fix(deps): update composebom to v2026.06.00

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

.planning/ROADMAP.md

@@ -233,18 +233,25 @@ pass on the existing controls; new toggles ride in with their own features.
 8. App shortcuts: ~~launcher long-press → New event~~ *(done, v2.5.0)*; optional quick-settings tile still open
 
 **Tier 4 — reliability, data-safety & interop** *(re-ranked 2026-06-17)*
-9. **Reminders — defaults + delivery reliability** *(next)* — global default
-   reminder **+ per-calendar override**, bundled with exact-alarm / battery
-   hardening. Elevated above .ics: it's core to the "Calendula is your only
-   calendar app" promise. Full sketch in "Reminders — defaults & delivery
-   reliability" below.
-10. **Local-calendar backup / export** — device-only calendars have no sync and
-    therefore **no backup**; losing the phone = total data loss. Whole-calendar
-    `.ics` export + restore. A data-integrity gap, not a feature; front-runs and
-    overlaps the single-event .ics work below.
-11. Share event as .ics + receive/open .ics into a prefilled create form
+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)
-13. Snooze / dismiss notification actions — follows the reminders slice (#9)
 
 **Gated — explicit go/no-go before any work (mostly INTERNET-permission calls)**
 - Remote calendar create/edit (re-implements DAVx5; INTERNET + credential storage)

CHANGELOG.md

@@ -7,6 +7,31 @@ 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/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 = 20600
-        versionName = "2.6.0"
+        versionCode = 20700
+        versionName = "2.7.0"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }

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

@@ -47,6 +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"
@@ -112,6 +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

@@ -2,6 +2,7 @@ package de.jeanlucmakiola.calendula
 
 import android.content.Context
 import android.content.Intent
+import android.net.Uri
 import android.os.Bundle
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
@@ -12,6 +13,7 @@ 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
@@ -35,11 +37,16 @@ class MainActivity : AppCompatActivity() {
     // 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 : AppCompatActivity() {
                     onDetailKeyConsumed = { requestedDetailKey = null },
                     widgetNavRequest = requestedNav,
                     onWidgetNavConsumed = { requestedNav = null },
+                    requestedImportUri = requestedImportUri,
+                    onImportConsumed = { requestedImportUri = null },
                 )
             }
         }
@@ -69,6 +78,21 @@ class MainActivity : AppCompatActivity() {
         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/CalendarDataSource.kt

@@ -18,11 +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
 
@@ -48,6 +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
@@ -265,6 +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${span / 1_000L}S"
+    }
+
+    private fun EventStatus.toProviderStatus(): Int = when (this) {
+        EventStatus.Confirmed -> CalendarContract.Events.STATUS_CONFIRMED
+        EventStatus.Tentative -> CalendarContract.Events.STATUS_TENTATIVE
+        EventStatus.Cancelled -> CalendarContract.Events.STATUS_CANCELED
+    }
+
     /** The account a calendar belongs to, for scoping a `Colors` lookup. */
     private fun calendarAccount(calendarId: Long): CalendarAccount? = resolver.query(
         ContentUris.withAppendedId(CalendarContract.Calendars.CONTENT_URI, calendarId),
@@ -316,6 +446,11 @@ class AndroidCalendarDataSource @Inject constructor(
                 CalendarContract.Events.CALENDAR_ID,
                 requireNotNull(form.calendarId) { "EventForm.calendarId is required" },
             )
+            // A globally-unique UID so a later .ics backup/restore can identify
+            // the event and not duplicate it on re-import (the provider leaves
+            // this null for events it didn't sync). Older rows without one fall
+            // back to a stable synthesised UID at export time (deriveIcsUid).
+            put(CalendarContract.Events.UID_2445, "${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)

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

@@ -8,6 +8,8 @@ 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.IcsImportSummary
+import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
@@ -99,6 +101,28 @@ 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, allDayReminderTimeMinutes())
     }

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/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/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
@@ -96,6 +98,7 @@ 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,
@@ -743,14 +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

@@ -98,6 +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
@@ -156,19 +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()

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

@@ -210,6 +210,21 @@ class EventEditViewModel @Inject constructor(
         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

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/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>
@@ -297,4 +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/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>
@@ -294,6 +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/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/test/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImplTest.kt

@@ -445,4 +445,35 @@ class CalendarRepositoryImplTest {
             .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 }

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/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

gradle/libs.versions.toml

@@ -7,7 +7,7 @@ coreKtx = "1.19.0"
 appcompat = "1.7.1"
 lifecycleRuntime = "2.10.0"
 activityCompose = "1.13.0"
-composeBom = "2026.05.01"
+composeBom = "2026.06.00"
 # Material 3 Expressive APIs currently live only in the 1.5 alpha line.
 # Pin explicitly to override the BOM (which ships stable 1.4.0).
 # Re-evaluate when 1.5.0 stable lands.

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",
+    },
+  ],
+}