release: cut v1.3.0 — event edit

Version bumped to 1.3.0 / 11. No code changes beyond the version — 1.3.0 is
the reviewed-and-approved edit slice: shared form for editing, scope-at-save
for recurring events (this / this and following / all, exception rows and
series splits), three-way recurring delete, simple recurrence picker with
weekly weekday toggles, and the stale-instances split fix. CHANGELOG [1.3.0]
carries the details.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.planning/REQUIREMENTS.md

@@ -30,7 +30,10 @@ See full design spec: `docs/superpowers/specs/2026-06-08-calendar-app-design.md`
 - Home-screen widget
 - Full-text search
 - Quick-add
-- Custom notifications/reminders (system already handles these)
+- ~~Custom notifications/reminders (system already handles these)~~ —
+  **reversed:** Calendula targets sole-calendar-app users, so no other app
+  posts reminder notifications. We post them ourselves (Etar model). Planned
+  for v1.4 — see `ROADMAP.md`.
 - Tablet/foldable-specific layouts
 - iOS support (Android-only by design)
 

.planning/ROADMAP.md

@@ -64,9 +64,35 @@ guide here, not a contract — scope per slice is decided as we go.
 | v1.1 | Write foundation — `WRITE_CALENDAR`, read-only-calendar detection, delete (series + single occurrence) | complete (shipped 2026-06-11) |
 | v1.2 | Create event — form, FAB, last-used-calendar preselect | complete (shipped 2026-06-11) |
 | v1.2.1 | Form polish after on-device review — card design system, optional fields + settings defaults, OptionCard dialogs, expressive motion | complete (shipped 2026-06-11) |
-| v1.3 | Edit event — shared form, series edit, reminders, simple recurrence picker | planned |
+| v1.3 | Edit event — shared form, scoped recurring writes (this / following / all), recurrence picker | complete (shipped 2026-06-11) |
+| v1.4 | Reminder notifications — see below | planned |
 | v2.0 | Quick-add, occurrence edit, conflict dialog, polish, release | planned |
 
+## v1.4 — Reminder Notifications
+
+**Essential**, not nice-to-have: Calendula targets users for whom it is their
+*only* calendar app, so reminder delivery can't be delegated to Google/OEM
+Calendar. The calendar provider schedules reminders and broadcasts
+`android.intent.action.EVENT_REMINDER`, but it does **not** post the visible
+notification — a calendar app must. We become that app (the Etar model).
+
+Scope:
+- Manifest-registered `BroadcastReceiver` for `EVENT_REMINDER`
+  (data scheme `content://com.android.calendar`) — wakes us at reminder time,
+  no foreground service.
+- Read `CalendarContract.CalendarAlerts` / `Reminders`, filter to
+  `METHOD_ALERT` / `METHOD_DEFAULT` (skip `METHOD_EMAIL`); post on a dedicated
+  notification channel; tap opens event detail.
+- `POST_NOTIFICATIONS` runtime permission (API 33+) — requested in onboarding.
+- Onboarding step: (a) request `POST_NOTIFICATIONS`, (b) in-app reminders
+  toggle, **default ON**, with copy warning that a second calendar app with
+  notifications on will cause duplicate reminders. Mirrored into Settings
+  (reversible).
+
+Deliberately deferred (add only if needed):
+- Snooze / dismiss notification actions (Etar has them)
+- Battery-optimization exemption prompt for delivery reliability
+
 ## v3.0 — Power-User Features
 
 - Home-screen widget

.planning/STATE.md

@@ -5,11 +5,12 @@
 ## Status
 
 **Milestone:** v2.0 — Write support (milestone 2, in progress)
-**Phase:** v1.2.1 shipped 2026-06-11 — the create-form polish pass after
-Jean-Luc's on-device review (v1.2.0 and v1.1.0 shipped the same day).
-Milestone 2 runs in four slices
-(`docs/superpowers/plans/2026-06-11-03-write-support.md`); next up is v1.3
-(edit event). Note: UI slices now hold release until his explicit approval.
+**Phase:** v1.3.0 (edit event) shipped 2026-06-11 after four on-device
+review rounds (BYDAY toggles, scoped recurring writes, scope-at-save flip,
+stale-instances split bugfix). Milestone 2 runs in four slices
+(`docs/superpowers/plans/2026-06-11-03-write-support.md`); v2.0 (quick-add,
+conflict dialog, polish) is the remaining slice, v1.4 (reminder
+notifications) comes first.
 
 ## Progress
 
@@ -44,8 +45,27 @@ Milestone 2 runs in four slices
   with provider-correct all-day normalisation (UTC midnights, exclusive end),
   domain/mapper/repository tests
 
+- [x] v1.3 edit event (shipped 2026-06-11) — `EventEditScreen` reused for
+  edit (detail-screen Edit action, `canModify`-gated, contextual WRITE
+  upgrade), dirty-checked partial `update` on the Events row (recurring:
+  series DTSTART moves by the user's delta, DURATION instead of DTEND),
+  reminder diff by minutes (kept rows keep their method), simple recurrence
+  picker (FREQ/INTERVAL/UNTIL/COUNT; complex RRULEs preserved verbatim and
+  shown humanized), `EventFormField.Recurrence` incl. settings default,
+  recurrence also available on create; domain/mapper/repository tests.
+  Review round 1: weekly BYDAY day-toggles in the custom picker ("every week
+  on Mon+Fri"). Review rounds 2–4: occurrence edit pulled forward from v2.0
+  and made three-way like delete ("this" = exception row via
+  `CONTENT_EXCEPTION_URI`, "this and following" = series split, "all" =
+  series update); delete equally three-way (truncation via RRULE UNTIL);
+  the edit-scope question moved to save time (Google model) — dirty
+  recurring saves park in `SaveUiState.AwaitingScope`, a changed rule drops
+  the "only this event" option
+
 ## Next
 
-1. v1.3 — edit event: reuse the form, series edit, reminder edit, simple
-   recurrence picker
-2. Monitor the F-Droid build/publish for v1.1.0 / v1.2.0
+1. v1.4 — reminder notifications (essential for sole-app use): `EVENT_REMINDER`
+   receiver + notification channel, `POST_NOTIFICATIONS`, onboarding step with
+   default-on toggle + duplicate-reminder warning (Etar model)
+2. v2.0 — quick-add sheet, conflict dialog, polish pass, milestone release
+3. Monitor the F-Droid build/publish for v1.1.0 – v1.3.0

CHANGELOG.md

@@ -7,6 +7,47 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [1.3.0] — 2026-06-11
+
+### Added
+- Event editing: a pencil action on the detail screen (writable calendars
+  only) opens the event form prefilled with the event. Only fields you
+  actually changed are written back; saving an untouched form is a no-op.
+  Sections holding data are always shown, regardless of the form-field
+  defaults; the calendar itself can't be changed while editing
+- Recurring events — scoped writes, chosen when saving (Google model):
+  "only this event" (a modified-occurrence exception), "this and all
+  following" (the series is split at the occurrence), or "all events in
+  the series". Changing the recurrence rule rules out "only this event"
+- Deleting a recurring event gained the middle option too: "this and all
+  following events" ends the series just before the chosen occurrence
+- Recurrence picker (create and edit): one-tap daily/weekly/monthly/yearly
+  presets plus a custom step with interval + unit, weekday toggles for
+  weekly rules ("every week on Mon and Fri"), and an end condition (never /
+  on a date / after a number of times). Rules the picker can't express
+  (e.g. "second Thursday monthly") are shown humanized and preserved
+  verbatim unless replaced. Recurrence also joined the optional form
+  fields and their settings defaults
+- Validation: a repeat that would end before the event starts is flagged
+  (it would otherwise vanish from every view)
+
+### Changed
+- Editing reminders reconciles against the provider's actual rows:
+  reminders you didn't touch keep their method (e.g. email reminders on
+  synced events survive unrelated edits)
+- The contextual WRITE_CALENDAR upgrade for v1.0 installs covers the edit
+  action like delete
+
+### Fixed
+- Splitting a series ("this and following") sends the complete time-column
+  set in one update, so the provider regenerates its cached instances — an
+  RRULE-only update left a stale duplicate of the tapped occurrence on the
+  split day
+- RRULE UNTIL values are written as the local end of day expressed in UTC
+  (instead of a flat `T235959Z`), so recurrences can't leak an extra day in
+  timezones ahead of UTC
+- `versionName`/`versionCode` bumped to 1.3.0 / 11
+
 ## [1.2.1] — 2026-06-11
 
 ### Added

app/build.gradle.kts

@@ -23,8 +23,8 @@ android {
         applicationId = "de.jeanlucmakiola.calendula"
         minSdk = 29
         targetSdk = 36
-        versionCode = 10
-        versionName = "1.2.1"
+        versionCode = 11
+        versionName = "1.3.0"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }

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

@@ -17,7 +17,9 @@ import de.jeanlucmakiola.calendula.domain.EventDetail
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.domain.Reminder
+import de.jeanlucmakiola.calendula.domain.rruleTruncatedAt
 import java.time.ZoneId
+import java.time.ZoneOffset
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -37,6 +39,44 @@ interface CalendarDataSource {
     /** Insert a new event; returns the new `Events._ID`. */
     fun insertEvent(form: EventForm): Long
 
+    /**
+     * Update an existing event (for recurring events: the whole series) to
+     * match [updated]. [original] is the form as it was prefilled from the
+     * event, so only fields the user actually changed are written and the
+     * reminder rows can be diffed instead of wiped.
+     */
+    fun updateEvent(eventId: Long, original: EventForm, updated: EventForm)
+
+    /**
+     * Change a single occurrence of a recurring event by inserting a
+     * modified-occurrence exception at [beginMillis] (the occurrence's
+     * `Instances.BEGIN`) carrying [form]'s values; returns the exception
+     * row's `Events._ID`.
+     */
+    fun updateOccurrence(eventId: Long, beginMillis: Long, form: EventForm): Long
+
+    /**
+     * Change a recurring event from the occurrence at [beginMillis] onwards
+     * by splitting the series: the existing RRULE ends just before the
+     * occurrence and a new event with [updated]'s values (and rule) starts
+     * there; returns the new event's `Events._ID`. From the first occurrence
+     * this is a plain series update. A carried-over COUNT restarts counting
+     * in the new series (we don't recompute the remaining occurrences).
+     */
+    fun updateEventFromOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        original: EventForm,
+        updated: EventForm,
+    ): Long
+
+    /**
+     * Delete a recurring event from the occurrence at [beginMillis] onwards
+     * by ending the series RRULE just before it. Deleting from the first
+     * occurrence removes the whole event.
+     */
+    fun deleteEventFromOccurrence(eventId: Long, beginMillis: Long)
+
     /** Delete the whole event (for recurring events: the entire series). */
     fun deleteEvent(eventId: Long)
 
@@ -101,7 +141,14 @@ class AndroidCalendarDataSource @Inject constructor(
             put(CalendarContract.Events.TITLE, form.title.trim())
             put(CalendarContract.Events.ALL_DAY, if (form.isAllDay) 1 else 0)
             put(CalendarContract.Events.DTSTART, times.dtStartMillis)
-            put(CalendarContract.Events.DTEND, times.dtEndMillis)
+            // The provider's invariant: recurring rows carry RRULE+DURATION
+            // (and no DTEND), one-off rows carry DTEND.
+            if (form.rrule == null) {
+                put(CalendarContract.Events.DTEND, times.dtEndMillis)
+            } else {
+                put(CalendarContract.Events.RRULE, form.rrule)
+                put(CalendarContract.Events.DURATION, times.toRfc2445Duration(form.isAllDay))
+            }
             put(CalendarContract.Events.EVENT_TIMEZONE, times.timezone)
             put(CalendarContract.Events.AVAILABILITY, form.availability.toProviderValue())
             put(CalendarContract.Events.ACCESS_LEVEL, form.accessLevel.toProviderValue())
@@ -128,6 +175,186 @@ class AndroidCalendarDataSource @Inject constructor(
         return eventId
     }
 
