emptyMap(),
+    /** Per-calendar overrides of [defaultAllDayReminderMinutes] for all-day events. */
+    val perCalendarAllDayReminderOverride: Map<Long, Int?> = emptyMap(),
+    /** Writable calendars, shown as per-calendar reminder-override rows. */
+    val writableCalendars: List<CalendarSource> = emptyList(),
     /**
      * Whether the event-colour picker is offered on calendars that publish no
      * colour palette (the colour may then not survive their next sync).

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsViewModel.kt

@@ -4,13 +4,19 @@ import android.os.Build
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
+import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
+import de.jeanlucmakiola.calendula.data.prefs.CalendarReminderOverride
 import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
 import de.jeanlucmakiola.calendula.data.prefs.ThemeMode
 import de.jeanlucmakiola.calendula.data.prefs.WeekStartPref
+import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventFormField
+import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 import javax.inject.Inject
@@ -18,14 +24,20 @@ import javax.inject.Inject
 @HiltViewModel
 class SettingsViewModel @Inject constructor(
     private val prefs: SettingsPrefs,
+    repository: CalendarRepository,
 ) : ViewModel() {
 
     private val dynamicColorAvailable = Build.VERSION.SDK_INT >= Build.VERSION_CODES.S
 
+    /** Writable calendars — the only ones that take a per-calendar reminder override. */
+    private val writableCalendars: Flow<List<CalendarSource>> = repository.calendars()
+        .map { calendars -> calendars.filter { it.canModifyContents } }
+        .catch { emit(emptyList()) }
+
     val state: StateFlow<SettingsUiState> =
         combine(
-            // combine() only types up to five flows, so the sixth pref folds
-            // into the assembled state in an outer combine.
+            // combine() types up to five flows, so the prefs split into two
+            // groups that fold together in the outer combine.
             combine(
                 prefs.themeMode,
                 prefs.dynamicColor,
@@ -42,15 +54,50 @@ class SettingsViewModel @Inject constructor(
                     remindersEnabled = reminders,
                 )
             },
-            prefs.allowColorOnUnsupportedCalendars,
-        ) { base, allowColor ->
-            base.copy(allowColorOnUnsupportedCalendars = allowColor)
+            combine(
+                prefs.allowColorOnUnsupportedCalendars,
+                prefs.defaultReminderMinutes,
+                prefs.defaultAllDayReminderMinutes,
+                prefs.allDayReminderTimeMinutes,
+            ) { allowColor, defaultReminder, allDayReminder, allDayReminderTime ->
+                ReminderDefaults(allowColor, defaultReminder, allDayReminder, allDayReminderTime)
+            },
+            combine(
+                prefs.perCalendarReminderOverride,
+                prefs.perCalendarAllDayReminderOverride,
+                writableCalendars,
+            ) { overrides, allDayOverrides, calendars ->
+                ReminderOverrides(overrides, allDayOverrides, calendars)
+            },
+        ) { base, defaults, overrides ->
+            base.copy(
+                allowColorOnUnsupportedCalendars = defaults.allowColor,
+                defaultReminderMinutes = defaults.defaultReminder,
+                defaultAllDayReminderMinutes = defaults.allDayReminder,
+                allDayReminderTimeMinutes = defaults.allDayReminderTime,
+                perCalendarReminderOverride = overrides.timed,
+                perCalendarAllDayReminderOverride = overrides.allDay,
+                writableCalendars = overrides.calendars,
+            )
         }.stateIn(
             scope = viewModelScope,
             started = SharingStarted.WhileSubscribed(5_000L),
             initialValue = SettingsUiState(dynamicColorAvailable = dynamicColorAvailable),
         )
 
+    private data class ReminderDefaults(
+        val allowColor: Boolean,
+        val defaultReminder: Int?,
+        val allDayReminder: Int?,
+        val allDayReminderTime: Int,
+    )
+
+    private data class ReminderOverrides(
+        val timed: Map<Long, Int?>,
+        val allDay: Map<Long, Int?>,
+        val calendars: List<CalendarSource>,
+    )
+
     fun setThemeMode(mode: ThemeMode) {
         viewModelScope.launch { prefs.setThemeMode(mode) }
     }
@@ -71,6 +118,26 @@ class SettingsViewModel @Inject constructor(
         viewModelScope.launch { prefs.setRemindersEnabled(enabled) }
     }
 
+    fun setDefaultReminderMinutes(minutes: Int?) {
+        viewModelScope.launch { prefs.setDefaultReminderMinutes(minutes) }
+    }
+
+    fun setDefaultAllDayReminderMinutes(minutes: Int?) {
+        viewModelScope.launch { prefs.setDefaultAllDayReminderMinutes(minutes) }
+    }
+
+    fun setAllDayReminderTimeMinutes(minutesOfDay: Int) {
+        viewModelScope.launch { prefs.setAllDayReminderTimeMinutes(minutesOfDay) }
+    }
+
+    fun setCalendarReminderOverride(calendarId: Long, override: CalendarReminderOverride) {
+        viewModelScope.launch { prefs.setCalendarReminderOverride(calendarId, override) }
+    }
+
+    fun setCalendarAllDayReminderOverride(calendarId: Long, override: CalendarReminderOverride) {
+        viewModelScope.launch { prefs.setCalendarAllDayReminderOverride(calendarId, override) }
+    }
+
     fun setAllowColorOnUnsupportedCalendars(enabled: Boolean) {
         viewModelScope.launch { prefs.setAllowColorOnUnsupportedCalendars(enabled) }
     }

app/src/main/java/de/jeanlucmakiola/calendula/ui/week/WeekViewModel.kt

@@ -181,6 +181,18 @@ internal fun weekRange(start: LocalDate, zone: TimeZone): ClosedRange<Instant> {
 
 /** True if this event overlaps the calendar [day] in [zone] (any portion). */
 internal fun EventInstance.coversDay(day: LocalDate, zone: TimeZone): Boolean {
+    if (isAllDay) {
+        // All-day events live at UTC midnights with an exclusive end. Compare
+        // calendar dates in UTC and step the exclusive end back to the last
+        // covered day (mirroring the detail/edit views), so a one-day event
+        // covers exactly its single date. Slicing the day in the device zone
+        // would push the exclusive end a few hours into the next local day
+        // east of UTC, making the event leak onto day + 1.
+        val startDate = start.toLocalDateTime(TimeZone.UTC).date
+        val endExclusive = end.toLocalDateTime(TimeZone.UTC).date
+        val lastDay = maxOf(startDate, endExclusive.minus(1, DateTimeUnit.DAY))
+        return day in startDate..lastDay
+    }
     val dayStart = day.atStartOfDayIn(zone)
     val dayEnd = day.plus(1, DateTimeUnit.DAY).atStartOfDayIn(zone)
     return start < dayEnd && end > dayStart

app/src/main/res/values-de/strings.xml

@@ -47,6 +47,9 @@
     <string name="event_detail_back">Zurück</string>
     <string name="event_detail_edit">Bearbeiten</string>
     <string name="event_detail_delete">Löschen</string>
+    <string name="event_detail_share">Teilen</string>
+    <string name="event_share_chooser_title">Termin teilen</string>
+    <string name="event_share_failed">Termin konnte nicht geteilt werden.</string>
     <string name="event_delete_title">Termin löschen?</string>
     <string name="event_delete_body">Der Termin wird aus deinem Kalender und von allen synchronisierten Geräten entfernt.</string>
     <string name="event_delete_recurring_title">Wiederkehrenden Termin löschen</string>
@@ -248,14 +251,26 @@
     <string name="settings_section_notifications">Benachrichtigungen</string>
     <string name="settings_reminders">Termin-Erinnerungen</string>
     <string name="settings_reminders_hint">Erinnerungen doppelt? Eine andere Kalender-App zeigt sie ebenfalls — schalte sie in einer der beiden ab.</string>
+    <string name="settings_default_reminder">Standard-Erinnerung</string>
+    <string name="settings_default_reminder_allday">Ganztägige Termine</string>
+    <string name="settings_allday_reminder_time">Uhrzeit für ganztägige Erinnerungen</string>
+    <string name="settings_allday_reminder_time_hint">Erinnerungen für ganztägige Termine werden um %1$s ausgelöst</string>
+    <string name="reminder_none">Keine</string>
+    <string name="reminder_use_default">Standard-Erinnerung verwenden</string>
+    <string name="reminder_custom_amount">Anzahl</string>
+    <string name="reminder_custom_with_value">Benutzerdefiniert (%1$s)</string>
+    <string name="reminder_custom_set">Übernehmen</string>
+    <string name="settings_calendar_reminders_hint">Standard pro Kalender überschreiben — getrennt für Termine mit Uhrzeit und ganztägige Termine. Ein Kalender kann den Standard übernehmen, weglassen oder einen eigenen festlegen.</string>
+    <string name="settings_calendar_reminder_inherits">Standard (%1$s)</string>
+    <string name="settings_reliable_delivery">Zuverlässige Zustellung</string>
+    <string name="settings_reliable_delivery_hint">Android verzögert Erinnerungen womöglich, um Akku zu sparen. Nimm Calendula aus, damit sie pünktlich ankommen.</string>
+    <string name="settings_reliable_delivery_exempt">Von der Akku-Optimierung ausgenommen — Erinnerungen kommen pünktlich.</string>
     <string name="settings_section_calendars">Kalender</string>
     <string name="settings_manage_calendars">Kalender verwalten</string>
     <string name="settings_manage_calendars_hint">Lokale Kalender anlegen, synchronisierte verwalten</string>
     <string name="settings_section_language">Sprache</string>
     <string name="settings_language">App-Sprache</string>
     <string name="settings_language_auto">Systemstandard</string>
-    <string name="settings_language_german">Deutsch</string>
-    <string name="settings_language_english">English</string>
     <!-- Hub category subtitles -->
     <string name="settings_appearance_subtitle">Design, dynamische Farben, Wochenstart</string>
     <string name="settings_event_form_subtitle">Standardfelder für neue Termine</string>
@@ -285,4 +300,41 @@
     <string name="calendars_delete_confirm_title">Kalender löschen?</string>
     <string name="calendars_delete_confirm_message">\"%1$s\" und alle zugehörigen Termine werden dauerhaft von diesem Gerät entfernt.</string>
     <string name="calendars_write_error">Änderung konnte nicht gespeichert werden.</string>
+    <!-- Backup (whole-calendar .ics export) -->
+    <string name="calendars_backup_header">Sicherung</string>
+    <string name="calendars_backup_hint">Lokale Kalender werden nirgends synchronisiert – exportiere sie als .ics-Datei, um eine Kopie zu behalten.</string>
+    <string name="calendars_backup_action">Als .ics-Datei exportieren</string>
+    <string name="calendars_backup_failed">Sicherung konnte nicht exportiert werden.</string>
+    <plurals name="calendars_backup_done">
+        <item quantity="one">%d Termin exportiert.</item>
+        <item quantity="other">%d Termine exportiert.</item>
+    </plurals>
+    <!-- Import (.ics) -->
+    <string name="import_title">Termine importieren</string>
+    <string name="import_target_header">Zu Kalender hinzufügen</string>
+    <string name="import_empty">In dieser Datei wurden keine Termine gefunden.</string>
+    <string name="import_failed">Datei konnte nicht gelesen werden.</string>
+    <string name="import_no_calendar">Kein beschreibbarer Kalender zum Importieren. Lege zuerst einen lokalen Kalender an.</string>
+    <string name="import_done_title">Import abgeschlossen</string>
+    <string name="import_close">Schließen</string>
+    <string name="import_warning_recurrence">Einige geänderte Einzeltermine wiederkehrender Termine wurden übersprungen.</string>
+    <string name="import_warning_no_start">Ein Termin ohne Startzeit wurde übersprungen.</string>
+    <string name="import_warning_attendees">Gästelisten wurden nicht importiert.</string>
+    <string name="import_warning_timezone">Eine unbekannte Zeitzone wurde durch die deines Geräts ersetzt.</string>
+    <plurals name="import_event_count">
+        <item quantity="one">%d Termin in dieser Datei.</item>
+        <item quantity="other">%d Termine in dieser Datei.</item>
+    </plurals>
+    <plurals name="import_action">
+        <item quantity="one">%d Termin importieren</item>
+        <item quantity="other">%d Termine importieren</item>
+    </plurals>
+    <plurals name="import_done_imported">
+        <item quantity="one">%d Termin importiert.</item>
+        <item quantity="other">%d Termine importiert.</item>
+    </plurals>
+    <plurals name="import_done_skipped">
+        <item quantity="one">%d bereits in diesem Kalender übersprungen.</item>
+        <item quantity="other">%d bereits in diesem Kalender übersprungen.</item>
+    </plurals>
 </resources>