+    override fun updateEvent(eventId: Long, original: EventForm, updated: EventForm) {
+        val values = buildEventUpdateValues(
+            original = original,
+            updated = updated,
+            seriesDtStartMillis = querySeriesRow(eventId).dtStartMillis,
+            zone = ZoneId.systemDefault(),
+        )
+        if (values.isNotEmpty()) {
+            val rows = resolver.update(
+                ContentUris.withAppendedId(CalendarContract.Events.CONTENT_URI, eventId),
+                values.toContentValues(),
+                null, null,
+            )
+            if (rows == 0) throw WriteFailedException("update event id=$eventId")
+        }
+        // Untouched reminder sets are left alone so unrelated edits can't
+        // disturb provider rows the form never knew about.
+        if (updated.reminders.toSet() != original.reminders.toSet()) {
+            reconcileReminders(eventId, updated.reminders)
+        }
+    }
+
+    override fun updateOccurrence(eventId: Long, beginMillis: Long, form: EventForm): Long {
+        // The provider clones the series row and applies these values on top.
+        val values = buildOccurrenceExceptionValues(
+            form = form,
+            originalInstanceMillis = beginMillis,
+            zone = ZoneId.systemDefault(),
+        )
+        val uri = resolver.insert(
+            ContentUris.withAppendedId(CalendarContract.Events.CONTENT_EXCEPTION_URI, eventId),
+            values.toContentValues(),
+        ) ?: throw WriteFailedException("modify occurrence event id=$eventId begin=$beginMillis")
+        val exceptionId = ContentUris.parseId(uri)
+        // Whether the provider copied the parent's reminder rows is its
+        // business — reconciling against the actual rows handles both ways.
+        reconcileReminders(exceptionId, form.reminders)
+        return exceptionId
+    }
+
+    override fun updateEventFromOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        original: EventForm,
+        updated: EventForm,
+    ): Long {
+        val row = querySeriesRow(eventId)
+        // From the first occurrence on (or with no rule to split) this is
+        // just a series update.
+        if (row.rrule.isNullOrBlank() || beginMillis <= row.dtStartMillis) {
+            updateEvent(eventId, original, updated)
+            return eventId
+        }
+        // Insert the new series first: if it fails, the original is untouched.
+        val newEventId = insertEvent(updated)
+        truncateSeries(eventId, row, beginMillis)
+        return newEventId
+    }
+
+    override fun deleteEventFromOccurrence(eventId: Long, beginMillis: Long) {
+        val row = querySeriesRow(eventId)
+        // From the first occurrence on = the whole series; also the fallback
+        // when there is no RRULE to truncate.
+        if (row.rrule.isNullOrBlank() || beginMillis <= row.dtStartMillis) {
+            deleteEvent(eventId)
+            return
+        }
+        truncateSeries(eventId, row, beginMillis)
+    }
+
+    /**
+     * End [row]'s series just before the occurrence at [beginMillis]. The
+     * provider regenerates an event's cached instances only from the values
+     * carried by the update itself — an RRULE-only update leaves the old
+     * instances standing (observed on-device: the truncated occurrence kept
+     * showing) — so the entire time-related set travels together, with only
+     * the RRULE actually changing.
+     */
+    private fun truncateSeries(eventId: Long, row: SeriesRow, beginMillis: Long) {
+        requireNotNull(row.rrule) { "truncateSeries needs a recurring row" }
+        val values = ContentValues().apply {
+            put(CalendarContract.Events.DTSTART, row.dtStartMillis)
+            put(CalendarContract.Events.DURATION, row.duration)
+            put(CalendarContract.Events.EVENT_TIMEZONE, row.timezone)
+            put(CalendarContract.Events.ALL_DAY, row.allDay)
+            put(
+                CalendarContract.Events.RRULE,
+                rruleTruncatedAt(row.rrule, untilUtcMillis = row.truncationCutoff(beginMillis)),
+            )
+        }
+        val rows = resolver.update(
+            ContentUris.withAppendedId(CalendarContract.Events.CONTENT_URI, eventId),
+            values,
+            null, null,
+        )
+        if (rows == 0) {
+            throw WriteFailedException("truncate series event id=$eventId begin=$beginMillis")
+        }
+    }
+
+    /** The series anchor: every time-related column of the Events row. */
+    private fun querySeriesRow(eventId: Long): SeriesRow = resolver.query(
+        ContentUris.withAppendedId(CalendarContract.Events.CONTENT_URI, eventId),
+        arrayOf(
+            CalendarContract.Events.DTSTART,
+            CalendarContract.Events.RRULE,
+            CalendarContract.Events.EVENT_TIMEZONE,
+            CalendarContract.Events.DURATION,
+            CalendarContract.Events.ALL_DAY,
+        ),
+        null, null, null,
+    )?.use { c ->
+        if (c.moveToFirst()) {
+            SeriesRow(
+                dtStartMillis = c.getLong(0),
+                rrule = c.getString(1),
+                timezone = c.getString(2),
+                duration = c.getString(3),
+                allDay = c.getInt(4),
+            )
+        } else {
+            null
+        }
+    } ?: throw WriteFailedException("read series row of event id=$eventId")
+
+    private data class SeriesRow(
+        val dtStartMillis: Long,
+        val rrule: String?,
+        val timezone: String?,
+        val duration: String?,
+        val allDay: Int,
+    ) {
+        /** UNTIL cutoff for ending the series before the occurrence at [beginMillis]. */
+        fun truncationCutoff(beginMillis: Long): Long = previousLocalDayEndUtcMillis(
+            beginMillis = beginMillis,
+            zone = runCatching { ZoneId.of(timezone ?: "UTC") }.getOrDefault(ZoneOffset.UTC),
+        )
+    }
+
+    /**
+     * Make the event's reminder rows match [targetMinutes]: rows with other
+     * lead times are deleted, missing ones inserted as best-effort ALERTs
+     * (like insertEvent). Rows whose minutes survive keep their method.
+     */
+    private fun reconcileReminders(eventId: Long, targetMinutes: List<Int>) {
+        val target = targetMinutes.toSet()
+        val existing = queryReminders(eventId).map { it.minutes }.toSet()
+        (existing - target).forEach { minutes ->
+            resolver.delete(
+                CalendarContract.Reminders.CONTENT_URI,
+                CalendarContract.Reminders.EVENT_ID + " = ? AND " +
+                    CalendarContract.Reminders.MINUTES + " = ?",
+                arrayOf(eventId.toString(), minutes.toString()),
+            )
+        }
+        (target - existing).forEach { minutes ->
+            val reminder = ContentValues().apply {
+                put(CalendarContract.Reminders.EVENT_ID, eventId)
+                put(CalendarContract.Reminders.MINUTES, minutes)
+                put(CalendarContract.Reminders.METHOD, CalendarContract.Reminders.METHOD_ALERT)
+            }
+            if (resolver.insert(CalendarContract.Reminders.CONTENT_URI, reminder) == null) {
+                Log.w(TAG, "Failed to attach reminder ($minutes min) to event $eventId")
+            }
+        }
+    }
+
+    private fun Map<String, Any?>.toContentValues(): ContentValues =
+        ContentValues().also { cv ->
+            forEach { (column, value) ->
+                when (value) {
+                    null -> cv.putNull(column)
+                    is String -> cv.put(column, value)
+                    is Long -> cv.put(column, value)
+                    is Int -> cv.put(column, value)
+                    else -> error("Unsupported value for $column: $value")
+                }
+            }
+        }
+
     override fun deleteEvent(eventId: Long) {
         val deleted = resolver.delete(
             ContentUris.withAppendedId(CalendarContract.Events.CONTENT_URI, eventId),

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

@@ -15,11 +15,37 @@ interface CalendarRepository {
     /** Create a new event from a validated form; returns the new `Events._ID`. */
     suspend fun createEvent(form: EventForm): Long
 
+    /**
+     * Update an event (recurring: the whole series) from a validated form.
+     * [original] is the prefilled form, used to write only what changed.
+     */
+    suspend fun updateEvent(eventId: Long, original: EventForm, updated: EventForm)
+
+    /**
+     * Change a single occurrence of a recurring event (exception row with the
+     * form's values); returns the exception's `Events._ID`.
+     */
+    suspend fun updateOccurrence(eventId: Long, beginMillis: Long, form: EventForm): Long
+
+    /**
+     * Change a recurring event from [beginMillis] onwards (series split);
+     * returns the new event's `Events._ID`.
+     */
+    suspend fun updateEventFromOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        original: EventForm,
+        updated: EventForm,
+    ): Long
+
     /** Delete the whole event (for recurring events: the entire series). */
     suspend fun deleteEvent(eventId: Long)
 
     /** Cancel a single occurrence of a recurring event at its `Instances.BEGIN` time. */
     suspend fun deleteOccurrence(eventId: Long, beginMillis: Long)
+
+    /** Delete a recurring event from the occurrence at [beginMillis] onwards. */
+    suspend fun deleteEventFromOccurrence(eventId: Long, beginMillis: Long)
 }
 
 class NoSuchEventException(eventId: Long) :

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

@@ -74,13 +74,45 @@ class CalendarRepositoryImpl @Inject constructor(
         dataSource.insertEvent(form)
     }
 
+    override suspend fun updateEvent(
+        eventId: Long,
+        original: EventForm,
+        updated: EventForm,
+    ) = withContext(io) {
+        dataSource.updateEvent(eventId, original, updated)
+    }
+
     override suspend fun deleteEvent(eventId: Long) = withContext(io) {
         dataSource.deleteEvent(eventId)
     }
 
+    override suspend fun updateOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        form: EventForm,
+    ): Long = withContext(io) {
+        dataSource.updateOccurrence(eventId, beginMillis, form)
+    }
+
+    override suspend fun updateEventFromOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        original: EventForm,
+        updated: EventForm,
+    ): Long = withContext(io) {
+        dataSource.updateEventFromOccurrence(eventId, beginMillis, original, updated)
+    }
+
     override suspend fun deleteOccurrence(eventId: Long, beginMillis: Long) = withContext(io) {
         dataSource.deleteOccurrence(eventId, beginMillis)
     }
+
+    override suspend fun deleteEventFromOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+    ) = withContext(io) {
+        dataSource.deleteEventFromOccurrence(eventId, beginMillis)
+    }
 }
 
 private fun <T> Flow<Unit>.reQuery(block: suspend () -> T): Flow<T> = flow {

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

@@ -42,8 +42,9 @@ internal fun ColumnReader.toEventDetailCore(
         rawEnd
     }
 
-    val rawTitle = getString(EventDetailProjection.IDX_TITLE)
-    val title = if (rawTitle.isNullOrEmpty()) Fallbacks.UNTITLED_EVENT else rawTitle
+    // Kept raw (no untitled fallback): the detail screen substitutes its own
+    // localized placeholder, and the edit form must prefill the true value.
+    val title = getString(EventDetailProjection.IDX_TITLE).orEmpty()
 
     val color = if (isNull(EventDetailProjection.IDX_EVENT_COLOR)) {
         getInt(EventDetailProjection.IDX_CALENDAR_COLOR)

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

@@ -6,6 +6,7 @@ import de.jeanlucmakiola.calendula.domain.Availability
 import de.jeanlucmakiola.calendula.domain.EventForm
 import kotlinx.datetime.toJavaLocalDate
 import kotlinx.datetime.toJavaLocalDateTime
+import java.time.Instant
 import java.time.ZoneId
 import java.time.ZoneOffset
 
@@ -37,6 +38,118 @@ internal fun EventForm.toWriteTimes(zone: ZoneId): EventWriteTimes = if (isAllDa
     )
 }
 
+/**
+ * RFC 2445 duration for a recurring event's row (the provider requires
+ * DURATION instead of DTEND when an RRULE is set): whole days for all-day
+ * events, seconds otherwise.
+ */
+internal fun EventWriteTimes.toRfc2445Duration(isAllDay: Boolean): String = if (isAllDay) {
+    "P${(dtEndMillis - dtStartMillis) / MILLIS_PER_DAY}D"
+} else {
+    "P${(dtEndMillis - dtStartMillis) / 1_000L}S"
+}
+
+/**
+ * Dirty-checked column values for updating an existing Events row: only what
+ * the user actually changed is written, so untouched fields can't stomp
+ * concurrent external edits. Keys are `CalendarContract.Events` columns; a
+ * null value means "set the column to NULL". An empty map means nothing on
+ * the row changed.
+ *
+ * Time fields travel together (the provider validates them as a unit):
+ * - unchanged times, all-day flag and rrule → no time columns at all;
+ * - non-recurring result → DTSTART/DTEND, DURATION and RRULE cleared;
+ * - recurring result → the *series* DTSTART moves by the same delta the user
+ *   applied to the displayed occurrence ([seriesDtStartMillis] is the row's
+ *   current DTSTART), DURATION replaces DTEND, RRULE is written. This keeps
+ *   past occurrences intact when someone edits a later occurrence's time.
+ */
+internal fun buildEventUpdateValues(
+    original: EventForm,
+    updated: EventForm,
+    seriesDtStartMillis: Long,
+    zone: ZoneId,
+): Map<String, Any?> = buildMap {
+    if (updated.title.trim() != original.title.trim()) {
+        put(CalendarContract.Events.TITLE, updated.title.trim())
+    }
+    if (updated.location.trim() != original.location.trim()) {
+        put(CalendarContract.Events.EVENT_LOCATION, updated.location.trim().ifEmpty { null })
+    }
+    if (updated.description.trim() != original.description.trim()) {
+        put(CalendarContract.Events.DESCRIPTION, updated.description.trim().ifEmpty { null })
+    }
+    if (updated.availability != original.availability) {
+        put(CalendarContract.Events.AVAILABILITY, updated.availability.toProviderValue())
+    }
+    if (updated.accessLevel != original.accessLevel) {
+        put(CalendarContract.Events.ACCESS_LEVEL, updated.accessLevel.toProviderValue())
+    }
+
+    val timesChanged = updated.start != original.start ||
+        updated.end != original.end ||
+        updated.isAllDay != original.isAllDay ||
+        updated.rrule != original.rrule
+    if (!timesChanged) return@buildMap
+
+    val newTimes = updated.toWriteTimes(zone)
+    put(CalendarContract.Events.ALL_DAY, if (updated.isAllDay) 1 else 0)
+    put(CalendarContract.Events.EVENT_TIMEZONE, newTimes.timezone)
+    if (updated.rrule == null) {
+        put(CalendarContract.Events.DTSTART, newTimes.dtStartMillis)
+        put(CalendarContract.Events.DTEND, newTimes.dtEndMillis)
+        put(CalendarContract.Events.RRULE, null)
+        put(CalendarContract.Events.DURATION, null)
+    } else {
+        val startDelta = newTimes.dtStartMillis - original.toWriteTimes(zone).dtStartMillis
+        put(CalendarContract.Events.DTSTART, seriesDtStartMillis + startDelta)
+        put(CalendarContract.Events.DTEND, null)
+        put(CalendarContract.Events.RRULE, updated.rrule)
+        put(CalendarContract.Events.DURATION, newTimes.toRfc2445Duration(updated.isAllDay))
+    }
+}
+
+/**
+ * Column values for a modified-occurrence exception row ("edit only this
+ * event"): inserting them at `Events.CONTENT_EXCEPTION_URI/<id>` makes the
+ * provider clone the series row and apply these on top. Unlike the series
+ * update there is no dirty check — the exception is a fresh row, so every
+ * form-backed column is written (empty optionals as explicit NULLs, since the
+ * clone starts from the parent's values). An exception is a single event:
+ * DTEND, never RRULE/DURATION.
+ */
+internal fun buildOccurrenceExceptionValues(
+    form: EventForm,
+    originalInstanceMillis: Long,
+    zone: ZoneId,
+): Map<String, Any?> = buildMap {
+    val times = form.toWriteTimes(zone)
+    put(CalendarContract.Events.ORIGINAL_INSTANCE_TIME, originalInstanceMillis)
+    put(CalendarContract.Events.TITLE, form.title.trim())
+    put(CalendarContract.Events.ALL_DAY, if (form.isAllDay) 1 else 0)
+    put(CalendarContract.Events.DTSTART, times.dtStartMillis)
+    put(CalendarContract.Events.DTEND, times.dtEndMillis)
+    put(CalendarContract.Events.EVENT_TIMEZONE, times.timezone)
+    put(CalendarContract.Events.AVAILABILITY, form.availability.toProviderValue())
+    put(CalendarContract.Events.ACCESS_LEVEL, form.accessLevel.toProviderValue())
+    put(CalendarContract.Events.EVENT_LOCATION, form.location.trim().ifEmpty { null })
+    put(CalendarContract.Events.DESCRIPTION, form.description.trim().ifEmpty { null })
+}
+
+/**
+ * UTC millis of the last second of the local day *before* the occurrence at
+ * [beginMillis] in [zone] — the cutoff for truncating a series with UNTIL.
+ * The provider's recurrence engine applies UNTIL coarsely (observed on a
+ * Pixel: an occurrence one second *after* UNTIL was still generated), so the
+ * series must end on the previous day, not one second before the occurrence.
+ * With no sub-daily frequencies that is semantically the same cut.
+ */
+internal fun previousLocalDayEndUtcMillis(beginMillis: Long, zone: ZoneId): Long =
+    Instant.ofEpochMilli(beginMillis).atZone(zone).toLocalDate()
+        .atStartOfDay(zone).toInstant().toEpochMilli() - 1_000L
+
+private const val MILLIS_PER_DAY = 86_400_000L
+
 internal fun Availability.toProviderValue(): Int = when (this) {
     Availability.Busy -> CalendarContract.Events.AVAILABILITY_BUSY
     Availability.Free -> CalendarContract.Events.AVAILABILITY_FREE

app/src/main/java/de/jeanlucmakiola/calendula/domain/EventForm.kt

@@ -1,6 +1,11 @@
 package de.jeanlucmakiola.calendula.domain
 
+import kotlinx.datetime.LocalDate
 import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.LocalTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.toLocalDateTime
+import kotlin.time.Instant
 
 /**
  * User input for creating an event (and, from v1.3, editing one). Times are
@@ -19,6 +24,12 @@ data class EventForm(
     val reminders: List<Int> = emptyList(),
     val availability: Availability = Availability.Busy,
     val accessLevel: AccessLevel = AccessLevel.Default,
+    /**
+     * Bare RRULE value (`Events.RRULE` convention, no "RRULE:" prefix); null
+     * means a one-off event. May hold rules the simple picker can't express —
+     * those are kept verbatim until the user picks something else.
+     */
+    val rrule: String? = null,
 )
 
 /**
@@ -29,6 +40,7 @@ enum class EventFormField {
     Location,
     Description,
     Reminders,
+    Recurrence,
     Availability,
     Visibility,
 }
@@ -37,6 +49,8 @@ enum class EventFormProblem {
     /** No target calendar — none picked and no writable calendar exists. */
     NoCalendar,
     EndBeforeStart,
+    /** The recurrence's UNTIL date lies before the event's first day. */
+    RecurrenceEndsBeforeStart,
 }
 
 /**
@@ -44,8 +58,64 @@ enum class EventFormProblem {
  * allowed (display falls back to "(No title)", matching the provider), and a
  * zero-length timed event is allowed (spec §8: instant events exist).
  */
+/**
+ * Prefill the edit form from a loaded event. [beginMillis]/[endMillis] are the
+ * tapped occurrence's own times (`Instances.BEGIN`/`END`), not the series
+ * start — the data layer later turns a time edit into a delta on the series.
+ *
+ * All-day provider times are UTC midnights with an exclusive end; the form
+ * shows the last covered day and keeps placeholder wall-clock times in case
+ * the user switches the event to timed.
+ */
+fun EventDetail.toEditForm(beginMillis: Long, endMillis: Long, zone: TimeZone): EventForm {
+    val (start, end) = if (instance.isAllDay) {
+        val startDate = Instant.fromEpochMilliseconds(beginMillis)
+            .toLocalDateTime(TimeZone.UTC).date
+        val endExclusive = Instant.fromEpochMilliseconds(endMillis)
+            .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 {
+        Instant.fromEpochMilliseconds(beginMillis).toLocalDateTime(zone) to
+            Instant.fromEpochMilliseconds(endMillis).toLocalDateTime(zone)
+    }
+    return EventForm(
+        calendarId = instance.calendarId,
+        title = instance.title,
+        isAllDay = instance.isAllDay,
+        start = start,
+        end = end,
+        location = instance.location.orEmpty(),
+        description = description.orEmpty(),
+        reminders = reminders.map { it.minutes }.distinct().sorted(),
+        availability = availability,
+        accessLevel = accessLevel,
+        rrule = rrule?.removePrefix("RRULE:")?.takeIf { it.isNotBlank() },
+    )
+}
+
+/**
+ * The optional sections that hold a value in [form] — when editing, these
+ * must be visible regardless of the user's default-fields setting, or the
+ * data they carry would be invisible (though still preserved).
+ */
+fun EventForm.populatedFields(): Set<EventFormField> = buildSet {
+    if (location.isNotBlank()) add(EventFormField.Location)
+    if (description.isNotBlank()) add(EventFormField.Description)
+    if (reminders.isNotEmpty()) add(EventFormField.Reminders)
+    if (rrule != null) add(EventFormField.Recurrence)
+    if (availability != Availability.Busy) add(EventFormField.Availability)
+    if (accessLevel != AccessLevel.Default) add(EventFormField.Visibility)
+}
+
 fun EventForm.problems(): Set<EventFormProblem> = buildSet {
     if (calendarId == null) add(EventFormProblem.NoCalendar)
     val endsTooEarly = if (isAllDay) end.date < start.date else end < start
     if (endsTooEarly) add(EventFormProblem.EndBeforeStart)
+    // An UNTIL before the first day would make the provider generate zero
+    // occurrences — the event would silently vanish from every view.
+    val recurrenceEnd = rrule?.let(::parseSimpleRecurrence)?.end
+    if (recurrenceEnd is RecurrenceEnd.Until && recurrenceEnd.date < start.date) {
+        add(EventFormProblem.RecurrenceEndsBeforeStart)
+    }
 }