app/src/main/res/values-night/colors.xml

@@ -0,0 +1,6 @@
+<resources>
+    <!-- Dark-scheme window backdrop, matching the Compose dark background/surface
+         (#101316) so activity recreation (e.g. language switch) doesn't flash a
+         lighter grey. See values/colors.xml. -->
+    <color name="window_background">#FF101316</color>
+</resources>

app/src/main/res/values/colors.xml

@@ -3,4 +3,8 @@
     <color name="seed">#FF5C6B7A</color>
     <!-- Adaptive icon background -->
     <color name="ic_launcher_background">#FF5C6B7A</color>
+    <!-- Window backdrop shown during activity recreation (e.g. on a language
+         switch). Matches the Compose light scheme background/surface so the
+         recreation is seamless; overridden for dark in values-night. -->
+    <color name="window_background">#FFFBFCFE</color>
 </resources>

app/src/main/res/values/strings.xml

@@ -48,6 +48,9 @@
     <string name="event_detail_back">Back</string>
     <string name="event_detail_edit">Edit</string>
     <string name="event_detail_delete">Delete</string>
+    <string name="event_detail_share">Share</string>
+    <string name="event_share_chooser_title">Share event</string>
+    <string name="event_share_failed">Couldn\'t share this event.</string>
     <string name="event_delete_title">Delete event?</string>
     <string name="event_delete_body">The event is removed from your calendar and from every device it syncs to.</string>
     <string name="event_delete_recurring_title">Delete recurring event</string>
@@ -245,14 +248,26 @@
     <string name="settings_section_notifications">Notifications</string>
     <string name="settings_reminders">Event reminders</string>
     <string name="settings_reminders_hint">Seeing reminders twice? Another calendar app is posting them too — turn them off in one of the two.</string>
+    <string name="settings_default_reminder">Default reminder</string>
+    <string name="settings_default_reminder_allday">All-day events</string>
+    <string name="settings_allday_reminder_time">All-day reminder time</string>
+    <string name="settings_allday_reminder_time_hint">Reminders for all-day events fire at %1$s</string>
+    <string name="reminder_none">None</string>
+    <string name="reminder_use_default">Use default reminder</string>
+    <string name="reminder_custom_amount">Amount</string>
+    <string name="reminder_custom_with_value">Custom (%1$s)</string>
+    <string name="reminder_custom_set">Set</string>
+    <string name="settings_calendar_reminders_hint">Override the default per calendar — separately for timed and all-day events. A calendar can keep the default, drop it, or set its own.</string>
+    <string name="settings_calendar_reminder_inherits">Default (%1$s)</string>
+    <string name="settings_reliable_delivery">Reliable delivery</string>
+    <string name="settings_reliable_delivery_hint">Android may delay reminders to save battery. Exempt Calendula so they arrive on time.</string>
+    <string name="settings_reliable_delivery_exempt">Exempt from battery optimisation — reminders arrive on time.</string>
     <string name="settings_section_calendars">Calendars</string>
     <string name="settings_manage_calendars">Manage calendars</string>
     <string name="settings_manage_calendars_hint">Create local calendars; manage synced ones</string>
     <string name="settings_section_language">Language</string>
     <string name="settings_language">App language</string>
     <string name="settings_language_auto">System default</string>
-    <string name="settings_language_german">Deutsch</string>
-    <string name="settings_language_english">English</string>
     <!-- Hub category subtitles -->
     <string name="settings_appearance_subtitle">Theme, dynamic colour, week start</string>
     <string name="settings_event_form_subtitle">Default fields for new events</string>
@@ -282,6 +297,43 @@
     <string name="calendars_delete_confirm_title">Delete calendar?</string>
     <string name="calendars_delete_confirm_message">\"%1$s\" and all of its events will be permanently removed from this device.</string>
     <string name="calendars_write_error">Couldn\'t save the change.</string>
+    <!-- Backup (whole-calendar .ics export) -->
+    <string name="calendars_backup_header">Backup</string>
+    <string name="calendars_backup_hint">Local calendars aren\'t synced anywhere, so export them to an .ics file to keep a copy.</string>
+    <string name="calendars_backup_action">Export as .ics file</string>
+    <string name="calendars_backup_failed">Couldn\'t export the backup.</string>
+    <plurals name="calendars_backup_done">
+        <item quantity="one">Exported %d event.</item>
+        <item quantity="other">Exported %d events.</item>
+    </plurals>
+    <!-- Import (.ics) -->
+    <string name="import_title">Import events</string>
+    <string name="import_target_header">Add to calendar</string>
+    <string name="import_empty">No events found in this file.</string>
+    <string name="import_failed">Couldn\'t read this file.</string>
+    <string name="import_no_calendar">No writable calendar to import into. Create a local calendar first.</string>
+    <string name="import_done_title">Import complete</string>
+    <string name="import_close">Close</string>
+    <string name="import_warning_recurrence">Some changed occurrences of recurring events were skipped.</string>
+    <string name="import_warning_no_start">An event without a start time was skipped.</string>
+    <string name="import_warning_attendees">Guest lists weren\'t imported.</string>
+    <string name="import_warning_timezone">An unknown time zone fell back to your device\'s.</string>
+    <plurals name="import_event_count">
+        <item quantity="one">%d event in this file.</item>
+        <item quantity="other">%d events in this file.</item>
+    </plurals>
+    <plurals name="import_action">
+        <item quantity="one">Import %d event</item>
+        <item quantity="other">Import %d events</item>
+    </plurals>
+    <plurals name="import_done_imported">
+        <item quantity="one">Imported %d event.</item>
+        <item quantity="other">Imported %d events.</item>
+    </plurals>
+    <plurals name="import_done_skipped">
+        <item quantity="one">Skipped %d already in this calendar.</item>
+        <item quantity="other">Skipped %d already in this calendar.</item>
+    </plurals>
     <!-- Launcher long-press shortcuts -->
     <string name="shortcut_new_event_short">New event</string>
     <string name="shortcut_new_event_long">Create a new event</string>

app/src/main/res/values/themes.xml

@@ -1,5 +1,10 @@
 <resources xmlns:tools="http://schemas.android.com/tools">
-    <style name="Theme.Calendula" parent="android:Theme.Material.Light.NoActionBar">
+    <!-- AppCompat (DayNight) parent so MainActivity can be an AppCompatActivity,
+         which is required for AppCompatDelegate.setApplicationLocales (the in-app
+         language picker) to sync to the system. Actual colours are driven by the
+         Compose theme; this is essentially the launch/backdrop theme. -->
+    <style name="Theme.Calendula" parent="Theme.AppCompat.DayNight.NoActionBar">
+        <item name="android:windowBackground">@color/window_background</item>
         <item name="android:statusBarColor">@android:color/transparent</item>
         <item name="android:navigationBarColor">@android:color/transparent</item>
         <item name="android:windowLightStatusBar">true</item>

app/src/main/res/xml/file_paths.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Exposes the cache subdirectory where IcsExporter stages files for sharing. -->
+<paths>
+    <cache-path
+        name="shared_ics"
+        path="shared_ics/" />
+</paths>

app/src/main/res/xml/locales_config.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+    The languages Calendula ships translations for. This is the single source of
+    truth: each entry must have a matching res/values-<tag>/strings.xml, and is
+    surfaced automatically in both the in-app language picker (parsed at runtime
+    by AppLanguage) and the system per-app language settings (Android 13+, via
+    android:localeConfig in the manifest). To add a community translation, drop
+    in the values-<tag> folder and add one <locale> line here.
+-->
+<locale-config xmlns:android="http://schemas.android.com/apk/res/android">
+    <locale android:name="en" />
+    <locale android:name="de" />
+</locale-config>

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/AllDayReminderEncodingTest.kt

@@ -0,0 +1,97 @@
+package de.jeanlucmakiola.calendula.data.calendar
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+import java.time.LocalDate
+import java.time.LocalTime
+import java.time.ZoneId
+import java.time.ZoneOffset
+
+class AllDayReminderEncodingTest {
+
+    private val berlin: ZoneId = ZoneId.of("Europe/Berlin")
+    private val nineAm = 9 * 60
+    private val summer = LocalDate.of(2026, 6, 20) // CEST, UTC+2
+    private val winter = LocalDate.of(2026, 1, 20) // CET, UTC+1
+
+    /** The instant the provider would actually fire: DTSTART(UTC midnight) − raw. */
+    private fun actualFire(rawMinutes: Int, startDate: LocalDate): Long =
+        startDate.atStartOfDay(ZoneOffset.UTC).toInstant().toEpochMilli() -
+            rawMinutes * 60_000L
+
+    /** The wall-clock instant we intend: [time] local, [daysBefore] days before [startDate]. */
+    private fun intendedFire(startDate: LocalDate, daysBefore: Int, timeMinutes: Int): Long =
+        startDate.minusDays(daysBefore.toLong())
+            .atTime(LocalTime.of(timeMinutes / 60, timeMinutes % 60))
+            .atZone(berlin).toInstant().toEpochMilli()
+
+    @Test
+    fun `one day before at 9am fires at 9am local the day before (summer)`() {
+        val raw = toProviderAllDayMinutes(1_440, summer, berlin, nineAm)
+        assertThat(actualFire(raw, summer)).isEqualTo(intendedFire(summer, 1, nineAm))
+        // 09:00 CEST is 07:00Z, 7h later than the bare midnight offset: 1440 − 420.
+        assertThat(raw).isEqualTo(1_020)
+    }
+
+    @Test
+    fun `one day before at 9am fires at 9am local the day before (winter)`() {
+        val raw = toProviderAllDayMinutes(1_440, winter, berlin, nineAm)
+        assertThat(actualFire(raw, winter)).isEqualTo(intendedFire(winter, 1, nineAm))
+        // 09:00 CET is 08:00Z, 8h later than midnight: 1440 − 480.
+        assertThat(raw).isEqualTo(960)
+    }
+
+    @Test
+    fun `at time of event encodes a negative offset firing 9am on the day (summer)`() {
+        val raw = toProviderAllDayMinutes(0, summer, berlin, nineAm)
+        assertThat(raw).isLessThan(0) // fires after DTSTART; must not be clamped
+        assertThat(actualFire(raw, summer)).isEqualTo(intendedFire(summer, 0, nineAm))
+    }
+
+    @Test
+    fun `round-trips for whole-day lead times across both seasons`() {
+        for (date in listOf(summer, winter)) {
+            for (time in listOf(0, nineAm, 20 * 60)) {
+                for (semantic in listOf(0, 1_440, 2_880, 10_080)) {
+                    val raw = toProviderAllDayMinutes(semantic, date, berlin, time)
+                    assertThat(fromProviderAllDayMinutes(raw, date, berlin)).isEqualTo(semantic)
+                }
+            }
+        }
+    }
+
+    @Test
+    fun `pre-feature rows (raw multiple of 1440) still decode to whole days`() {
+        // Reminders written before this feature stored raw N*1440 (fired at UTC
+        // midnight). They must still read back as "N days before".
+        assertThat(fromProviderAllDayMinutes(1_440, summer, berlin)).isEqualTo(1_440)
+        assertThat(fromProviderAllDayMinutes(1_440, winter, berlin)).isEqualTo(1_440)
+        assertThat(fromProviderAllDayMinutes(2_880, summer, berlin)).isEqualTo(2_880)
+    }
+
+    @Test
+    fun `decoding is independent of the time-of-day used to encode`() {
+        val atNine = toProviderAllDayMinutes(1_440, summer, berlin, nineAm)
+        val atEight = toProviderAllDayMinutes(1_440, summer, berlin, 8 * 60)
+        assertThat(atNine).isNotEqualTo(atEight)
+        assertThat(fromProviderAllDayMinutes(atNine, summer, berlin)).isEqualTo(1_440)
+        assertThat(fromProviderAllDayMinutes(atEight, summer, berlin)).isEqualTo(1_440)
+    }
+
+    @Test
+    fun `negative semantic minutes (provider-default sentinel) pass through`() {
+        assertThat(toProviderAllDayMinutes(-1, summer, berlin, nineAm)).isEqualTo(-1)
+    }
+
+    @Test
+    fun `a winter-anchored offset drifts one hour on a summer occurrence`() {
+        // Known limitation: one fixed MINUTES per series can't track DST. An
+        // offset tuned for a CET anchor fires an hour off once the series crosses
+        // into CEST. Bounded to ±1h; documented, not fixed.
+        val raw = toProviderAllDayMinutes(1_440, winter, berlin, nineAm)
+        val summerOccurrence = LocalDate.of(2026, 7, 20)
+        val fire = actualFire(raw, summerOccurrence).let(java.time.Instant::ofEpochMilli)
+            .atZone(berlin).toLocalTime()
+        assertThat(fire).isEqualTo(LocalTime.of(10, 0)) // 09:00 intended, +1h in CEST
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImplTest.kt