app/src/main/java/de/jeanlucmakiola/calendula/domain/Models.kt

@@ -115,6 +115,16 @@ enum class AccessLevel {
     Confidential,
 }
 
+/**
+ * How far a write to a recurring event reaches. Non-recurring events always
+ * use [AllEvents] (there is only one).
+ */
+enum class RecurringWriteScope {
+    ThisEvent,
+    ThisAndFollowing,
+    AllEvents,
+}
+
 enum class FailureReason {
     PermissionRevoked,
     NoCalendarsConfigured,

app/src/main/java/de/jeanlucmakiola/calendula/domain/Recurrence.kt

@@ -0,0 +1,197 @@
+package de.jeanlucmakiola.calendula.domain
+
+import kotlinx.datetime.DayOfWeek
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.LocalTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.isoDayNumber
+import kotlinx.datetime.number
+import kotlinx.datetime.toInstant
+import kotlinx.datetime.toLocalDateTime
+import kotlin.time.Instant
+
+/**
+ * The recurrence shapes the simple picker can express (v1.3): a frequency,
+ * an interval, weekly weekday picks, and an optional end. Anything beyond
+ * that (ordinal BYDAY like "2TH", BYMONTHDAY, EXDATE rules, …) stays a raw
+ * RRULE string the picker shows as "custom" and leaves untouched unless the
+ * user replaces it.
+ */
+data class SimpleRecurrence(
+    val freq: RecurrenceFreq,
+    val interval: Int = 1,
+    val end: RecurrenceEnd = RecurrenceEnd.Never,
+    /**
+     * Weekly only: the weekdays the rule fires on (RRULE BYDAY). Empty means
+     * no BYDAY part — the provider derives the day from DTSTART.
+     */
+    val byDays: Set<DayOfWeek> = emptySet(),
+)
+
+enum class RecurrenceFreq {
+    Daily,
+    Weekly,
+    Monthly,
+    Yearly,
+}
+
+sealed interface RecurrenceEnd {
+    data object Never : RecurrenceEnd
+
+    /** Last day on which an occurrence may fall (inclusive). */
+    data class Until(val date: LocalDate) : RecurrenceEnd
+
+    /** Total number of occurrences, counting the first. */
+    data class Count(val times: Int) : RecurrenceEnd
+}
+
+/**
+ * Parse an RRULE into the picker's simple shape, or null when the rule uses
+ * parts the picker can't represent (so the UI preserves the original string).
+ * Accepts an optional leading "RRULE:" and an ignored WKST part. A datetime
+ * UNTIL is converted from UTC into [zone] before its date is taken, mirroring
+ * [toRRule].
+ */
+fun parseSimpleRecurrence(
+    rrule: String,
+    zone: TimeZone = TimeZone.currentSystemDefault(),
+): SimpleRecurrence? {
+    val parts = rrule.removePrefix("RRULE:").split(';')
+        .filter { it.isNotBlank() }
+        .associate { token ->
+            val eq = token.indexOf('=')
+            if (eq <= 0) return null
+            token.substring(0, eq).uppercase() to token.substring(eq + 1)
+        }
+    if (parts.keys.any { it !in setOf("FREQ", "INTERVAL", "UNTIL", "COUNT", "WKST", "BYDAY") }) {
+        return null
+    }
+
+    val freq = when (parts["FREQ"]?.uppercase()) {
+        "DAILY" -> RecurrenceFreq.Daily
+        "WEEKLY" -> RecurrenceFreq.Weekly
+        "MONTHLY" -> RecurrenceFreq.Monthly
+        "YEARLY" -> RecurrenceFreq.Yearly
+        else -> return null
+    }
+    val interval = parts["INTERVAL"]?.let { it.toIntOrNull()?.takeIf { n -> n >= 1 } ?: return null } ?: 1
+
+    // BYDAY is simple only as plain weekday picks on a weekly rule; ordinal
+    // forms ("2TH" = second Thursday) and BYDAY on other frequencies are not.
+    val byDays = parts["BYDAY"]?.let { raw ->
+        if (freq != RecurrenceFreq.Weekly) return null
+        raw.split(',').map { token -> rruleDay(token.trim()) ?: return null }.toSet()
+    } ?: emptySet()
+
+    val until = parts["UNTIL"]
+    val count = parts["COUNT"]
+    if (until != null && count != null) return null
+    val end = when {
+        until != null -> RecurrenceEnd.Until(parseUntilDate(until, zone) ?: return null)
+        count != null -> RecurrenceEnd.Count(count.toIntOrNull()?.takeIf { it >= 1 } ?: return null)
+        else -> RecurrenceEnd.Never
+    }
+    return SimpleRecurrence(freq, interval, end, byDays)
+}
+
+/**
+ * Render as a provider-ready RRULE value (no "RRULE:" prefix —
+ * `CalendarContract.Events.RRULE` stores the bare value). UNTIL is written as
+ * the end of the chosen day *in [zone]*, expressed in UTC: the recurrence
+ * engine has been observed applying UNTIL coarsely after converting it into
+ * the event's timezone, so a plain `T235959Z` can leak one extra day for
+ * zones ahead of UTC.
+ */
+fun SimpleRecurrence.toRRule(zone: TimeZone = TimeZone.currentSystemDefault()): String = buildString {
+    append("FREQ=")
+    append(
+        when (freq) {
+            RecurrenceFreq.Daily -> "DAILY"
+            RecurrenceFreq.Weekly -> "WEEKLY"
+            RecurrenceFreq.Monthly -> "MONTHLY"
+            RecurrenceFreq.Yearly -> "YEARLY"
+        },
+    )
+    if (interval > 1) append(";INTERVAL=$interval")
+    if (freq == RecurrenceFreq.Weekly && byDays.isNotEmpty()) {
+        append(";BYDAY=")
+        append(
+            byDays.sortedBy { it.isoDayNumber }
+                .joinToString(",") { RRULE_DAY_CODES.getValue(it) },
+        )
+    }
+    when (val e = end) {
+        RecurrenceEnd.Never -> Unit
+        is RecurrenceEnd.Until -> {
+            val utc = LocalDateTime(e.date, LocalTime(23, 59, 59))
+                .toInstant(zone)
+                .toLocalDateTime(TimeZone.UTC)
+            append(
+                ";UNTIL=%04d%02d%02dT%02d%02d%02dZ".format(
+                    utc.year, utc.month.number, utc.day,
+                    utc.hour, utc.minute, utc.second,
+                ),
+            )
+        }
+        is RecurrenceEnd.Count -> append(";COUNT=${e.times}")
+    }
+}
+
+private val RRULE_DAY_CODES: Map<DayOfWeek, String> = mapOf(
+    DayOfWeek.MONDAY to "MO",
+    DayOfWeek.TUESDAY to "TU",
+    DayOfWeek.WEDNESDAY to "WE",
+    DayOfWeek.THURSDAY to "TH",
+    DayOfWeek.FRIDAY to "FR",
+    DayOfWeek.SATURDAY to "SA",
+    DayOfWeek.SUNDAY to "SU",
+)
+
+/** Exact two-letter BYDAY token → weekday; ordinal forms ("2TH") return null. */
+private fun rruleDay(token: String): DayOfWeek? =
+    RRULE_DAY_CODES.entries.firstOrNull { it.value == token.uppercase() }?.key
+
+/**
+ * End an arbitrary RRULE (simple or not) at [untilUtcMillis]: any existing
+ * UNTIL/COUNT is dropped, every other part (BYDAY, INTERVAL, …) survives.
+ * Used for "delete this and all following occurrences" — the caller passes a
+ * moment just before the first occurrence to remove.
+ */
+fun rruleTruncatedAt(rrule: String, untilUtcMillis: Long): String {
+    val kept = rrule.removePrefix("RRULE:").split(';')
+        .filter { it.isNotBlank() }
+        .filterNot { part ->
+            val key = part.substringBefore('=').trim().uppercase()
+            key == "UNTIL" || key == "COUNT"
+        }
+    val until = Instant.fromEpochMilliseconds(untilUtcMillis).toLocalDateTime(TimeZone.UTC)
+    val untilPart = "UNTIL=%04d%02d%02dT%02d%02d%02dZ".format(
+        until.year, until.month.number, until.day,
+        until.hour, until.minute, until.second,
+    )
+    return (kept + untilPart).joinToString(";")
+}
+
+/**
+ * Date of an RRULE UNTIL value ("20260801" or "20260801T215959Z"). Datetime
+ * forms are UTC (RFC 5545); the date is taken after converting into [zone] so
+ * a [toRRule]-rendered value round-trips to the day the user picked.
+ */
+private fun parseUntilDate(raw: String, zone: TimeZone): LocalDate? = runCatching {
+    val date = LocalDate(
+        raw.substring(0, 4).toInt(),
+        raw.substring(4, 6).toInt(),
+        raw.substring(6, 8).toInt(),
+    )
+    if (raw.length >= 15 && raw[8] == 'T') {
+        val time = LocalTime(
+            raw.substring(9, 11).toInt(),
+            raw.substring(11, 13).toInt(),
+            raw.substring(13, 15).toInt(),
+        )
+        LocalDateTime(date, time).toInstant(TimeZone.UTC).toLocalDateTime(zone).date
+    } else {
+        date
+    }
+}.getOrNull()

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

@@ -76,6 +76,15 @@ fun CalendarHost(modifier: Modifier = Modifier) {
         createDateIso = date.toString()
     }
 
+    // Edit form (v1.3) — reuses the detail screen's occurrence key; for
+    // recurring events the form itself asks for the write scope at save
+    // time. A saved edit closes the detail screen too: the occurrence the
+    // user tapped may not exist anymore (time moved, recurrence changed), so
+    // falling back to the auto-refreshing calendar is the only honest
+    // destination.
+    var editKey by rememberSaveable { mutableStateOf<LongArray?>(null) }
+    var heldEditKey by remember { mutableStateOf<LongArray?>(null) }
+
     val slideSpec = rememberCalendarSlideSpec()
 
     Box(modifier = modifier.fillMaxSize()) {
@@ -117,6 +126,10 @@ fun CalendarHost(modifier: Modifier = Modifier) {
                     beginMillis = key[1],
                     endMillis = key[2],
                     onBack = { detailKey = null },
+                    onEdit = {
+                        heldEditKey = key
+                        editKey = key
+                    },
                 )
             }
         }
@@ -131,6 +144,26 @@ fun CalendarHost(modifier: Modifier = Modifier) {
                 EventEditScreen(
                     initialDateIso = iso,
                     onClose = { createDateIso = null },
+                    onSaved = { createDateIso = null },
+                )
+            }
+        }
+
+        // Edit form (v1.3) — slides over the detail screen.
+        AnimatedVisibility(
+            visible = editKey != null,
+            enter = slideInHorizontally(slideSpec) { it } + fadeIn(),
+            exit = slideOutHorizontally(slideSpec) { it } + fadeOut(),
+        ) {
+            (editKey ?: heldEditKey)?.let { key ->
+                EventEditScreen(
+                    initialDateIso = null,
+                    editKey = key,
+                    onClose = { editKey = null },
+                    onSaved = {
+                        editKey = null
+                        detailKey = null
+                    },
                 )
             }
         }

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

@@ -0,0 +1,126 @@
+package de.jeanlucmakiola.calendula.ui.common
+
+import android.icu.text.ListFormatter
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.text.AnnotatedString
+import androidx.compose.ui.text.SpanStyle
+import androidx.compose.ui.text.buildAnnotatedString
+import androidx.compose.ui.text.font.FontStyle
+import de.jeanlucmakiola.calendula.R
+import java.time.DayOfWeek
+import java.time.format.DateTimeFormatter
+import java.time.format.FormatStyle
+import java.time.format.TextStyle as JavaTextStyle
+import java.util.Locale
+
+/**
+ * Humanise an RFC 5545 RRULE into a localized phrase, e.g.
+ * "Every week on Tue and Thu until 31 Dec 2026" or "Every day, 10 times".
+ * Falls back to a generic label for rules we don't render in full (ordinal
+ * monthly/yearly BYDAY, etc.). Shared by the detail screen and the edit
+ * form's repeat card.
+ */
+@Composable
+fun recurrenceText(rrule: String, locale: Locale): AnnotatedString {
+    val parts = rrule.removePrefix("RRULE:").split(';').mapNotNull { token ->
+        val eq = token.indexOf('=')
+        if (eq <= 0) null else token.substring(0, eq).uppercase() to token.substring(eq + 1)
+    }.toMap()
+
+    val freq = parts["FREQ"]?.uppercase()
+    val interval = parts["INTERVAL"]?.toIntOrNull() ?: 1
+    val base = when (freq) {
+        "DAILY" -> if (interval == 1) stringResource(R.string.recurrence_daily)
+        else stringResource(R.string.recurrence_every_n_days, interval)
+        "WEEKLY" -> if (interval == 1) stringResource(R.string.recurrence_weekly)
+        else stringResource(R.string.recurrence_every_n_weeks, interval)
+        "MONTHLY" -> if (interval == 1) stringResource(R.string.recurrence_monthly)
+        else stringResource(R.string.recurrence_every_n_months, interval)
+        "YEARLY" -> if (interval == 1) stringResource(R.string.recurrence_yearly)
+        else stringResource(R.string.recurrence_every_n_years, interval)
+        else -> return AnnotatedString(stringResource(R.string.event_detail_recurring))
+    }
+
+    // Weekly + BYDAY → "<base> on <days>"; other BYDAY forms keep just the base.
+    // The day names + their joined block are tracked so only the names (not the
+    // commas/conjunction) can be italicised in the final string.
+    val byDay = parts["BYDAY"]
+    var dayNames: List<String>? = null
+    var joinedDays: String? = null
+    val main = if (freq == "WEEKLY" && !byDay.isNullOrBlank()) {
+        val days = byDay.split(',').mapNotNull { rruleDayName(it.trim(), locale) }
+        if (days.isNotEmpty()) {
+            val joined = ListFormatter.getInstance(locale).format(days)
+            dayNames = days
+            joinedDays = joined
+            stringResource(R.string.recurrence_on_days, base, joined)
+        } else {
+            base
+        }
+    } else {
+        base
+    }
+
+    // End bound: UNTIL (a date) takes precedence over COUNT (a number of times).
+    val until = parts["UNTIL"]?.let { parseUntilDate(it, locale) }
+    val count = parts["COUNT"]?.toIntOrNull()
+    val full = when {
+        until != null -> stringResource(R.string.recurrence_with_until, main, until)
+        count != null -> stringResource(R.string.recurrence_with_count, main, count)
+        else -> main
+    }
+
+    return buildAnnotatedString {
+        append(full)
+        val names = dayNames
+        val joined = joinedDays
+        if (names != null && joined != null) {
+            // Italicise each day name within the joined block only — leaving the
+            // separators and conjunction ("und"/"and") in the regular style.
+            val regionStart = full.indexOf(joined)
+            if (regionStart >= 0) {
+                val regionEnd = regionStart + joined.length
+                var cursor = regionStart
+                for (name in names) {
+                    val at = full.indexOf(name, cursor)
+                    if (at in regionStart until regionEnd) {
+                        addStyle(SpanStyle(fontStyle = FontStyle.Italic), at, at + name.length)
+                        cursor = at + name.length
+                    }
+                }
+            }
+        }
+    }
+}
+
+/** Map an RRULE BYDAY token (e.g. "TU" or "2TH") to a localized short weekday name. */
+private fun rruleDayName(token: String, locale: Locale): String? {
+    val dow = when (token.takeLast(2).uppercase()) {
+        "MO" -> DayOfWeek.MONDAY
+        "TU" -> DayOfWeek.TUESDAY
+        "WE" -> DayOfWeek.WEDNESDAY
+        "TH" -> DayOfWeek.THURSDAY
+        "FR" -> DayOfWeek.FRIDAY
+        "SA" -> DayOfWeek.SATURDAY
+        "SU" -> DayOfWeek.SUNDAY
+        else -> return null
+    }
+    return dow.getDisplayName(JavaTextStyle.SHORT, locale)
+}
+
+/** Parse an RRULE UNTIL value ("20261231" or "20261231T235959Z") to a localized date. */
+private fun parseUntilDate(raw: String, locale: Locale): String? {
+    val digits = raw.takeWhile { it.isDigit() }
+    if (digits.length < 8) return null
+    return try {
+        val date = java.time.LocalDate.of(
+            digits.substring(0, 4).toInt(),
+            digits.substring(4, 6).toInt(),
+            digits.substring(6, 8).toInt(),
+        )
+        DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM).withLocale(locale).format(date)
+    } catch (e: Exception) {
+        null
+    }
+}

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

@@ -5,7 +5,6 @@ import android.content.ActivityNotFoundException
 import android.content.Context
 import android.content.Intent
 import android.content.pm.PackageManager
-import android.icu.text.ListFormatter
 import android.net.Uri
 import androidx.activity.compose.BackHandler
 import androidx.activity.compose.rememberLauncherForActivityResult
@@ -35,6 +34,7 @@ import androidx.compose.material.icons.automirrored.filled.ArrowBack
 import androidx.compose.material.icons.automirrored.filled.Notes
 import androidx.compose.material.icons.filled.CalendarMonth
 import androidx.compose.material.icons.filled.Delete
+import androidx.compose.material.icons.filled.Edit
 import androidx.compose.material.icons.filled.Notifications
 import androidx.compose.material.icons.filled.People
 import androidx.compose.material.icons.filled.Place
@@ -74,7 +74,6 @@ import androidx.compose.ui.text.LinkAnnotation
 import androidx.compose.ui.text.SpanStyle
 import androidx.compose.ui.text.TextLinkStyles
 import androidx.compose.ui.text.buildAnnotatedString
-import androidx.compose.ui.text.font.FontStyle
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextDecoration
 import androidx.compose.ui.unit.Dp
@@ -90,13 +89,14 @@ import de.jeanlucmakiola.calendula.domain.AttendeeType
 import de.jeanlucmakiola.calendula.domain.Availability
 import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.domain.EventStatus
+import de.jeanlucmakiola.calendula.domain.RecurringWriteScope
 import de.jeanlucmakiola.calendula.domain.Reminder
 import de.jeanlucmakiola.calendula.ui.common.CalendarFailure
 import de.jeanlucmakiola.calendula.ui.common.OptionCard
 import de.jeanlucmakiola.calendula.ui.common.currentLocale
 import de.jeanlucmakiola.calendula.ui.common.pastelize
+import de.jeanlucmakiola.calendula.ui.common.recurrenceText
 import kotlinx.datetime.TimeZone
-import java.time.DayOfWeek
 import java.time.ZoneId
 import java.time.format.DateTimeFormatter
 import java.time.format.FormatStyle
@@ -109,7 +109,9 @@ import kotlin.time.Instant
  * Full-screen event detail (spec S4, realised as a navigation destination
  * rather than a bottom sheet — MD3 list→detail pattern). Back gesture and the
  * top-bar arrow both return to the calendar. Events in writable calendars can
- * be deleted from here (v1.1); edit follows in v1.3.
+ * be deleted (v1.1) and edited (v1.3) from here; [onEdit] opens the shared
+ * event form for this occurrence — for recurring events the form asks how
+ * far the change reaches when saving.
  */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
@@ -118,6 +120,7 @@ fun EventDetailScreen(
     beginMillis: Long,
     endMillis: Long,
     onBack: () -> Unit,
+    onEdit: () -> Unit,
     viewModel: EventDetailViewModel = hiltViewModel(),
 ) {
     LaunchedEffect(eventId, beginMillis, endMillis) {
@@ -133,20 +136,35 @@ fun EventDetailScreen(
     var showDeleteDialog by rememberSaveable { mutableStateOf(false) }
 
     // v1.0 installs only hold READ_CALENDAR; the first write asks for the
-    // upgrade in place. Granting continues straight into the confirm dialog.
+    // upgrade in place. Granting continues straight into the tapped action.
+    var pendingEdit by remember { mutableStateOf(false) }
     val writePermissionLauncher = rememberLauncherForActivityResult(
         contract = ActivityResultContracts.RequestPermission(),
     ) { granted ->
-        if (granted) showDeleteDialog = true
+        if (granted) {
+            if (pendingEdit) onEdit() else showDeleteDialog = true
+        }
+        pendingEdit = false
     }
-    val onDeleteClick = {
-        val granted = ContextCompat.checkSelfPermission(
+    val hasWritePermission = {
+        ContextCompat.checkSelfPermission(
             context,
             Manifest.permission.WRITE_CALENDAR,
         ) == PackageManager.PERMISSION_GRANTED
-        if (granted) {
+    }
+    val onDeleteClick = {
+        if (hasWritePermission()) {
             showDeleteDialog = true
         } else {
+            pendingEdit = false
+            writePermissionLauncher.launch(Manifest.permission.WRITE_CALENDAR)
+        }
+    }
+    val onEditClick = {
+        if (hasWritePermission()) {
+            onEdit()
+        } else {
+            pendingEdit = true
             writePermissionLauncher.launch(Manifest.permission.WRITE_CALENDAR)
         }
     }
@@ -189,6 +207,15 @@ fun EventDetailScreen(
                     // birthday calendars etc. are read-only at the provider level.
                     val s = state
                     if (s is EventDetailUiState.Success && s.canModify) {
+                        IconButton(
+                            onClick = onEditClick,
+                            enabled = deleteState != DeleteUiState.Deleting,
+                        ) {
+                            Icon(
+                                imageVector = Icons.Default.Edit,
+                                contentDescription = stringResource(R.string.event_detail_edit),
+                            )
+                        }
                         IconButton(
                             onClick = onDeleteClick,
                             enabled = deleteState != DeleteUiState.Deleting,
@@ -223,9 +250,9 @@ fun EventDetailScreen(
     if (showDeleteDialog && loaded is EventDetailUiState.Success) {
         DeleteEventDialog(
             isRecurring = !loaded.detail.rrule.isNullOrBlank(),
-            onConfirm = { wholeSeries ->
+            onConfirm = { scope ->
                 showDeleteDialog = false
-                viewModel.delete(wholeSeries)
+                viewModel.delete(scope)
             },
             onDismiss = { showDeleteDialog = false },
         )
@@ -234,15 +261,16 @@ fun EventDetailScreen(
 