@@ -6,6 +6,7 @@ import androidx.datastore.preferences.core.Preferences
 import app.cash.turbine.test
 import com.google.common.truth.Truth.assertThat
 import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
+import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventForm
@@ -28,6 +29,13 @@ class CalendarRepositoryImplTest {
     private fun newPrefs(tempDir: Path): CalendarPrefs =
         CalendarPrefs(newDataStore(tempDir))
 
+    private fun newSettings(tempDir: Path): SettingsPrefs =
+        SettingsPrefs(
+            PreferenceDataStoreFactory.create(
+                produceFile = { tempDir.resolve("repo_test_settings.preferences_pb").toFile() },
+            ),
+        )
+
     private fun newDataStore(tempDir: Path): DataStore<Preferences> =
         PreferenceDataStoreFactory.create(
             produceFile = { tempDir.resolve("repo_test_prefs.preferences_pb").toFile() },
@@ -53,7 +61,7 @@ class CalendarRepositoryImplTest {
         val fake = FakeCalendarDataSource().apply {
             calendarsResult = listOf(makeCal(1L), makeCal(2L))
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), UnconfinedTestDispatcher(testScheduler))
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
 
         repo.calendars().test {
             val first = awaitItem()
@@ -67,7 +75,7 @@ class CalendarRepositoryImplTest {
         val fake = FakeCalendarDataSource().apply {
             calendarsResult = listOf(makeCal(1L))
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), UnconfinedTestDispatcher(testScheduler))
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
 
         repo.calendars().test {
             assertThat(awaitItem().map { it.id }).containsExactly(1L)
@@ -91,7 +99,7 @@ class CalendarRepositoryImplTest {
                 listOf(makeEvent(10L))
             }
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), UnconfinedTestDispatcher(testScheduler))
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
 
         val range = Instant.fromEpochMilliseconds(1_000L)..Instant.fromEpochMilliseconds(2_000L)
         repo.instances(range).test {
@@ -107,7 +115,7 @@ class CalendarRepositoryImplTest {
         val fake = FakeCalendarDataSource().apply {
             instancesResult = {_, _ -> listOf(makeEvent(10L, "Good")) }
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), UnconfinedTestDispatcher(testScheduler))
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
 
         val range = Instant.fromEpochMilliseconds(0)..Instant.fromEpochMilliseconds(10_000L)
         repo.instances(range).test {
@@ -129,7 +137,7 @@ class CalendarRepositoryImplTest {
                 )
             }
         }
-        val repo = CalendarRepositoryImpl(fake, prefs, UnconfinedTestDispatcher(testScheduler))
+        val repo = CalendarRepositoryImpl(fake, prefs, newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
 
         val range = Instant.fromEpochMilliseconds(0)..Instant.fromEpochMilliseconds(10_000L)
         repo.instances(range).test {
@@ -149,7 +157,7 @@ class CalendarRepositoryImplTest {
                 )
             }
         }
-        val repo = CalendarRepositoryImpl(fake, prefs, UnconfinedTestDispatcher(testScheduler))
+        val repo = CalendarRepositoryImpl(fake, prefs, newSettings(tempDir), UnconfinedTestDispatcher(testScheduler))
 
         val range = Instant.fromEpochMilliseconds(0)..Instant.fromEpochMilliseconds(10_000L)
         repo.instances(range).test {
@@ -165,7 +173,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `createEvent delegates and returns the new id`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource().apply { nextInsertId = 77L }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
         val form = EventForm(
             calendarId = 1L,
             title = "Stand-up",
@@ -179,12 +187,32 @@ class CalendarRepositoryImplTest {
         assertThat(fake.insertedForms).containsExactly(form)
     }
 
+    @Test
+    fun `createEvent passes the configured all-day reminder time to the data source`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        val fake = FakeCalendarDataSource()
+        val settings = newSettings(tempDir)
+        settings.setAllDayReminderTimeMinutes(8 * 60) // 08:00
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), settings, Dispatchers.Unconfined)
+        val form = EventForm(
+            calendarId = 1L,
+            isAllDay = true,
+            start = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(0, 0)),
+            end = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(0, 0)),
+        )
+
+        repo.createEvent(form)
+
+        assertThat(fake.allDayReminderTimes).containsExactly(480)
+    }
+
     @Test
     fun `createEvent propagates write failures`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource().apply {
             writeError = WriteFailedException("insert event")
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
         val form = EventForm(
             calendarId = 1L,
             start = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(9, 0)),
@@ -202,7 +230,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `updateEvent forwards id and both forms`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource()
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
         val original = EventForm(
             calendarId = 1L,
             title = "Stand-up",
@@ -221,7 +249,7 @@ class CalendarRepositoryImplTest {
         val fake = FakeCalendarDataSource().apply {
             writeError = WriteFailedException("update event id=42")
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
         val form = EventForm(
             calendarId = 1L,
             start = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(9, 0)),
@@ -239,7 +267,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `deleteEvent delegates to the data source`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource()
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         repo.deleteEvent(eventId = 42L)
 
@@ -250,7 +278,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `deleteOccurrence forwards event id and begin time`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource()
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         repo.deleteOccurrence(eventId = 42L, beginMillis = 1_000L)
 
@@ -261,7 +289,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `deleteEventFromOccurrence forwards event id and begin time`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource()
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         repo.deleteEventFromOccurrence(eventId = 42L, beginMillis = 1_000L)
 
@@ -273,7 +301,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `updateOccurrence forwards target and form, returns the exception id`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource().apply { nextInsertId = 88L }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
         val form = EventForm(
             calendarId = 1L,
             title = "Moved",
@@ -291,7 +319,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `updateEventFromOccurrence forwards target and forms, returns the new id`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource().apply { nextInsertId = 99L }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
         val original = EventForm(
             calendarId = 1L,
             title = "Weekly",
@@ -318,7 +346,7 @@ class CalendarRepositoryImplTest {
         val fake = FakeCalendarDataSource().apply {
             writeError = WriteFailedException("delete event id=42")
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         try {
             repo.deleteEvent(eventId = 42L)
@@ -331,7 +359,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `createLocalCalendar delegates and returns the new id`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource().apply { nextCalendarId = 501L }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         val id = repo.createLocalCalendar(
             displayName = "Home",
@@ -348,7 +376,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `updateCalendar forwards id, name, color and description`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource()
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         repo.updateCalendar(
             id = 5L,
@@ -365,7 +393,7 @@ class CalendarRepositoryImplTest {
     @Test
     fun `deleteCalendar delegates to the data source`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource()
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         repo.deleteCalendar(id = 7L)
 
@@ -377,7 +405,7 @@ class CalendarRepositoryImplTest {
         val fake = FakeCalendarDataSource().apply {
             writeError = WriteFailedException("create local calendar 'Home'")
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         try {
             repo.createLocalCalendar(displayName = "Home", color = 0, description = null)
@@ -392,7 +420,7 @@ class CalendarRepositoryImplTest {
         val fake = FakeCalendarDataSource().apply {
             eventDetailResult = { null }
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         try {
             repo.eventDetail(eventId = 999L)
@@ -411,10 +439,41 @@ class CalendarRepositoryImplTest {
                 if (id == 7L) listOf(EventColorOption("5", 0xFF33B679.toInt())) else emptyList()
             }
         }
-        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
 
         assertThat(repo.eventColorPalette(7L))
             .containsExactly(EventColorOption("5", 0xFF33B679.toInt()))
         assertThat(repo.eventColorPalette(8L)).isEmpty()
     }
+
+    @Test
+    fun `importEvents skips events whose UID already exists and inserts the rest`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        val fake = FakeCalendarDataSource().apply {
+            existingUidsResult = setOf("dup@x")
+        }
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), newSettings(tempDir), Dispatchers.Unconfined)
+        val events = listOf(
+            parsedEvent("dup@x"), // already present → skipped
+            parsedEvent("new@x"), // inserted
+            parsedEvent(null), // no UID → always inserted
+        )
+
+        val summary = repo.importEvents(targetCalendarId = 3L, events = events)
+
+        assertThat(summary.imported).isEqualTo(2)
+        assertThat(summary.skippedDuplicate).isEqualTo(1)
+        assertThat(fake.importedEvents.map { it.first.uid }).containsExactly("new@x", null)
+        assertThat(fake.importedEvents.map { it.second }).containsExactly(3L, 3L)
+    }
+
+    private fun parsedEvent(uid: String?) = de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent(
+        uid = uid,
+        summary = "E",
+        start = Instant.fromEpochMilliseconds(1_000_000_000L),
+        end = Instant.fromEpochMilliseconds(1_000_003_600L),
+        isAllDay = false,
+        zoneId = "UTC",
+    )
 }

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/FakeCalendarDataSource.kt

@@ -5,6 +5,8 @@ import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventDetail
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
+import de.jeanlucmakiola.calendula.domain.ics.IcsEvent
+import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
 
 /**
  * Test-only fake. Tunable via the three `var` properties; `tick()` simulates
@@ -16,6 +18,9 @@ internal class FakeCalendarDataSource : CalendarDataSource {
     var instancesResult: (Long, Long) -> List<EventInstance> = { _, _ -> emptyList() }
     var eventDetailResult: (Long) -> EventDetail? = { null }
     var eventColorPaletteResult: (Long) -> List<EventColorOption> = { emptyList() }
+    var exportableEventsResult: List<IcsEvent> = emptyList()
+    /** UIDs the target calendar already holds, for import dedup. */
+    var existingUidsResult: Set<String> = emptySet()
     /** Set to make the next write call throw. */
     var writeError: Exception? = null
     /** Id returned by the next [insertEvent]. */
@@ -49,6 +54,18 @@ internal class FakeCalendarDataSource : CalendarDataSource {
     override fun eventDetail(eventId: Long): EventDetail? = eventDetailResult(eventId)
     override fun eventColorPalette(calendarId: Long): List<EventColorOption> =
         eventColorPaletteResult(calendarId)
+    override fun exportableEvents(): List<IcsEvent> = exportableEventsResult
+
+    override fun existingUids(calendarId: Long): Set<String> = existingUidsResult
+
+    /** (event, targetCalendarId) pairs passed to [insertImportedEvent]. */
+    val importedEvents = mutableListOf<Pair<ParsedIcsEvent, Long>>()
+
+    override fun insertImportedEvent(event: ParsedIcsEvent, calendarId: Long): Long {
+        writeError?.let { throw it }
+        importedEvents += event to calendarId
+        return nextInsertId
+    }
 
     override fun createLocalCalendar(displayName: String, color: Int, description: String?): Long {
         writeError?.let { throw it }
@@ -66,20 +83,36 @@ internal class FakeCalendarDataSource : CalendarDataSource {
         deletedCalendarIds += id
     }
 