 /**
  * Delete confirmation. Recurring events choose between cancelling just the
- * tapped occurrence (default) and removing the whole series.
+ * tapped occurrence (default), truncating the series from it onwards, and
+ * removing the whole series.
  */
 @Composable
 private fun DeleteEventDialog(
     isRecurring: Boolean,
-    onConfirm: (wholeSeries: Boolean) -> Unit,
+    onConfirm: (RecurringWriteScope) -> Unit,
     onDismiss: () -> Unit,
 ) {
-    var wholeSeries by rememberSaveable { mutableStateOf(false) }
+    var scope by rememberSaveable { mutableStateOf(RecurringWriteScope.ThisEvent) }
     AlertDialog(
         onDismissRequest = onDismiss,
         title = {
@@ -258,13 +286,18 @@ private fun DeleteEventDialog(
                 Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
                     OptionCard(
                         label = stringResource(R.string.event_delete_option_occurrence),
-                        onClick = { wholeSeries = false },
-                        selected = !wholeSeries,
+                        onClick = { scope = RecurringWriteScope.ThisEvent },
+                        selected = scope == RecurringWriteScope.ThisEvent,
+                    )
+                    OptionCard(
+                        label = stringResource(R.string.event_delete_option_following),
+                        onClick = { scope = RecurringWriteScope.ThisAndFollowing },
+                        selected = scope == RecurringWriteScope.ThisAndFollowing,
                     )
                     OptionCard(
                         label = stringResource(R.string.event_delete_option_series),
-                        onClick = { wholeSeries = true },
-                        selected = wholeSeries,
+                        onClick = { scope = RecurringWriteScope.AllEvents },
+                        selected = scope == RecurringWriteScope.AllEvents,
                     )
                 }
             } else {
@@ -272,7 +305,9 @@ private fun DeleteEventDialog(
             }
         },
         confirmButton = {
-            TextButton(onClick = { onConfirm(if (isRecurring) wholeSeries else true) }) {
+            TextButton(
+                onClick = { onConfirm(if (isRecurring) scope else RecurringWriteScope.AllEvents) },
+            ) {
                 Text(
                     text = stringResource(R.string.event_detail_delete),
                     color = MaterialTheme.colorScheme.error,
@@ -707,116 +742,6 @@ private fun linkifyUrls(text: String, linkColor: Color): AnnotatedString = remem
     }
 }
 
-/**
- * Humanise an RFC 5545 RRULE into a localized phrase, e.g.
- * "Every week on Tue and Thu until 31 Dec 2026" or "Every day, 10 times".
- * Falls back to a generic label for rules we don't render in full (ordinal
- * monthly/yearly BYDAY, etc.).
- */
-@Composable
-private fun recurrenceText(rrule: String, locale: Locale): AnnotatedString {
-    val parts = rrule.removePrefix("RRULE:").split(';').mapNotNull { token ->
-        val eq = token.indexOf('=')
-        if (eq <= 0) null else token.substring(0, eq).uppercase() to token.substring(eq + 1)
-    }.toMap()
-
-    val freq = parts["FREQ"]?.uppercase()
-    val interval = parts["INTERVAL"]?.toIntOrNull() ?: 1
-    val base = when (freq) {
-        "DAILY" -> if (interval == 1) stringResource(R.string.recurrence_daily)
-        else stringResource(R.string.recurrence_every_n_days, interval)
-        "WEEKLY" -> if (interval == 1) stringResource(R.string.recurrence_weekly)
-        else stringResource(R.string.recurrence_every_n_weeks, interval)
-        "MONTHLY" -> if (interval == 1) stringResource(R.string.recurrence_monthly)
-        else stringResource(R.string.recurrence_every_n_months, interval)
-        "YEARLY" -> if (interval == 1) stringResource(R.string.recurrence_yearly)
-        else stringResource(R.string.recurrence_every_n_years, interval)
-        else -> return AnnotatedString(stringResource(R.string.event_detail_recurring))
-    }
-
-    // Weekly + BYDAY → "<base> on <days>"; other BYDAY forms keep just the base.
-    // The day names + their joined block are tracked so only the names (not the
-    // commas/conjunction) can be italicised in the final string.
-    val byDay = parts["BYDAY"]
-    var dayNames: List<String>? = null
-    var joinedDays: String? = null
-    val main = if (freq == "WEEKLY" && !byDay.isNullOrBlank()) {
-        val days = byDay.split(',').mapNotNull { rruleDayName(it.trim(), locale) }
-        if (days.isNotEmpty()) {
-            val joined = ListFormatter.getInstance(locale).format(days)
-            dayNames = days
-            joinedDays = joined
-            stringResource(R.string.recurrence_on_days, base, joined)
-        } else {
-            base
-        }
-    } else {
-        base
-    }
-
-    // End bound: UNTIL (a date) takes precedence over COUNT (a number of times).
-    val until = parts["UNTIL"]?.let { parseUntilDate(it, locale) }
-    val count = parts["COUNT"]?.toIntOrNull()
-    val full = when {
-        until != null -> stringResource(R.string.recurrence_with_until, main, until)
-        count != null -> stringResource(R.string.recurrence_with_count, main, count)
-        else -> main
-    }
-
-    return buildAnnotatedString {
-        append(full)
-        val names = dayNames
-        val joined = joinedDays
-        if (names != null && joined != null) {
-            // Italicise each day name within the joined block only — leaving the
-            // separators and conjunction ("und"/"and") in the regular style.
-            val regionStart = full.indexOf(joined)
-            if (regionStart >= 0) {
-                val regionEnd = regionStart + joined.length
-                var cursor = regionStart
-                for (name in names) {
-                    val at = full.indexOf(name, cursor)
-                    if (at in regionStart until regionEnd) {
-                        addStyle(SpanStyle(fontStyle = FontStyle.Italic), at, at + name.length)
-                        cursor = at + name.length
-                    }
-                }
-            }
-        }
-    }
-}
-
-/** Map an RRULE BYDAY token (e.g. "TU" or "2TH") to a localized short weekday name. */
-private fun rruleDayName(token: String, locale: Locale): String? {
-    val dow = when (token.takeLast(2).uppercase()) {
-        "MO" -> DayOfWeek.MONDAY
-        "TU" -> DayOfWeek.TUESDAY
-        "WE" -> DayOfWeek.WEDNESDAY
-        "TH" -> DayOfWeek.THURSDAY
-        "FR" -> DayOfWeek.FRIDAY
-        "SA" -> DayOfWeek.SATURDAY
-        "SU" -> DayOfWeek.SUNDAY
-        else -> return null
-    }
-    return dow.getDisplayName(JavaTextStyle.SHORT, locale)
-}
-
-/** Parse an RRULE UNTIL value ("20261231" or "20261231T235959Z") to a localized date. */
-private fun parseUntilDate(raw: String, locale: Locale): String? {
-    val digits = raw.takeWhile { it.isDigit() }
-    if (digits.length < 8) return null
-    return try {
-        val date = java.time.LocalDate.of(
-            digits.substring(0, 4).toInt(),
-            digits.substring(4, 6).toInt(),
-            digits.substring(6, 8).toInt(),
-        )
-        DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM).withLocale(locale).format(date)
-    } catch (e: Exception) {
-        null
-    }
-}
-
 /**
  * Format an event's time into a primary line (date, or "All day") and an
  * optional secondary line (time range). Multi-day timed events collapse into a

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

@@ -7,6 +7,7 @@ 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.domain.FailureReason
+import de.jeanlucmakiola.calendula.domain.RecurringWriteScope
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -78,20 +79,23 @@ class EventDetailViewModel @Inject constructor(
     }
 
     /**
-     * Delete the open event. [wholeSeries] is meaningful only for recurring
-     * events: false cancels just the tapped occurrence. Result lands in
-     * [deleteState]; the screen consumes it via [consumeDeleteResult].
+     * Delete the open event. [scope] is meaningful only for recurring events
+     * (one-off events always pass [RecurringWriteScope.AllEvents]). Result
+     * lands in [deleteState]; the screen consumes it via [consumeDeleteResult].
      */
-    fun delete(wholeSeries: Boolean) {
+    fun delete(scope: RecurringWriteScope) {
         val target = _target.value ?: return
         if (_deleteState.value == DeleteUiState.Deleting) return
         viewModelScope.launch {
             _deleteState.value = DeleteUiState.Deleting
             _deleteState.value = try {
-                if (wholeSeries) {
-                    repository.deleteEvent(target.eventId)
-                } else {
-                    repository.deleteOccurrence(target.eventId, target.beginMillis)
+                when (scope) {
+                    RecurringWriteScope.AllEvents ->
+                        repository.deleteEvent(target.eventId)
+                    RecurringWriteScope.ThisEvent ->
+                        repository.deleteOccurrence(target.eventId, target.beginMillis)
+                    RecurringWriteScope.ThisAndFollowing ->
+                        repository.deleteEventFromOccurrence(target.eventId, target.beginMillis)
                 }
                 DeleteUiState.Deleted
             } catch (e: CancellationException) {

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

@@ -27,6 +27,7 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.foundation.text.BasicTextField
 import androidx.compose.foundation.text.KeyboardOptions
@@ -42,6 +43,7 @@ import androidx.compose.material.icons.filled.Lock
 import androidx.compose.material.icons.filled.Notifications
 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.Tune
 import androidx.compose.material.icons.filled.VisibilityOff
@@ -88,6 +90,7 @@ import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.pluralStringResource
 import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.text.AnnotatedString
 import androidx.compose.ui.text.TextStyle
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.input.KeyboardType
@@ -101,49 +104,82 @@ import de.jeanlucmakiola.calendula.domain.Availability
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventFormField
 import de.jeanlucmakiola.calendula.domain.EventFormProblem
+import de.jeanlucmakiola.calendula.domain.RecurrenceEnd
+import de.jeanlucmakiola.calendula.domain.RecurrenceFreq
+import de.jeanlucmakiola.calendula.domain.RecurringWriteScope
+import de.jeanlucmakiola.calendula.domain.SimpleRecurrence
+import de.jeanlucmakiola.calendula.domain.parseSimpleRecurrence
+import de.jeanlucmakiola.calendula.domain.toRRule
 import de.jeanlucmakiola.calendula.ui.common.OptionCard
 import de.jeanlucmakiola.calendula.ui.common.currentLocale
 import de.jeanlucmakiola.calendula.ui.common.pastelize
+import de.jeanlucmakiola.calendula.ui.common.recurrenceText
+import kotlinx.datetime.DayOfWeek
 import kotlinx.datetime.LocalDate
 import kotlinx.datetime.LocalDateTime
 import kotlinx.datetime.LocalTime
 import kotlinx.datetime.TimeZone
+import kotlinx.datetime.isoDayNumber
+import kotlinx.datetime.toJavaDayOfWeek
 import kotlinx.datetime.toJavaLocalDate
+import kotlinx.datetime.toKotlinDayOfWeek
 import kotlinx.datetime.toJavaLocalTime
 import kotlinx.datetime.toLocalDateTime
 import java.time.format.DateTimeFormatter
 import java.time.format.FormatStyle
+import java.time.format.TextStyle as JavaTextStyle
+import java.time.temporal.WeekFields
 import java.util.Locale
 import kotlin.time.Clock
 
 /**
- * Full-screen event form (v1.2: create only). Opens prefilled from the FAB's
- * anchor date; Save validates, writes via the repository, and closes. The
- * calendar picker offers only writable calendars.
+ * Full-screen event form: create (v1.2, from the FAB's anchor date) and edit
+ * (v1.3, [editKey] = eventId + the tapped occurrence's begin/end millis).
+ * Save validates and writes via the repository — a dirty recurring event
+ * first asks how far the change reaches (this occurrence / this and
+ * following / whole series) — then closes. The calendar picker offers only
+ * writable calendars; when editing, the calendar is fixed.
  */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 fun EventEditScreen(
     initialDateIso: String?,
     onClose: () -> Unit,
+    onSaved: () -> Unit,
+    editKey: LongArray? = null,
     viewModel: EventEditViewModel = hiltViewModel(),
 ) {
-    LaunchedEffect(initialDateIso) {
-        val date = initialDateIso?.let { runCatching { LocalDate.parse(it) }.getOrNull() }
-            ?: Clock.System.now().toLocalDateTime(TimeZone.currentSystemDefault()).date
-        viewModel.openNew(date)
+    LaunchedEffect(initialDateIso, editKey) {
+        if (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)
+        }
     }
     val state by viewModel.state.collectAsStateWithLifecycle()
+    val loadFailed by viewModel.loadFailed.collectAsStateWithLifecycle()
 