-    override fun insertEvent(form: EventForm): Long {
+    /** All-day reminder fire-time minute-of-day passed into the last write. */
+    val allDayReminderTimes = mutableListOf<Int>()
+
+    override fun insertEvent(form: EventForm, allDayReminderTimeMinutes: Int): Long {
         writeError?.let { throw it }
         insertedForms += form
+        allDayReminderTimes += allDayReminderTimeMinutes
         return nextInsertId
     }
 
-    override fun updateEvent(eventId: Long, original: EventForm, updated: EventForm) {
+    override fun updateEvent(
+        eventId: Long,
+        original: EventForm,
+        updated: EventForm,
+        allDayReminderTimeMinutes: Int,
+    ) {
         writeError?.let { throw it }
         updatedEvents += Triple(eventId, original, updated)
+        allDayReminderTimes += allDayReminderTimeMinutes
     }
 
-    override fun updateOccurrence(eventId: Long, beginMillis: Long, form: EventForm): Long {
+    override fun updateOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        form: EventForm,
+        allDayReminderTimeMinutes: Int,
+    ): Long {
         writeError?.let { throw it }
         updatedOccurrences += Triple(eventId, beginMillis, form)
+        allDayReminderTimes += allDayReminderTimeMinutes
         return nextInsertId
     }
 
@@ -88,9 +121,11 @@ internal class FakeCalendarDataSource : CalendarDataSource {
         beginMillis: Long,
         original: EventForm,
         updated: EventForm,
+        allDayReminderTimeMinutes: Int,
     ): Long {
         writeError?.let { throw it }
         updatedFromOccurrences += Triple(eventId, beginMillis, updated)
+        allDayReminderTimes += allDayReminderTimeMinutes
         return nextInsertId
     }
 

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/IcsExportMapperTest.kt

@@ -0,0 +1,70 @@
+package de.jeanlucmakiola.calendula.data.calendar
+
+import android.provider.CalendarContract
+import com.google.common.truth.Truth.assertThat
+import de.jeanlucmakiola.calendula.domain.EventStatus
+import org.junit.jupiter.api.Test
+
+class IcsExportMapperTest {
+
+    @Test
+    fun `timed one-off row maps with its DTEND and kept UID`() {
+        val reader = MapColumnReader(
+            EventExportProjection.IDX_ID to 42L,
+            EventExportProjection.IDX_UID to "abc@host",
+            EventExportProjection.IDX_TITLE to "Standup",
+            EventExportProjection.IDX_DTSTART to 1_000_000L,
+            EventExportProjection.IDX_DTEND to 1_900_000L,
+            EventExportProjection.IDX_ALL_DAY to 0,
+            EventExportProjection.IDX_EVENT_TIMEZONE to "Europe/Berlin",
+            EventExportProjection.IDX_AVAILABILITY to CalendarContract.Events.AVAILABILITY_BUSY,
+        )
+
+        val event = reader.toIcsEvent(reminderMinutes = listOf(10), calendarName = "Personal")
+
+        assertThat(event.uid).isEqualTo("abc@host")
+        assertThat(event.summary).isEqualTo("Standup")
+        assertThat(event.start.toEpochMilliseconds()).isEqualTo(1_000_000L)
+        assertThat(event.end.toEpochMilliseconds()).isEqualTo(1_900_000L)
+        assertThat(event.isAllDay).isFalse()
+        assertThat(event.recurrenceRule).isNull()
+        assertThat(event.reminderMinutes).containsExactly(10)
+        assertThat(event.calendarName).isEqualTo("Personal")
+        assertThat(event.status).isEqualTo(EventStatus.Confirmed)
+    }
+
+    @Test
+    fun `recurring row without DTEND reconstructs end from DURATION`() {
+        val reader = MapColumnReader(
+            EventExportProjection.IDX_ID to 7L,
+            // No UID column → synthesised stably from id + dtstart.
+            EventExportProjection.IDX_TITLE to "Weekly",
+            EventExportProjection.IDX_DTSTART to 1_000_000L,
+            // DTEND absent (null); DURATION carries the length.
+            EventExportProjection.IDX_DURATION to "P3600S",
+            EventExportProjection.IDX_ALL_DAY to 0,
+            EventExportProjection.IDX_RRULE to "FREQ=WEEKLY",
+            EventExportProjection.IDX_EVENT_TIMEZONE to "UTC",
+        )
+
+        val event = reader.toIcsEvent(reminderMinutes = emptyList(), calendarName = null)
+
+        assertThat(event.uid).isEqualTo("7-1000000@calendula")
+        assertThat(event.recurrenceRule).isEqualTo("FREQ=WEEKLY")
+        assertThat(event.end.toEpochMilliseconds()).isEqualTo(1_000_000L + 3_600_000L)
+    }
+
+    @Test
+    fun `all-day flag is carried through`() {
+        val reader = MapColumnReader(
+            EventExportProjection.IDX_ID to 1L,
+            EventExportProjection.IDX_TITLE to "Holiday",
+            EventExportProjection.IDX_DTSTART to 0L,
+            EventExportProjection.IDX_DTEND to 86_400_000L,
+            EventExportProjection.IDX_ALL_DAY to 1,
+            EventExportProjection.IDX_EVENT_TIMEZONE to "UTC",
+        )
+
+        assertThat(reader.toIcsEvent(emptyList(), null).isAllDay).isTrue()
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/data/prefs/SettingsPrefsTest.kt

@@ -121,6 +121,118 @@ class SettingsPrefsTest {
         assertThat(prefs.reminderOnboardingDone.first()).isTrue()
     }
 
+    @Test
+    fun `default reminder is none until set`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        assertThat(prefs.defaultReminderMinutes.first()).isNull()
+    }
+
+    @Test
+    fun `default reminder round-trips, including none`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        prefs.setDefaultReminderMinutes(30)
+        assertThat(prefs.defaultReminderMinutes.first()).isEqualTo(30)
+        prefs.setDefaultReminderMinutes(null)
+        assertThat(prefs.defaultReminderMinutes.first()).isNull()
+    }
+
+    @Test
+    fun `garbage stored default reminder reads as none`(@TempDir tempDir: Path) = runTest {
+        val store = newDataStore(tempDir)
+        val prefs = SettingsPrefs(store)
+        store.updateData { p ->
+            val m = p.toMutablePreferences()
+            m[SettingsPrefs.DEFAULT_REMINDER_KEY] = "soon"
+            m
+        }
+        assertThat(prefs.defaultReminderMinutes.first()).isNull()
+    }
+
+    @Test
+    fun `per-calendar override round-trips minutes, none, and inherit`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        assertThat(prefs.perCalendarReminderOverride.first()).isEmpty()
+
+        prefs.setCalendarReminderOverride(7L, CalendarReminderOverride.Minutes(15))
+        prefs.setCalendarReminderOverride(9L, CalendarReminderOverride.None)
+        prefs.perCalendarReminderOverride.first().let { map ->
+            assertThat(map).containsExactly(7L, 15, 9L, null)
+        }
+
+        // Inherit drops the override entirely (absent != null value).
+        prefs.setCalendarReminderOverride(9L, CalendarReminderOverride.Inherit)
+        prefs.perCalendarReminderOverride.first().let { map ->
+            assertThat(map).containsExactly(7L, 15)
+            assertThat(map.containsKey(9L)).isFalse()
+        }
+    }
+
+    @Test
+    fun `all-day default round-trips, including none`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        assertThat(prefs.defaultAllDayReminderMinutes.first()).isNull()
+        prefs.setDefaultAllDayReminderMinutes(1_440)
+        assertThat(prefs.defaultAllDayReminderMinutes.first()).isEqualTo(1_440)
+        prefs.setDefaultAllDayReminderMinutes(null)
+        assertThat(prefs.defaultAllDayReminderMinutes.first()).isNull()
+    }
+
+    @Test
+    fun `per-calendar all-day override round-trips independently of the timed one`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        prefs.setCalendarReminderOverride(7L, CalendarReminderOverride.Minutes(15))
+        prefs.setCalendarAllDayReminderOverride(7L, CalendarReminderOverride.Minutes(1_440))
+        assertThat(prefs.perCalendarReminderOverride.first()).containsExactly(7L, 15)
+        assertThat(prefs.perCalendarAllDayReminderOverride.first()).containsExactly(7L, 1_440)
+        // Clearing the all-day override leaves the timed one untouched.
+        prefs.setCalendarAllDayReminderOverride(7L, CalendarReminderOverride.Inherit)
+        assertThat(prefs.perCalendarAllDayReminderOverride.first()).isEmpty()
+        assertThat(prefs.perCalendarReminderOverride.first()).containsExactly(7L, 15)
+    }
+
+    @Test
+    fun `resolveDefaultReminder picks the kind-matching override or global`() {
+        val timed = mapOf(7L to 15, 9L to null)
+        val allDay = mapOf(7L to 2_880)
+        fun resolve(calendarId: Long?, isAllDay: Boolean) = resolveDefaultReminder(
+            timedGlobal = 30,
+            allDayGlobal = 1_440,
+            timedOverrides = timed,
+            allDayOverrides = allDay,
+            calendarId = calendarId,
+            isAllDay = isAllDay,
+        )
+        // Timed: minutes override, explicit none, inherit global, no calendar.
+        assertThat(resolve(7L, isAllDay = false)).isEqualTo(15)
+        assertThat(resolve(9L, isAllDay = false)).isNull()
+        assertThat(resolve(5L, isAllDay = false)).isEqualTo(30)
+        assertThat(resolve(null, isAllDay = false)).isEqualTo(30)
+        // All-day: its own override wins; absent → all-day global; a timed-only
+        // override (cal 9) does not bleed into all-day.
+        assertThat(resolve(7L, isAllDay = true)).isEqualTo(2_880)
+        assertThat(resolve(9L, isAllDay = true)).isEqualTo(1_440)
+        assertThat(resolve(5L, isAllDay = true)).isEqualTo(1_440)
+    }
+
+    @Test
+    fun `all-day reminder time defaults to 9am`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        assertThat(prefs.allDayReminderTimeMinutes.first()).isEqualTo(540)
+    }
+
+    @Test
+    fun `all-day reminder time round-trips and clamps to a valid minute-of-day`(
+        @TempDir tempDir: Path,
+    ) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        prefs.setAllDayReminderTimeMinutes(8 * 60 + 30)
+        assertThat(prefs.allDayReminderTimeMinutes.first()).isEqualTo(510)
+        prefs.setAllDayReminderTimeMinutes(5_000)
+        assertThat(prefs.allDayReminderTimeMinutes.first()).isEqualTo(1_439)
+        prefs.setAllDayReminderTimeMinutes(-10)
+        assertThat(prefs.allDayReminderTimeMinutes.first()).isEqualTo(0)
+    }
+
     @Test
     fun `explicit week-start prefs resolve regardless of locale`() {
         assertThat(WeekStartPref.MONDAY.resolveFirstDay(Locale.US)).isEqualTo(DayOfWeek.MONDAY)

app/src/test/java/de/jeanlucmakiola/calendula/domain/ics/IcsDurationTest.kt

@@ -0,0 +1,28 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+
+class IcsDurationTest {
+
+    @Test
+    fun `parses the single-unit forms Calendula writes plus general ones`() {
+        assertThat(parseRfc2445DurationMillis("P1D")).isEqualTo(86_400_000L)
+        assertThat(parseRfc2445DurationMillis("P3600S")).isEqualTo(3_600_000L)
+        assertThat(parseRfc2445DurationMillis("PT1H30M")).isEqualTo(5_400_000L)
+        assertThat(parseRfc2445DurationMillis("P1W")).isEqualTo(604_800_000L)
+    }
+
+    @Test
+    fun `is sign-aware for before-start VALARM triggers`() {
+        assertThat(parseRfc2445DurationMillis("-PT15M")).isEqualTo(-900_000L)
+        assertThat(parseRfc2445DurationMillis("PT0M")).isEqualTo(0L)
+    }
+
+    @Test
+    fun `unparseable input is zero`() {
+        assertThat(parseRfc2445DurationMillis(null)).isEqualTo(0L)
+        assertThat(parseRfc2445DurationMillis("")).isEqualTo(0L)
+        assertThat(parseRfc2445DurationMillis("nonsense")).isEqualTo(0L)
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/domain/ics/IcsParserTest.kt