     // The form is intentionally forgotten on every close (cancel or save) so
-    // the next FAB tap starts clean; it survives rotation because openNew
-    // no-ops while a form is set.
+    // the next open starts clean; it survives rotation because openNew /
+    // openForEdit no-op while a form is set.
     val close = {
         viewModel.reset()
         onClose()
     }
     BackHandler(onBack = close)
 
+    // The event vanished between the detail screen and the edit tap — fall
+    // back to the detail screen, which shows its own failure state.
+    LaunchedEffect(loadFailed) {
+        if (loadFailed) close()
+    }
+
     val context = LocalContext.current
     val snackbarHostState = remember { SnackbarHostState() }
 
@@ -169,7 +205,10 @@ fun EventEditScreen(
     val writeDeniedMessage = stringResource(R.string.event_edit_write_denied)
     LaunchedEffect(state?.saveState) {
         when (state?.saveState) {
-            SaveUiState.Saved -> close()
+            SaveUiState.Saved -> {
+                viewModel.reset()
+                onSaved()
+            }
             SaveUiState.Failed -> {
                 viewModel.consumeSaveResult()
                 snackbarHostState.showSnackbar(saveFailedMessage)
@@ -178,7 +217,7 @@ fun EventEditScreen(
                 viewModel.consumeSaveResult()
                 snackbarHostState.showSnackbar(writeDeniedMessage)
             }
-            SaveUiState.Idle, SaveUiState.Saving, null -> Unit
+            SaveUiState.Idle, SaveUiState.AwaitingScope, SaveUiState.Saving, null -> Unit
         }
     }
 
@@ -222,6 +261,53 @@ fun EventEditScreen(
             )
         }
     }
+
+    if (state?.saveState == SaveUiState.AwaitingScope) {
+        SaveScopeDialog(
+            recurrenceChanged = state?.recurrenceChanged == true,
+            onSelect = viewModel::saveWithScope,
+            onDismiss = viewModel::consumeSaveResult,
+        )
+    }
+}
+
+/**
+ * Scope choice when saving a dirty recurring event: one tap writes just the
+ * tapped occurrence, it and everything after (series split), or the whole
+ * series. A changed recurrence rule rules out the single occurrence — an
+ * exception row can't carry its own rule.
+ */
+@Composable
+private fun SaveScopeDialog(
+    recurrenceChanged: Boolean,
+    onSelect: (RecurringWriteScope) -> Unit,
+    onDismiss: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(stringResource(R.string.event_edit_recurring_title)) },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                if (!recurrenceChanged) {
+                    OptionCard(
+                        label = stringResource(R.string.event_delete_option_occurrence),
+                        onClick = { onSelect(RecurringWriteScope.ThisEvent) },
+                    )
+                }
+                OptionCard(
+                    label = stringResource(R.string.event_delete_option_following),
+                    onClick = { onSelect(RecurringWriteScope.ThisAndFollowing) },
+                )
+                OptionCard(
+                    label = stringResource(R.string.event_delete_option_series),
+                    onClick = { onSelect(RecurringWriteScope.AllEvents) },
+                )
+            }
+        },
+        confirmButton = {
+            TextButton(onClick = onDismiss) { Text(stringResource(R.string.dialog_cancel)) }
+        },
+    )
 }
 
 private enum class PickerTarget { StartDate, StartTime, EndDate, EndTime }
@@ -261,6 +347,7 @@ private fun EventEditContent(
     var picker by remember { mutableStateOf<PickerTarget?>(null) }
     var showCalendarPicker by rememberSaveable { mutableStateOf(false) }
     var showReminderPicker by rememberSaveable { mutableStateOf(false) }
+    var showRecurrencePicker by rememberSaveable { mutableStateOf(false) }
     var showVisibilityPicker by rememberSaveable { mutableStateOf(false) }
     var showFieldPicker by rememberSaveable { mutableStateOf(false) }
 
@@ -348,12 +435,15 @@ private fun EventEditContent(
 
         Spacer(Modifier.height(gap))
 
-        // Calendar card — tap anywhere to pick the target calendar.
+        // Calendar card — tap anywhere to pick the target calendar. Editing
+        // keeps the owning calendar (moving events between calendars is a
+        // sync-adapter minefield; every stock calendar app locks it too).
         EditCard(
             icon = Icons.Default.CalendarMonth,
             iconContentDescription = stringResource(R.string.event_detail_calendar),
             iconTint = accent,
-            onClick = { showCalendarPicker = true }.takeIf { state.calendars.isNotEmpty() },
+            onClick = { showCalendarPicker = true }
+                .takeIf { state.calendars.isNotEmpty() && !state.isEditing },
         ) {
             Text(
                 text = selectedCalendar?.displayName
@@ -438,6 +528,46 @@ private fun EventEditContent(
             }
         }
 
+        OptionalFormSection(visible = EventFormField.Recurrence in state.visibleFields) {
+            Spacer(Modifier.height(gap))
+            EditCard(
+                icon = Icons.Default.Repeat,
+                iconContentDescription = null,
+                onClick = { showRecurrencePicker = true },
+            ) {
+                Row(
+                    verticalAlignment = Alignment.CenterVertically,
+                    modifier = Modifier.fillMaxWidth(),
+                ) {
+                    Column(modifier = Modifier.weight(1f)) {
+                        Text(
+                            text = form.rrule?.let { recurrenceText(it, locale) }
+                                ?: AnnotatedString(stringResource(R.string.event_edit_recurrence_none)),
+                            style = MaterialTheme.typography.titleMedium,
+                        )
+                        Text(
+                            text = stringResource(R.string.event_detail_recurrence),
+                            style = MaterialTheme.typography.bodySmall,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        )
+                    }
+                    Icon(
+                        imageVector = Icons.Default.ArrowDropDown,
+                        contentDescription = null,
+                        tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                }
+                if (EventFormProblem.RecurrenceEndsBeforeStart in state.problems) {
+                    Spacer(Modifier.height(2.dp))
+                    Text(
+                        text = stringResource(R.string.event_edit_error_recurrence_ends_before_start),
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.error,
+                    )
+                }
+            }
+        }
+
         OptionalFormSection(visible = EventFormField.Availability in state.visibleFields) {
             Spacer(Modifier.height(gap))
             EditCard(
@@ -497,7 +627,7 @@ private fun EventEditContent(
             }
         }
 
-        OptionalFormSection(visible = state.hasHiddenFields) {
+        OptionalFormSection(visible = state.hiddenFields.isNotEmpty()) {
             Spacer(Modifier.height(20.dp))
             TextButton(
                 onClick = { showFieldPicker = true },
@@ -561,6 +691,18 @@ private fun EventEditContent(
         )
     }
 
+    if (showRecurrencePicker) {
+        RecurrencePickerDialog(
+            current = form.rrule,
+            startDay = form.start.date.dayOfWeek,
+            onSelect = { rrule ->
+                viewModel.setRecurrence(rrule)
+                showRecurrencePicker = false
+            },
+            onDismiss = { showRecurrencePicker = false },
+        )
+    }
+
     if (showVisibilityPicker) {
         VisibilityPickerDialog(
             selected = form.accessLevel,
@@ -574,7 +716,7 @@ private fun EventEditContent(
 
     if (showFieldPicker) {
         FieldPickerDialog(
-            hiddenFields = EventFormField.entries.filterNot { it in state.visibleFields },
+            hiddenFields = state.hiddenFields,
             onSelect = { field ->
                 viewModel.revealField(field)
                 showFieldPicker = false
@@ -660,71 +802,17 @@ private fun ReminderPickerDialog(
                 }
             } else {
                 Row(verticalAlignment = Alignment.CenterVertically) {
-                    // surfaceContainerHighest — the dialog itself sits on
-                    // surfaceContainerHigh, so anything lower vanishes.
-                    Surface(
-                        color = MaterialTheme.colorScheme.surfaceContainerHighest,
-                        shape = RoundedCornerShape(12.dp),
-                    ) {
-                        InlineField(
-                            value = amountText,
-                            onValueChange = { text ->
-                                if (text.length <= 3 && text.all(Char::isDigit)) {
-                                    amountText = text
-                                }
-                            },
-                            placeholder = "10",
-                            textStyle = MaterialTheme.typography.titleMedium,
-                            keyboardType = KeyboardType.Number,
-                            modifier = Modifier
-                                .width(72.dp)
-                                .padding(horizontal = 14.dp, vertical = 12.dp),
-                        )
-                    }
+                    DialogAmountField(
+                        value = amountText,
+                        onValueChange = { amountText = it },
+                        placeholder = "10",
+                    )
                     Spacer(Modifier.width(12.dp))
-                    var unitMenuOpen by remember { mutableStateOf(false) }
-                    Box {
-                        Surface(
-                            color = MaterialTheme.colorScheme.surfaceContainerHighest,
-                            shape = RoundedCornerShape(12.dp),
-                            onClick = { unitMenuOpen = true },
-                        ) {
-                            Row(
-                                verticalAlignment = Alignment.CenterVertically,
-                                modifier = Modifier.padding(
-                                    start = 14.dp,
-                                    end = 8.dp,
-                                    top = 12.dp,
-                                    bottom = 12.dp,
-                                ),
-                            ) {
-                                Text(
-                                    text = stringResource(reminderUnitLabel(unit)),
-                                    style = MaterialTheme.typography.titleMedium,
-                                )
-                                Spacer(Modifier.width(4.dp))
-                                Icon(
-                                    imageVector = Icons.Default.ArrowDropDown,
-                                    contentDescription = null,
-                                    tint = MaterialTheme.colorScheme.onSurfaceVariant,
-                                )
-                            }
-                        }
-                        DropdownMenu(
-                            expanded = unitMenuOpen,
-                            onDismissRequest = { unitMenuOpen = false },
-                        ) {
-                            ReminderUnit.entries.forEach { entry ->
-                                DropdownMenuItem(
-                                    text = { Text(stringResource(reminderUnitLabel(entry))) },
-                                    onClick = {
-                                        unit = entry
-                                        unitMenuOpen = false
-                                    },
-                                )
-                            }
-                        }
-                    }
+                    DialogUnitDropdown(
+                        label = stringResource(reminderUnitLabel(unit)),
+                        entries = ReminderUnit.entries.map { stringResource(reminderUnitLabel(it)) },
+                        onPick = { unit = ReminderUnit.entries[it] },
+                    )
                 }
             }
         },
@@ -743,6 +831,351 @@ private fun ReminderPickerDialog(
     )
 }
 