@@ -0,0 +1,168 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import com.google.common.truth.Truth.assertThat
+import de.jeanlucmakiola.calendula.domain.Availability
+import de.jeanlucmakiola.calendula.domain.EventStatus
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.atStartOfDayIn
+import kotlinx.datetime.toInstant
+import org.junit.jupiter.api.Test
+import kotlin.time.Instant
+
+class IcsParserTest {
+
+    private val parser = IcsParser(deviceZone = TimeZone.of("Europe/Berlin"))
+    private val writer = IcsWriter()
+    private val stamp = LocalDateTime(2026, 6, 18, 9, 30, 0).toInstant(TimeZone.UTC)
+
+    private fun roundTrip(event: IcsEvent): ParsedIcsEvent {
+        val text = writer.writeCalendar(listOf(event), stamp)
+        val result = parser.parse(text)
+        assertThat(result.events).hasSize(1)
+        return result.events.single()
+    }
+
+    private fun instantUtc(y: Int, mo: Int, d: Int, h: Int, mi: Int): Instant =
+        LocalDateTime(y, mo, d, h, mi, 0).toInstant(TimeZone.UTC)
+
+    @Test
+    fun `round-trips a timed one-off event`() {
+        val event = IcsEvent(
+            uid = "u1@calendula",
+            summary = "Lunch; with, friends",
+            start = instantUtc(2026, 6, 18, 11, 0),
+            end = instantUtc(2026, 6, 18, 12, 0),
+            isAllDay = false,
+            zoneId = "Europe/Berlin",
+            location = "Café",
+            availability = Availability.Free,
+            status = EventStatus.Tentative,
+        )
+        val parsed = roundTrip(event)
+        assertThat(parsed.uid).isEqualTo("u1@calendula")
+        assertThat(parsed.summary).isEqualTo("Lunch; with, friends")
+        assertThat(parsed.start).isEqualTo(event.start)
+        assertThat(parsed.end).isEqualTo(event.end)
+        assertThat(parsed.isAllDay).isFalse()
+        assertThat(parsed.location).isEqualTo("Café")
+        assertThat(parsed.availability).isEqualTo(Availability.Free)
+        assertThat(parsed.status).isEqualTo(EventStatus.Tentative)
+    }
+
+    @Test
+    fun `round-trips a recurring TZID event to the same instant`() {
+        val event = IcsEvent(
+            uid = "u2@calendula",
+            summary = "Weekly",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 14, 0),
+            isAllDay = false,
+            zoneId = "Europe/Berlin",
+            recurrenceRule = "FREQ=WEEKLY",
+        )
+        val parsed = roundTrip(event)
+        assertThat(parsed.start).isEqualTo(event.start)
+        assertThat(parsed.end).isEqualTo(event.end)
+        assertThat(parsed.zoneId).isEqualTo("Europe/Berlin")
+        assertThat(parsed.recurrenceRule).isEqualTo("FREQ=WEEKLY")
+    }
+
+    @Test
+    fun `round-trips an all-day event`() {
+        val event = IcsEvent(
+            uid = "u3@calendula",
+            summary = "Holiday",
+            start = LocalDate(2026, 6, 18).atStartOfDayIn(TimeZone.UTC),
+            end = LocalDate(2026, 6, 19).atStartOfDayIn(TimeZone.UTC),
+            isAllDay = true,
+            zoneId = "UTC",
+        )
+        val parsed = roundTrip(event)
+        assertThat(parsed.isAllDay).isTrue()
+        assertThat(parsed.start).isEqualTo(event.start)
+        assertThat(parsed.end).isEqualTo(event.end)
+    }
+
+    @Test
+    fun `round-trips reminders as before-start lead minutes`() {
+        val event = IcsEvent(
+            uid = "u4@calendula",
+            summary = "Meeting",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 14, 0),
+            isAllDay = false,
+            zoneId = "UTC",
+            reminderMinutes = listOf(15, 0),
+        )
+        val parsed = roundTrip(event)
+        assertThat(parsed.reminderMinutes).containsExactly(15, 0)
+    }
+
+    @Test
+    fun `tolerates folded lines and a missing UID`() {
+        val ics = buildString {
+            append("BEGIN:VCALENDAR\r\n")
+            append("VERSION:2.0\r\n")
+            append("BEGIN:VEVENT\r\n")
+            // Folded DESCRIPTION (continuation line begins with a space).
+            append("DESCRIPTION:This is a long descriptio\r\n n that was folded\r\n")
+            append("SUMMARY:No UID here\r\n")
+            append("DTSTART:20260618T090000Z\r\n")
+            append("DTEND:20260618T100000Z\r\n")
+            append("END:VEVENT\r\n")
+            append("END:VCALENDAR\r\n")
+        }
+        val parsed = parser.parse(ics).events.single()
+        assertThat(parsed.uid).isNull()
+        assertThat(parsed.description).isEqualTo("This is a long description that was folded")
+        assertThat(parsed.summary).isEqualTo("No UID here")
+    }
+
+    @Test
+    fun `skips a RECURRENCE-ID override and reports it`() {
+        val ics = "BEGIN:VCALENDAR\r\nBEGIN:VEVENT\r\nUID:x\r\n" +
+            "RECURRENCE-ID:20260618T090000Z\r\nDTSTART:20260618T090000Z\r\n" +
+            "SUMMARY:Override\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"
+        val result = parser.parse(ics)
+        assertThat(result.events).isEmpty()
+        assertThat(result.warnings).contains(IcsParseWarning.ModifiedOccurrenceSkipped)
+    }
+
+    @Test
+    fun `reports ignored attendees but still imports the event`() {
+        val ics = "BEGIN:VCALENDAR\r\nBEGIN:VEVENT\r\nUID:y\r\n" +
+            "DTSTART:20260618T090000Z\r\nSUMMARY:Has guests\r\n" +
+            "ATTENDEE;CN=Bob:mailto:bob@example.com\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"
+        val result = parser.parse(ics)
+        assertThat(result.events).hasSize(1)
+        assertThat(result.warnings).contains(IcsParseWarning.AttendeesIgnored)
+    }
+
+    @Test
+    fun `parses multiple events and carries the calendar name`() {
+        val events = listOf(
+            IcsEvent("a@c", "One", instantUtc(2026, 6, 18, 9, 0), instantUtc(2026, 6, 18, 10, 0),
+                false, "UTC", calendarName = "Personal"),
+            IcsEvent("b@c", "Two", instantUtc(2026, 6, 19, 9, 0), instantUtc(2026, 6, 19, 10, 0),
+                false, "UTC", calendarName = "Personal"),
+        )
+        val text = writer.writeCalendar(events, stamp)
+        val result = parser.parse(text)
+        assertThat(result.events).hasSize(2)
+        assertThat(result.events.map { it.calendarName }).containsExactly("Personal", "Personal")
+    }
+
+    @Test
+    fun `a malformed event does not sink the rest of the file`() {
+        // First VEVENT has no DTSTART (skipped); second is valid.
+        val ics = "BEGIN:VCALENDAR\r\n" +
+            "BEGIN:VEVENT\r\nUID:bad\r\nSUMMARY:No start\r\nEND:VEVENT\r\n" +
+            "BEGIN:VEVENT\r\nUID:good\r\nDTSTART:20260618T090000Z\r\nSUMMARY:Fine\r\nEND:VEVENT\r\n" +
+            "END:VCALENDAR\r\n"
+        val result = parser.parse(ics)
+        assertThat(result.events.map { it.uid }).containsExactly("good")
+        assertThat(result.warnings).contains(IcsParseWarning.EventWithoutStartSkipped)
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/domain/ics/IcsTextTest.kt

@@ -0,0 +1,57 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+
+class IcsTextTest {
+
+    @Test
+    fun `escapes backslash semicolon comma and newline`() {
+        assertThat(escapeText("a\\b;c,d\ne"))
+            .isEqualTo("a\\\\b\\;c\\,d\\ne")
+    }
+
+    @Test
+    fun `backslash is escaped before its escape markers, not after`() {
+        // A single backslash must become exactly one escaped backslash, not
+        // accidentally combine with a following separator.
+        assertThat(escapeText("\\;")).isEqualTo("\\\\\\;")
+    }
+
+    @Test
+    fun `short line is returned unfolded`() {
+        val line = "SUMMARY:short"
+        assertThat(foldLine(line)).isEqualTo(line)
+    }
+
+    @Test
+    fun `long line folds into physical lines of at most 75 octets`() {
+        val line = "DESCRIPTION:" + "x".repeat(300)
+        val folded = foldLine(line)
+
+        val physical = folded.split(ICS_CRLF)
+        assertThat(physical.size).isGreaterThan(1)
+        physical.forEach { assertThat(it.toByteArray(Charsets.UTF_8).size).isAtMost(75) }
+        // Every continuation line begins with the single folding space.
+        physical.drop(1).forEach { assertThat(it).startsWith(" ") }
+    }
+
+    @Test
+    fun `unfolding a folded line restores the original`() {
+        val line = "DESCRIPTION:" + "abcdefg ".repeat(40).trim()
+        val unfolded = foldLine(line).replace(ICS_CRLF + " ", "")
+        assertThat(unfolded).isEqualTo(line)
+    }
+
+    @Test
+    fun `folding never splits a multi-byte character`() {
+        // 100 emoji (4 UTF-8 octets each) — a naive byte split would corrupt one.
+        val line = "X-NOTE:" + "😀".repeat(100)
+        val folded = foldLine(line)
+        // The reassembled content must still decode to the same string.
+        assertThat(folded.replace(ICS_CRLF + " ", "")).isEqualTo(line)
+        folded.split(ICS_CRLF).forEach {
+            assertThat(it.toByteArray(Charsets.UTF_8).size).isAtMost(75)
+        }
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/domain/ics/IcsWriterTest.kt

@@ -0,0 +1,152 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import com.google.common.truth.Truth.assertThat
+import de.jeanlucmakiola.calendula.domain.Availability
+import de.jeanlucmakiola.calendula.domain.EventStatus
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.atStartOfDayIn
+import kotlinx.datetime.toInstant
+import org.junit.jupiter.api.Test
+import kotlin.time.Instant
+
+class IcsWriterTest {
+
+    private val writer = IcsWriter(prodId = "-//Test//Test//EN")
+    private val stamp = LocalDateTime(2026, 6, 18, 9, 30, 0).toInstant(TimeZone.UTC)
+
+    private fun lines(events: List<IcsEvent>): List<String> =
+        writer.writeCalendar(events, stamp).split(ICS_CRLF)
+
+    private fun instantUtc(y: Int, mo: Int, d: Int, h: Int, mi: Int): Instant =
+        LocalDateTime(y, mo, d, h, mi, 0).toInstant(TimeZone.UTC)
+
+    @Test
+    fun `calendar is wrapped with the required header and CRLF endings`() {
+        val out = writer.writeCalendar(emptyList(), stamp)
+        assertThat(out).startsWith("BEGIN:VCALENDAR\r\n")
+        assertThat(out).endsWith("END:VCALENDAR\r\n")
+        assertThat(out).contains("VERSION:2.0\r\n")
+        assertThat(out).contains("PRODID:-//Test//Test//EN\r\n")
+    }
+
+    @Test
+    fun `timed one-off event writes UTC instants with a Z suffix`() {
+        val event = IcsEvent(
+            uid = "u1@calendula",
+            summary = "Standup",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 13, 30),
+            isAllDay = false,
+            zoneId = "Europe/Berlin",
+        )
+        val l = lines(listOf(event))
+        assertThat(l).contains("DTSTART:20260618T130000Z")
+        assertThat(l).contains("DTEND:20260618T133000Z")
+        assertThat(l).contains("UID:u1@calendula")
+        assertThat(l).contains("STATUS:CONFIRMED")
+        assertThat(l).contains("TRANSP:OPAQUE")
+    }
+
+    @Test
+    fun `recurring timed event anchors to wall-clock with TZID`() {
+        // 13:00 UTC == 15:00 Berlin in summer; the series must read 15:00 local.
+        val event = IcsEvent(
+            uid = "u2@calendula",
+            summary = "Weekly",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 14, 0),
+            isAllDay = false,
+            zoneId = "Europe/Berlin",
+            recurrenceRule = "FREQ=WEEKLY",
+        )
+        val l = lines(listOf(event))
+        assertThat(l).contains("DTSTART;TZID=Europe/Berlin:20260618T150000")
+        assertThat(l).contains("DTEND;TZID=Europe/Berlin:20260618T160000")
+        assertThat(l).contains("RRULE:FREQ=WEEKLY")
+    }
+
+    @Test
+    fun `recurring event with an unknown zone falls back to UTC instants`() {
+        val event = IcsEvent(
+            uid = "u3@calendula",
+            summary = "Weekly",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 14, 0),
+            isAllDay = false,
+            zoneId = "Mars/Olympus",
+            recurrenceRule = "FREQ=WEEKLY",
+        )
+        val l = lines(listOf(event))
+        assertThat(l).contains("DTSTART:20260618T130000Z")
+        assertThat(l).contains("DTEND:20260618T140000Z")
+    }
+
+    @Test
+    fun `all-day event writes exclusive DATE values without a zone`() {
+        val start = LocalDate(2026, 6, 18).atStartOfDayIn(TimeZone.UTC)
+        val end = LocalDate(2026, 6, 19).atStartOfDayIn(TimeZone.UTC)
+        val event = IcsEvent(
+            uid = "u4@calendula",
+            summary = "Holiday",
+            start = start,
+            end = end,
+            isAllDay = true,
+            zoneId = "UTC",
+        )
+        val l = lines(listOf(event))
+        assertThat(l).contains("DTSTART;VALUE=DATE:20260618")
+        assertThat(l).contains("DTEND;VALUE=DATE:20260619")
+    }
+
+    @Test
+    fun `reminders become VALARM blocks with before-start triggers`() {
+        val event = IcsEvent(
+            uid = "u5@calendula",
+            summary = "Meeting",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 14, 0),
+            isAllDay = false,
+            zoneId = "UTC",
+            reminderMinutes = listOf(15, 0, 15), // duplicate is dropped
+        )
+        val out = writer.writeCalendar(listOf(event), stamp)
+        val l = out.split(ICS_CRLF)
+        assertThat(l.count { it == "BEGIN:VALARM" }).isEqualTo(2)
+        assertThat(l).contains("TRIGGER:-PT15M")
+        assertThat(l).contains("TRIGGER:PT0M")
+        assertThat(l).contains("ACTION:DISPLAY")
+    }
+
+    @Test
+    fun `text fields and the calendar name are escaped`() {
+        val event = IcsEvent(
+            uid = "u6@calendula",
+            summary = "Lunch; with, notes",
+            start = instantUtc(2026, 6, 18, 13, 0),
+            end = instantUtc(2026, 6, 18, 14, 0),
+            isAllDay = false,
+            zoneId = "UTC",
+            location = "Cafe\\Bar",
+            availability = Availability.Free,
+            status = EventStatus.Tentative,
+            calendarName = "Work, Personal",
+        )
+        val l = lines(listOf(event))
+        assertThat(l).contains("SUMMARY:Lunch\\; with\\, notes")
+        assertThat(l).contains("LOCATION:Cafe\\\\Bar")
+        assertThat(l).contains("STATUS:TENTATIVE")
+        assertThat(l).contains("TRANSP:TRANSPARENT")
+        assertThat(l).contains("X-CALENDULA-CALENDAR:Work\\, Personal")
+    }
+
+    @Test
+    fun `existing uid is kept and a missing one is synthesised stably`() {
+        assertThat(deriveIcsUid("real-uid@host", 7, 1000)).isEqualTo("real-uid@host")
+        assertThat(deriveIcsUid(null, 7, 1000)).isEqualTo("7-1000@calendula")
+        assertThat(deriveIcsUid("  ", 7, 1000)).isEqualTo("7-1000@calendula")
+        // Stable across calls — a re-export of the same row yields the same UID.
+        assertThat(deriveIcsUid(null, 7, 1000)).isEqualTo(deriveIcsUid(null, 7, 1000))
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/domain/ics/ParsedIcsFormTest.kt

@@ -0,0 +1,54 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import com.google.common.truth.Truth.assertThat
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.atStartOfDayIn
+import kotlinx.datetime.toInstant
+import org.junit.jupiter.api.Test
+
+class ParsedIcsFormTest {
+
+    private val berlin = TimeZone.of("Europe/Berlin")
+
+    @Test
+    fun `timed event maps to wall-clock form times in the device zone`() {
+        val event = ParsedIcsEvent(
+            uid = "u@x",
+            summary = "Call",
+            start = LocalDateTime(2026, 6, 18, 13, 0, 0).toInstant(TimeZone.UTC),
+            end = LocalDateTime(2026, 6, 18, 14, 0, 0).toInstant(TimeZone.UTC),
+            isAllDay = false,
+            zoneId = "UTC",
+            reminderMinutes = listOf(10, 10, 5),
+            recurrenceRule = "FREQ=WEEKLY",
+        )
+        val form = event.toEventForm(berlin)
+
+        assertThat(form.calendarId).isNull()
+        assertThat(form.title).isEqualTo("Call")
+        // 13:00 UTC == 15:00 Berlin (summer).
+        assertThat(form.start).isEqualTo(LocalDateTime(2026, 6, 18, 15, 0, 0))
+        assertThat(form.end).isEqualTo(LocalDateTime(2026, 6, 18, 16, 0, 0))
+        assertThat(form.reminders).containsExactly(5, 10).inOrder()
+        assertThat(form.rrule).isEqualTo("FREQ=WEEKLY")
+    }
+
+    @Test
+    fun `all-day event shows the last covered day, not the exclusive end`() {
+        val event = ParsedIcsEvent(
+            uid = null,
+            summary = "Trip",
+            start = LocalDate(2026, 6, 18).atStartOfDayIn(TimeZone.UTC),
+            end = LocalDate(2026, 6, 20).atStartOfDayIn(TimeZone.UTC), // exclusive
+            isAllDay = true,
+            zoneId = "UTC",
+        )
+        val form = event.toEventForm(berlin)
+
+        assertThat(form.isAllDay).isTrue()
+        assertThat(form.start.date).isEqualTo(LocalDate(2026, 6, 18))
+        assertThat(form.end.date).isEqualTo(LocalDate(2026, 6, 19)) // last covered day
+    }
+}

app/src/test/java/de/jeanlucmakiola/calendula/ui/week/WeekLayoutTest.kt

@@ -62,13 +62,28 @@ class WeekLayoutTest {
         assertThat(ev.coversDay(wed, zone)).isTrue()
         assertThat(ev.coversDay(mon, zone)).isFalse()
 
-        val multiDay = event(at(mon, 22), at(wed, 2), allDay = true)
+        // All-day: UTC midnights, end exclusive. Mon..Tue covers Mon and Tue
+        // but not Wed (the Wed-midnight end is exclusive).
+        val multiDay = event(at(mon, 0), at(wed, 0), allDay = true)
         assertThat(multiDay.coversDay(mon, zone)).isTrue()
         assertThat(multiDay.coversDay(LocalDate(2026, 6, 9), zone)).isTrue()
-        assertThat(multiDay.coversDay(wed, zone)).isTrue()
+        assertThat(multiDay.coversDay(wed, zone)).isFalse()
         assertThat(multiDay.coversDay(LocalDate(2026, 6, 12), zone)).isFalse()
     }
 
+    @Test
+    fun `single-day all-day event does not leak into the next day east of UTC`() {
+        // A birthday on Wed: the provider stores UTC midnights with an exclusive
+        // end (Thu 00:00 UTC). In a zone east of UTC the device-local day must
+        // still resolve to Wed only — never Thu. Regression for the all-day
+        // event appearing on two days in the views.
+        val berlin = TimeZone.of("Europe/Berlin") // UTC+2 in June
+        val ev = event(at(wed, 0), at(wed.plusDays(1), 0), allDay = true)
+        assertThat(ev.coversDay(wed, berlin)).isTrue()
+        assertThat(ev.coversDay(wed.plusDays(1), berlin)).isFalse()
+        assertThat(ev.coversDay(wed.plusDays(-1), berlin)).isFalse()
+    }
+
     @Test
     fun `single timed event gets one lane`() {
         val blocks = layoutDay(listOf(event(at(wed, 9), at(wed, 10, 30))), wed, zone)

docs/superpowers/plans/2026-06-18-05-ics-export.md

@@ -0,0 +1,150 @@
+# Calendula - Plan 05: ICS Export (v2.7, Branch 1 von 2)
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Die Schreib-Hälfte des `.ics`-Themas. Calendula serialisiert eigene
+Events nach RFC 5545 — als Einzel-Event (Share-Sheet) und als
+Ganz-Kalender-Backup (SAF-Datei). Damit existiert für gerätelokale Kalender
+(`ACCOUNT_TYPE_LOCAL`) zum ersten Mal ein Backup; ohne Sync ist ein verlorenes
+Gerät sonst Totalverlust. Diese Branch baut **nur Export**; Import
+(Parser, Restore, Open-into-form) folgt in Branch 2 (`feat/ics-import`),
+beide landen zusammen in **einem** Release v2.7.0 — es gibt also keine
+Zwischenversion, die UIDs schreibt, ohne sie je zu lesen.
+`./gradlew lint test assembleDebug` bleibt grün; Release erst nach
+On-Device-Review (gemeinsam mit Branch 2).
+
+**Architecture:** Neue reine-Kotlin-Engine `domain/ics/` — kein
+`CalendarContract`, keine Android-Deps, voll JVM-testbar. Kern ist
+`IcsWriter` (nimmt eine Liste eigener Event-Modelle + Kalender-Metadaten,
+gibt einen `VCALENDAR`-String zurück). Keine ICS-Library: wir bleiben auf
+`kotlinx-datetime` (kein `java.time`-Desugaring) und hand-rollen wie schon
+bei RRULE in `Recurrence.kt`. Das Schreiben in eine SAF-Datei / das
+Share-Intent liegt in einer dünnen Android-Schicht
+(`data/ics/IcsExporter` o. ä.), die Provider-Reads → Domain-Modelle →
+`IcsWriter` → `OutputStream` verdrahtet.
+
+**Recherche-Befunde (Codebase, 2026-06-18):**
+
+1. **Keine ICS-Library, kein `java.time`-Desugaring** — Stack ist
+   `kotlinx-datetime` + `kotlin.time.Instant`. RRULE wird bereits in
+   `domain/Recurrence.kt` von Hand geparst/gerendert (inkl. der sorgfältigen
+   `UNTIL`/DST-Korrektur). `IcsWriter` reiht sich in genau diese Kultur ein und
+   nutzt `SimpleRecurrence.toRRule()` direkt.
+2. **Kein UID-Handling.** `Events.UID_2445` wird heute nirgends gelesen oder
+   geschrieben. Für idempotenten Restore in Branch 2 muss Import auf UID
+   matchen — ohne UID verdoppelt ein erneuter Import alles. Darum schreibt
+   **diese** Branch bereits UID bei jedem Insert (Vorarbeit; ohne Import noch
+   unsichtbar, zahlt sich erst in Branch 2 aus — beide im selben Release).
+3. **Zeitzonen werden gespeichert, aber nie vom Nutzer gewählt.** Lesen/Anzeige:
+   `EVENT_TIMEZONE` landet in `EventDetail.eventTimezone`, das Detail zeigt ein
+   Fremdzonen-Label nur bei Abweichung vom Gerät (`foreignTimeZoneLabel`).
+   Schreiben (`EventWriteMapper.toWriteTimes`): all-day → UTC-Mitternachten,
+   `EVENT_TIMEZONE="UTC"`; getimt → `EVENT_TIMEZONE = zone.id`, und alle Caller
+   übergeben `currentSystemDefault()` (kein Zonen-Feld im Formular). Jedes selbst
+   erstellte Event trägt also die Gerätezone zum Erstellzeitpunkt; eingesynkte
+   Events behalten ihre Originalzone.
+
+**Leitentscheidungen:**
+
+1. **Zeitzonen-Regel beim Schreiben (fallbasiert):**
+   - **All-day** → `DTSTART;VALUE=DATE:YYYYMMDD`, `DTEND` exklusiv
+     (Tag-danach). Keine Zone — trivial korrekt.
+   - **Getimt, nicht wiederkehrend** → UTC-Instant `…T…Z`. Ein Instant ist ein
+     Instant; die Anzeige rechnet beim Import wieder in die Gerätezone. Verlustfrei.
+   - **Getimt, wiederkehrend** → `DTSTART;TZID=<EVENT_TIMEZONE>:<lokale Wandzeit>`.
+     Eine Serie muss an der **Wandzeit** verankert sein, sonst driftet ein
+     „wöchentlich 9 Uhr" über die nächste DST-Grenze um eine Stunde. Die Zone
+     liegt bereits in `EVENT_TIMEZONE` vor; die lokale Wandzeit ist eine
+     `kotlinx-datetime`-Konversion (Instant → LocalDateTime in der Zone).
+   - **`VTIMEZONE`-Blöcke werden bewusst NICHT emittiert.** Beim eigenen
+     Round-Trip löst Branch-2-Import `TZID` gegen die OS-tz-Datenbank auf
+     (`kotlinx-datetime`/`java.time` kennen jede IANA-Id). Technisch nicht
+     RFC-konform; einziger Preis sind strenge Fremd-Parser ohne tz-DB — als
+     bekannte Lücke dokumentiert (Skip-and-report-Territorium des Imports),
+     kein Blocker. Voll-`VTIMEZONE` ist „später, falls nötig".
+2. **UID bei jedem Insert.** `insertEvent` schreibt fortan `Events.UID_2445`
+   (z. B. `<random-uuid>@calendula`). Bestehende Events ohne UID exportieren
+   wir mit einer **deterministischen, stabilen** Fallback-UID, abgeleitet aus
+   `event-id + DTSTART` (`<id>-<dtstart>@calendula`), damit derselbe Bestand
+   über mehrere Backups dieselbe UID behält und Branch-2-Restore nicht
+   verdoppelt. Bestehende Rows werden **nicht** rückwirkend gestempelt
+   (kein Migrations-Sweep über fremde Kalender).
+3. **Manueller Export, kein Background.** Backup via
+   `ACTION_CREATE_DOCUMENT` (SAF, MIME `text/calendar`, Default-Name
+   `calendula-backup-<datum>.ics`); Einzel-Event-Share via `ACTION_SEND` mit
+   einem `FileProvider`-Cache-File (`text/calendar`). Kein WorkManager, kein
+   geplantes/automatisches Backup (passt zum „kein Hintergrunddienst"-Ethos;
+   Auto-Backup bleibt explizit Roadmap-`later`).
+4. **Backup-Layout: eine kombinierte `VCALENDAR`-Datei** über alle
+   gerätelokalen (beschreibbaren) Kalender. Pro Event ein `VEVENT`; die
+   Kalender-Zugehörigkeit reist als `X-WR-CALNAME` / `CATEGORIES` o. ä. mit,
+   damit Branch-2-Restore wieder auffächern oder per Ziel-Picker einsortieren
+   kann. Eine Datei ist einfacher zu teilen/abzulegen als n Dateien.
+   *Offen, vor dem Backup-Task zu fixieren:* exaktes Property fürs
+   Kalender-Mapping (`X-WR-CALNAME` pro `VCALENDAR` erlaubt nur einen Namen;
+   für mehrere Kalender in einer Datei brauchen wir ein Pro-`VEVENT`-Property
+   wie `X-CALENDULA-CALENDAR` oder `CATEGORIES`).
+5. **Feldumfang = was Calendula modelliert.** `IcsWriter` serialisiert genau
+   die gelesenen Felder: `SUMMARY`, `DTSTART`/`DTEND` (Regel #1),
+   `LOCATION`, `DESCRIPTION`, `RRULE` (über `toRRule`), `VALARM` aus den
+   Remindern (DISPLAY, `TRIGGER` = `-PT<min>M`), `STATUS`
+   (CONFIRMED/TENTATIVE/CANCELLED), `TRANSP` (Free→TRANSPARENT/Busy→OPAQUE),
+   `UID`, `DTSTAMP`. Felder ohne sauberes Modell (Attendees, RECURRENCE-ID-
+   Ausnahmen) bleiben **vorerst weg** — Export erzeugt nichts, was Import in
+   Branch 2 nicht auch wieder lesen kann.
+6. **Korrekte RFC-5545-Mechanik:** Zeilen-Folding bei >75 Oktett (CRLF +
+   Space-Fortsetzung), Text-Escaping (`\` `;` `,` `\n`), CRLF-Zeilenenden,
+   `PRODID`/`VERSION:2.0`-Header. Eine reine, einzeln getestete Hilfsschicht
+   (`IcsLine`/`fold`/`escapeText`), nicht ad hoc im Writer verstreut.
+
+---
+
+## Tasks
+
+**Domain-Engine (`domain/ics/`, reine Kotlin, JVM-Tests):**
+- [x] `IcsText`: `escapeText`, `foldLine` (75-Oktett, CRLF+Space) + Test
+      (`IcsTextTest`). Wert-Helfer (Instant→`…T…Z`, Wandzeit→`TZID`,
+      LocalDate→`VALUE=DATE`) leben als private Helfer in `IcsWriter`.
+- [x] `IcsEvent`-Eingabemodell (reine Kotlin: summary, start/end als Instant
+      + isAllDay + zoneId, recurrenceRule?, location, description,
+      reminderMinutes, status, availability, uid, calendarName) — entkoppelt
+      vom Provider-Modell
+- [x] `IcsWriter.writeCalendar(events, dtStamp)` → String: Header, pro Event
+      `VEVENT` nach Entscheidung #5, Zeitzonen-Regel #1, `VALARM`; JVM-Test
+      `IcsWriterTest` (all-day, getimt, wiederkehrend+TZID, unbekannte Zone,
+      Reminder, Escaping)
+- [x] UID-Ableitung `deriveIcsUid` (`uid ?: "<eventId>-<dtstartMillis>@calendula"`)
+      + Stabilitätstest
+
+**Provider → Domain (`data/calendar/IcsExportMapper.kt`):**
+- [x] Mapper Provider-Row → `IcsEvent` (`ColumnReader.toIcsEvent`) inkl.
+      DURATION→DTEND-Rekonstruktion (`parseRfc2445DurationMillis`),
+      `EventExportProjection`; Datasource-Methode `exportableEvents()` +
+      Repository `exportEvents()`; Test `IcsExportMapperTest`
+- [x] `insertEvent` schreibt `Events.UID_2445` (`UUID@calendula`) bei jedem
+      Create
+
+**Android-Export-Schicht:**
+- [x] `data/ics/IcsExporter`: `writeDocument(uri)` (SAF) + `stageShareFile`
+      (FileProvider-Cache) als UTF-8
+- [x] Einzel-Event-Share: Share-Action im Event-Detail → `IcsWriter` für ein
+      Event (one-off) → Cache-File über `FileProvider` → `ACTION_SEND`
+- [x] Ganz-Kalender-Backup: „Export as .ics file" in Settings → Calendars →
+      `ACTION_CREATE_DOCUMENT` → in den URI streamen; Ergebnis-Snackbar
+      (Plural „Exported N events")
+- [x] `FileProvider` + `file_paths.xml` im Manifest (Cache-Dir für Shares)
+- [x] Strings DE+EN: Share-Label/Chooser/Fehler, Backup-Sektion/Aktion/
+      Fehler + Plural, dateierter Default-Name
+
+**Abschluss:**
+- [ ] `./gradlew lint test assembleDebug` grün ← **nächster Schritt (Test)**
+- [x] CHANGELOG (`[Unreleased]`) ergänzt
+- [ ] On-Device-Review; **kein** Tag/Release vor Review und vor Merge von
+      Branch 2 (`feat/ics-import`)
+
+**Offene Detail-Calls (vor Review klären, nicht-blockierend):**
+- Kalender→Event-Mapping nutzt das per-`VEVENT`-Property `X-CALENDULA-CALENDAR`
+  (statt `X-WR-CALNAME`), damit eine kombinierte Datei mehrere Kalender trägt.
+- Backup = **eine** kombinierte `VCALENDAR`-Datei über alle lokalen Kalender.
+- EXDATE / `RECURRENCE-ID`-Ausnahmen werden beim Export ausgelassen
+  (`ORIGINAL_ID IS NULL`) — dokumentierter v1-Grenzfall, Import lässt sie auch aus.

docs/superpowers/plans/2026-06-18-06-ics-import.md

@@ -0,0 +1,122 @@
+# Calendula - Plan 06: ICS Import (v2.7, Branch 2 von 2)
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Die Lese-Hälfte des `.ics`-Themas, aufgesetzt auf den Writer aus
+Branch 1 (`feat/ics-export`, gemerged in `release/v2.7.0`). Calendula parst
+RFC-5545-Dateien und führt sie über zwei Wege ein: eine einzelne `VEVENT` öffnet
+das vorausgefüllte Erstellen-Formular (Review vor dem Speichern), eine Datei mit
+vielen Events geht in einen Bulk-Import mit Ziel-Kalender-Auswahl und
+Ergebnis-Report. Damit schließt sich der Backup→Restore-Kreis für lokale
+Kalender. Beide Branches landen in **einem** Release v2.7.0.
+`./gradlew lint test assembleDebug` bleibt grün; Release erst nach
+On-Device-Review.
+
+**Architecture:** `IcsParser` lebt rein in `domain/ics/` neben `IcsWriter` —
+kein Android, JVM-testbar, symmetrisch zum Writer. Ausgabe ist ein
+`IcsParseResult` (`events: List<ParsedIcsEvent>` + `warnings: List<String>`).
+`ParsedIcsEvent` ist die Parse-Variante von `IcsEvent` (gleiche Felder, aber
+`uid: String?` — eine eingelesene `VEVENT` kann ohne UID kommen). Zwei Adapter:
+`ParsedIcsEvent.toEventForm(zone)` (Einzel-Öffnen → `EventForm`) und eine
+Repository-Methode `importEvents(targetCalendarId, events)` → `ImportSummary`
+(Bulk). Datei-IO (`Uri` lesen, Intent) liegt in `data/ics/` bzw. der
+Activity/Compose-Schicht; Routing 1-vs-viele entscheidet anhand der geparsten
+Event-Anzahl.
+
+**Liberal-in/strict-out (Leitprinzip):** unbekannte Properties, fremde
+`VTIMEZONE`-Blöcke und `RECURRENCE-ID`-Ausnahmen werden **übersprungen und im
+Report vermerkt**, nie still verschluckt; ein einzelnes kaputtes `VEVENT` lässt
+den Rest der Datei durch.
+
+**Leitentscheidungen:**
+
+1. **Parse-Mechanik (Umkehr von `IcsText`):** zuerst **Unfolding** (CRLF +
+   Space/Tab → wegfalten), dann pro Zeile `NAME[;params]:value` zerlegen,
+   TEXT-Werte **unescapen** (`\\` `\;` `\,` `\n`). Eine reine, einzeln getestete
+   Schicht (`IcsLineParser`), nicht ad hoc im Walker.
+2. **Datum/Zeit-Parsing (Umkehr der Writer-Zeitzonenregel):**
+   - `VALUE=DATE` (`YYYYMMDD`) → all-day, Instant auf UTC-Mitternacht (wie der
+     Provider all-day speichert), exklusives `DTEND` bleibt exklusiv.
+   - `…T…Z` → UTC-Instant.
+   - `…T…` mit `TZID=<zone>` → lokale Wandzeit in der Zone, aufgelöst gegen die
+     **OS-tz-Datenbank** (`TimeZone.of`); unbekannte/fehlende `TZID` →
+     Gerätezone als Fallback (+ Warnung).
+   - Kein `VTIMEZONE`-Parsing — `TZID` wird gegen die OS-DB aufgelöst (s. Branch-1
+     Entscheidung); ein `VTIMEZONE`-Block wird übersprungen (Warnung nur, wenn
+     seine `TZID` nicht in der OS-DB ist).
+3. **Routing 1-vs-viele:** genau **eine** `VEVENT` → vorausgefülltes
+   Erstellen-Formular (`ParsedIcsEvent.toEventForm`, `calendarId=null` →
+   Formular wählt wie gehabt den zuletzt genutzten Kalender vor). **Mehr als
+   eine** → Bulk-Import-Screen (Ziel-Kalender-Picker, nur beschreibbare). Leere
+   Datei → freundlicher „nichts gefunden"-Hinweis.
+4. **UID-Dedup beim Bulk-Import:** vor dem Insert die vorhandenen
+   `Events.UID_2445` des Ziel-Kalenders lesen; eine eingelesene UID, die schon
+   existiert, wird **übersprungen** (gezählt als „bereits vorhanden"). v1:
+   skip-not-update — kein Überschreiben, das hält den Restore idempotent und
+   verlustfrei. Events ohne UID bekommen beim Insert eine frische
+   (`UUID@calendula`, wie `insertEvent`).
+5. **Empfang via Intent:** Manifest-`ACTION_VIEW`/`SEND` mit MIME `text/calendar`
+   (+ `.ics`-Pfadmuster für `file`/`content`-Schemes). `MainActivity`
+   (`singleTop`, wie beim Reminder-Tap) liest den `Uri`, parst, und reicht das
+   Ergebnis als Compose-State an `CalendarHost` (gleiches Key-Muster wie der
+   Notification-Deep-Link).
+6. **Reminder/Status/Transp zurück:** `VALARM` `TRIGGER` (negatives `-PT…`,
+   `PT0…`) → Lead-Minuten; `STATUS`/`TRANSP` → `EventStatus`/`Availability`.
+   `DURATION`-statt-`DTEND` über `parseRfc2445DurationMillis` (existiert aus
+   Branch 1). Attendees werden **nicht** importiert (kein Modell; Warnung wenn
+   vorhanden).
+
+**Recherche-Befunde (Codebase, 2026-06-18 — aus Branch 1):**
+- `IcsText.escapeText`/`foldLine` + `IcsWriter` existieren; Parser spiegelt sie.
+- `parseRfc2445DurationMillis` (in `IcsExportMapper.kt`) parst die
+  Provider-`DURATION`-Formen inkl. des nicht-standardkonformen `P<n>S`.
+- `EventForm` (Domain): Zeiten als `LocalDateTime` in Gerätezone, `calendarId`
+  nullable; das Formular wählt bei `null` den zuletzt genutzten Kalender vor.
+- `insertEvent` schreibt bereits `Events.UID_2445`; für den Import muss eine
+  **vorgegebene** UID durchgereicht werden (Insert-Variante / Parameter).
+
+---
+
+## Tasks
+
+**Parser-Engine (`domain/ics/`, reine Kotlin, JVM-Tests):**
+- [x] `IcsText`: `unescapeText` + `unfold(lines)` ergänzen (+ Test)
+- [x] `IcsLineParser`: `NAME;PARAM=v;PARAM=v:VALUE` → (name, params-map, value);
+      Param-Werte ggf. in Quotes; Test (Kantenfälle: Doppelpunkt im Wert,
+      gequotete Params)
+- [x] `ParsedIcsEvent` (wie `IcsEvent`, aber `uid: String?`) + Datum/Zeit-Parser
+      (`VALUE=DATE` / `…Z` / `TZID` → Instant + isAllDay + zoneId)
+- [x] `IcsParser.parse(text)` → `IcsParseResult(events, warnings)`: VCALENDAR/
+      VEVENT-Walk, skip-and-report für `RECURRENCE-ID`/unbekannte `VTIMEZONE`/
+      Attendees; ein defektes VEVENT killt nicht den Rest. **Round-trip-Test**
+      gegen `IcsWriter`-Ausgabe (all-day, getimt, wiederkehrend+TZID, Reminder)
+      + Fremd-Quirks (gefaltete Zeilen, fehlende UID, `PT…`-Trigger)
+
+**Datenschicht (`data/calendar/` + `data/ics/`):**
+- [x] `ParsedIcsEvent.toEventForm(zone)` (Einzel-Öffnen → `EventForm`); Test
+- [x] Datasource: `existingUids(calendarId)` (Query `Events.UID_2445`) +
+      `insertImported(event, calendarId)` (Insert mit vorgegebener/erzeugter UID)
+- [x] Repository `importEvents(targetCalendarId, events)` → `ImportSummary`
+      (imported / skippedDuplicate / skippedUnsupported); UID-Dedup; Test mit
+      Fake-Datasource
+- [x] `IcsImporter` (`data/ics/`): `Uri` → Text lesen (UTF-8, `contentResolver`)
+
+**Intent + Routing:**
+- [x] Manifest: `ACTION_VIEW`/`ACTION_SEND`, MIME `text/calendar`, `.ics`-
+      Pfadmuster (`file`/`content`); `MainActivity` parst eingehenden `Uri`
+- [x] Routing in `CalendarHost`: 1 Event → Erstellen-Formular vorausgefüllt;
+      >1 → Bulk-Import-Screen; 0 → Hinweis
+
+**UI:**
+- [x] Bulk-Import-Screen: Ziel-Kalender-Picker (OptionCard, nur beschreibbare),
+      Anzahl/Vorschau, Import-Button → `ImportSummary` als Ergebnis
+- [x] Einzel-Öffnen: `EventEditScreen` mit vorausgefülltem Formular (neuer
+      Prefill-Pfad im `EventEditViewModel`, ohne `eventId`)
+- [x] Strings DE+EN: Import-Titel, Ziel-Auswahl, Ergebnis-Plurals
+      (importiert / übersprungen-vorhanden / übersprungen-nicht-unterstützt),
+      leere-Datei-Hinweis
+
+**Abschluss:**
+- [x] `./gradlew lint test assembleDebug` grün
+- [ ] CHANGELOG done; ROADMAP/STATE pending; v2.7 cut **erst** wenn beide
+      Branches gemerged sind und On-Device-Review durch ist

renovate.json5

@@ -0,0 +1,56 @@
+{
+  $schema: "https://docs.renovatebot.com/renovate-schema.json",
+
+  extends: [
+    "config:recommended",
+    // chore(deps): … — match the repo's conventional-commit style.
+    ":semanticCommits",
+  ],
+
+  // No automerge: a dependency bump goes through the same review (and, for
+  // anything touching the build, the same on-device check) as a feature
+  // before it can ride a release — see docs/RELEASING.md and the
+  // "hold release for approval" rule.
+  automerge: false,
+
+  // One reviewable surface; the dashboard issue lists everything pending.
+  dependencyDashboard: true,
+  labels: ["dependencies"],
+  prConcurrentLimit: 5,
+  prHourlyLimit: 0,
+
+  // Cadence is owned by the Gitea Actions cron (.gitea/workflows/renovate.yml,
+  // Mondays) — no internal `schedule` here, so the two don't double-gate and
+  // silently skip a run.
+
+  // Gitea Actions workflows live under .gitea/workflows, not .github — extend
+  // the github-actions manager (same syntax) to watch them too.
+  "github-actions": {
+    fileMatch: ["^\\.gitea/workflows/[^/]+\\.ya?ml$"],
+  },
+
+  packageRules: [
+    // material3 is deliberately pinned to the 1.5 *alpha* line for the
+    // Expressive APIs (see gradle/libs.versions.toml). Follow the alpha train
+    // but keep it in its own PR, reviewed in isolation; revisit the pin when
+    // 1.5.0 stable lands.
+    {
+      matchPackageNames: ["androidx.compose.material3:material3"],
+      ignoreUnstable: false,
+      groupName: "material3 (alpha)",
+    },
+    // Test-only deps: group into one low-noise PR.
+    {
+      matchPackageNames: [
+        "org.junit.jupiter:**",
+        "org.junit.platform:**",
+        "com.google.truth:**",
+        "app.cash.turbine:**",
+        "androidx.test:**",
+        "androidx.test.espresso:**",
+        "androidx.test.ext:**",
+      ],
+      groupName: "test dependencies",
+    },
+  ],
+}

scripts/check_translations.py

@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+"""Validate Android translation resources against the base strings.xml.
+
+Community translations live in ``app/src/main/res/values-<locale>/strings.xml``
+and are produced via Weblate. This guard keeps incoming translation PRs honest:
+
+  * every translation file must be well-formed XML;
+  * a translation must not define keys absent from the base — those are stale
+    keys left behind after a rename/removal upstream;
+  * a translation must not translate strings marked ``translatable="false"`` in
+    the base (URLs, IDs and the like).
+
+Missing keys are *allowed* and only reported as coverage: a missing string
+falls back to the English base at runtime, so partial translations are fine
+(this mirrors the lint config, which downgrades ``MissingTranslation``).
+
+Exits non-zero if any error is found. Errors are emitted as Gitea/GitHub
+Actions ``::error`` annotations so they surface inline on the PR.
+"""
+from __future__ import annotations
+
+import sys
+import xml.etree.ElementTree as ET
+from pathlib import Path
+
+RES_DIR = Path("app/src/main/res")
+BASE = RES_DIR / "values" / "strings.xml"
+RESOURCE_TAGS = ("string", "plurals", "string-array")
+
+
+def entries(path: Path) -> dict[str, bool]:
+    """Map resource name -> is-translatable for every entry in ``path``."""
+    root = ET.parse(path).getroot()
+    return {
+        el.attrib["name"]: el.attrib.get("translatable", "true") != "false"
+        for el in root
+        if el.tag in RESOURCE_TAGS and "name" in el.attrib
+    }
+
+
+def main() -> int:
+    if not BASE.exists():
+        print(f"::error::base resource file {BASE} not found", file=sys.stderr)
+        return 1
+
+    base = entries(BASE)
+    base_keys = set(base)
+    nontranslatable = {name for name, ok in base.items() if not ok}
+    translatable_total = len(base_keys - nontranslatable)
+
+    files = sorted(RES_DIR.glob("values-*/strings.xml"))
+    if not files:
+        print("No translation files found (values-*/strings.xml).")
+        return 0
+
+    errors = 0
+    for path in files:
+        locale = path.parent.name[len("values-"):]
+        try:
+            translated = entries(path)
+        except ET.ParseError as exc:
+            print(f"::error file={path}::{locale}: malformed XML: {exc}")
+            errors += 1
+            continue
+
+        keys = set(translated)
+        stale = sorted(keys - base_keys)
+        translated_fixed = sorted(keys & nontranslatable)
+        missing = base_keys - nontranslatable - keys
+
+        for name in stale:
+            print(f"::error file={path}::{locale}: stale key '{name}' is not in the base strings.xml")
+            errors += 1
+        for name in translated_fixed:
+            print(
+                f"::error file={path}::{locale}: key '{name}' is translatable=\"false\" "
+                "in the base and must not be translated"
+            )
+            errors += 1
+
+        covered = translatable_total - len(missing)
+        pct = covered * 100 // translatable_total if translatable_total else 100
+        verdict = "OK" if not (stale or translated_fixed) else "FAIL"
+        print(f"{locale:<10} {covered}/{translatable_total} keys ({pct}%) — {verdict}")
+
+    if errors:
+        print(f"\n{errors} translation error(s) found.", file=sys.stderr)
+        return 1
+    print("\nAll translation files are consistent with the base.")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())