+/** How a custom recurrence ends; mirrors [RecurrenceEnd] in saveable form. */
+private enum class RecurrenceEndMode { Never, Until, Count }
+
+/**
+ * Recurrence picker, two steps like the reminder picker: the plain
+ * frequencies as a tappable list (one tap applies and closes), with "Custom"
+ * switching to an interval-plus-unit editor, weekday toggles (weekly only)
+ * and an end condition — only that step needs an OK button. A rule the
+ * simple shape can't express (ordinal BYDAY etc.) stays untouched unless the
+ * user picks something here.
+ */
+@Composable
+private fun RecurrencePickerDialog(
+    current: String?,
+    startDay: DayOfWeek,
+    onSelect: (String?) -> Unit,
+    onDismiss: () -> Unit,
+) {
+    val parsed = remember(current) { current?.let(::parseSimpleRecurrence) }
+    val isPlainPreset = parsed != null && parsed.interval == 1 &&
+        parsed.end == RecurrenceEnd.Never && parsed.byDays.isEmpty()
+    var customMode by rememberSaveable { mutableStateOf(false) }
+    var intervalText by rememberSaveable { mutableStateOf((parsed?.interval ?: 1).toString()) }
+    var freq by rememberSaveable { mutableStateOf(parsed?.freq ?: RecurrenceFreq.Weekly) }
+    // The event's start weekday stands in until the user picks days herself.
+    var daysMask by rememberSaveable {
+        mutableStateOf(
+            (parsed?.byDays?.takeIf { it.isNotEmpty() } ?: setOf(startDay)).toMask(),
+        )
+    }
+    var endMode by rememberSaveable {
+        mutableStateOf(
+            when (parsed?.end) {
+                is RecurrenceEnd.Until -> RecurrenceEndMode.Until
+                is RecurrenceEnd.Count -> RecurrenceEndMode.Count
+                else -> RecurrenceEndMode.Never
+            },
+        )
+    }
+    var untilIso by rememberSaveable {
+        mutableStateOf((parsed?.end as? RecurrenceEnd.Until)?.date?.toString())
+    }
+    var countText by rememberSaveable {
+        mutableStateOf(((parsed?.end as? RecurrenceEnd.Count)?.times ?: 10).toString())
+    }
+    var showUntilPicker by rememberSaveable { mutableStateOf(false) }
+
+    val locale = currentLocale()
+    val untilDate = untilIso?.let { runCatching { LocalDate.parse(it) }.getOrNull() }
+    val interval = intervalText.toIntOrNull()?.takeIf { it in 1..999 }
+    val count = countText.toIntOrNull()?.takeIf { it in 1..999 }
+    val customEnd: RecurrenceEnd? = when (endMode) {
+        RecurrenceEndMode.Never -> RecurrenceEnd.Never
+        RecurrenceEndMode.Until -> untilDate?.let { RecurrenceEnd.Until(it) }
+        RecurrenceEndMode.Count -> count?.let { RecurrenceEnd.Count(it) }
+    }
+    val customResult: String? = if (interval != null && customEnd != null) {
+        SimpleRecurrence(
+            freq = freq,
+            interval = interval,
+            end = customEnd,
+            byDays = if (freq == RecurrenceFreq.Weekly) daysMask.toDaySet() else emptySet(),
+        ).toRRule()
+    } else {
+        null
+    }
+
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(stringResource(R.string.event_detail_recurrence)) },
+        text = {
+            if (!customMode) {
+                Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                    OptionCard(
+                        label = stringResource(R.string.event_edit_recurrence_none),
+                        onClick = { onSelect(null) },
+                        selected = current == null,
+                    )
+                    RecurrenceFreq.entries.forEach { entry ->
+                        OptionCard(
+                            label = stringResource(recurrencePresetLabel(entry)),
+                            onClick = { onSelect(SimpleRecurrence(entry).toRRule()) },
+                            selected = isPlainPreset && parsed?.freq == entry,
+                        )
+                    }
+                    OptionCard(
+                        label = stringResource(R.string.event_edit_recurrence_custom),
+                        onClick = { customMode = true },
+                        selected = current != null && !isPlainPreset,
+                        labelColor = MaterialTheme.colorScheme.primary,
+                    )
+                }
+            } else {
+                Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                    Row(verticalAlignment = Alignment.CenterVertically) {
+                        Text(
+                            text = stringResource(R.string.event_edit_recurrence_every),
+                            style = MaterialTheme.typography.titleMedium,
+                        )
+                        Spacer(Modifier.width(12.dp))
+                        DialogAmountField(
+                            value = intervalText,
+                            onValueChange = { intervalText = it },
+                            placeholder = "1",
+                        )
+                        Spacer(Modifier.width(12.dp))
+                        DialogUnitDropdown(
+                            label = stringResource(recurrenceUnitLabel(freq)),
+                            entries = RecurrenceFreq.entries.map {
+                                stringResource(recurrenceUnitLabel(it))
+                            },
+                            onPick = { freq = RecurrenceFreq.entries[it] },
+                        )
+                    }
+                    if (freq == RecurrenceFreq.Weekly) {
+                        Spacer(Modifier.height(4.dp))
+                        WeekdayToggleRow(
+                            selected = daysMask.toDaySet(),
+                            onToggle = { day -> daysMask = daysMask xor day.toMaskBit() },
+                            locale = locale,
+                        )
+                    }
+                    Spacer(Modifier.height(4.dp))
+                    Text(
+                        text = stringResource(R.string.event_edit_recurrence_ends),
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                    OptionCard(
+                        label = stringResource(R.string.event_edit_recurrence_end_never),
+                        onClick = { endMode = RecurrenceEndMode.Never },
+                        selected = endMode == RecurrenceEndMode.Never,
+                    )
+                    OptionCard(
+                        label = stringResource(R.string.event_edit_recurrence_end_until),
+                        onClick = {
+                            endMode = RecurrenceEndMode.Until
+                            showUntilPicker = true
+                        },
+                        supportingText = untilDate?.let {
+                            remember(it, locale) {
+                                DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM)
+                                    .withLocale(locale).format(it.toJavaLocalDate())
+                            }
+                        },
+                        selected = endMode == RecurrenceEndMode.Until,
+                    )
+                    OptionCard(
+                        label = stringResource(R.string.event_edit_recurrence_end_count),
+                        onClick = { endMode = RecurrenceEndMode.Count },
+                        selected = endMode == RecurrenceEndMode.Count,
+                    )
+                    if (endMode == RecurrenceEndMode.Count) {
+                        Row(verticalAlignment = Alignment.CenterVertically) {
+                            DialogAmountField(
+                                value = countText,
+                                onValueChange = { countText = it },
+                                placeholder = "10",
+                            )
+                            Spacer(Modifier.width(12.dp))
+                            Text(
+                                text = stringResource(R.string.event_edit_recurrence_times),
+                                style = MaterialTheme.typography.titleMedium,
+                            )
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = {
+            // The preset list applies on tap; only the custom step needs OK.
+            if (customMode) {
+                TextButton(
+                    enabled = customResult != null,
+                    onClick = { customResult?.let(onSelect) },
+                ) { Text(stringResource(R.string.dialog_ok)) }
+            }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) { Text(stringResource(R.string.dialog_cancel)) }
+        },
+    )
+
+    if (showUntilPicker) {
+        DatePickerAlert(
+            initial = untilDate ?: LocalDate.fromEpochDays(
+                (Clock.System.now().toEpochMilliseconds() / MILLIS_PER_DAY).toInt(),
+            ),
+            onConfirm = {
+                untilIso = it.toString()
+                showUntilPicker = false
+            },
+            onDismiss = { showUntilPicker = false },
+        )
+    }
+}
+
+/**
+ * One tappable circle per weekday (locale week order), multi-select — the
+ * BYDAY picks of a weekly rule. Deselecting every day is allowed; the rule
+ * then falls back to the event's start weekday (provider behaviour).
+ */
+@Composable
+private fun WeekdayToggleRow(
+    selected: Set<DayOfWeek>,
+    onToggle: (DayOfWeek) -> Unit,
+    locale: Locale,
+) {
+    val days = remember(locale) {
+        val first = WeekFields.of(locale).firstDayOfWeek.toKotlinDayOfWeek()
+        (0 until 7).map { DayOfWeek(((first.isoDayNumber - 1 + it) % 7) + 1) }
+    }
+    Row(
+        horizontalArrangement = Arrangement.SpaceBetween,
+        modifier = Modifier.fillMaxWidth(),
+    ) {
+        days.forEach { day ->
+            val isSelected = day in selected
+            Surface(
+                onClick = { onToggle(day) },
+                shape = CircleShape,
+                color = if (isSelected) {
+                    MaterialTheme.colorScheme.primary
+                } else {
+                    MaterialTheme.colorScheme.surfaceContainerHighest
+                },
+                contentColor = if (isSelected) {
+                    MaterialTheme.colorScheme.onPrimary
+                } else {
+                    MaterialTheme.colorScheme.onSurface
+                },
+                modifier = Modifier.size(36.dp),
+            ) {
+                Box(contentAlignment = Alignment.Center, modifier = Modifier.fillMaxSize()) {
+                    Text(
+                        text = day.toJavaDayOfWeek().getDisplayName(JavaTextStyle.NARROW, locale),
+                        style = MaterialTheme.typography.labelLarge,
+                    )
+                }
+            }
+        }
+    }
+}
+
+/** Weekday sets travel through rememberSaveable as an ISO-day bitmask. */
+private fun DayOfWeek.toMaskBit(): Int = 1 shl (isoDayNumber - 1)
+
+private fun Set<DayOfWeek>.toMask(): Int = fold(0) { acc, day -> acc or day.toMaskBit() }
+
+private fun Int.toDaySet(): Set<DayOfWeek> =
+    DayOfWeek.entries.filter { this and it.toMaskBit() != 0 }.toSet()
+
+/** Tonal 3-digit number input shared by the custom reminder/recurrence steps. */
+@Composable
+private fun DialogAmountField(
+    value: String,
+    onValueChange: (String) -> Unit,
+    placeholder: String,
+) {
+    // surfaceContainerHighest — the dialog itself sits on
+    // surfaceContainerHigh, so anything lower vanishes.
+    Surface(
+        color = MaterialTheme.colorScheme.surfaceContainerHighest,
+        shape = RoundedCornerShape(12.dp),
+    ) {
+        InlineField(
+            value = value,
+            onValueChange = { text ->
+                if (text.length <= 3 && text.all(Char::isDigit)) {
+                    onValueChange(text)
+                }
+            },
+            placeholder = placeholder,
+            textStyle = MaterialTheme.typography.titleMedium,
+            keyboardType = KeyboardType.Number,
+            modifier = Modifier
+                .width(72.dp)
+                .padding(horizontal = 14.dp, vertical = 12.dp),
+        )
+    }
+}
+
+/** Tonal dropdown trigger + menu shared by the custom reminder/recurrence steps. */
+@Composable
+private fun DialogUnitDropdown(
+    label: String,
+    entries: List<String>,
+    onPick: (Int) -> Unit,
+) {
+    var open by remember { mutableStateOf(false) }
+    Box {
+        Surface(
+            color = MaterialTheme.colorScheme.surfaceContainerHighest,
+            shape = RoundedCornerShape(12.dp),
+            onClick = { open = true },
+        ) {
+            Row(
+                verticalAlignment = Alignment.CenterVertically,
+                modifier = Modifier.padding(
+                    start = 14.dp,
+                    end = 8.dp,
+                    top = 12.dp,
+                    bottom = 12.dp,
+                ),
+            ) {
+                Text(
+                    text = label,
+                    style = MaterialTheme.typography.titleMedium,
+                )
+                Spacer(Modifier.width(4.dp))
+                Icon(
+                    imageVector = Icons.Default.ArrowDropDown,
+                    contentDescription = null,
+                    tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                )
+            }
+        }
+        DropdownMenu(expanded = open, onDismissRequest = { open = false }) {
+            entries.forEachIndexed { index, entry ->
+                DropdownMenuItem(
+                    text = { Text(entry) },
+                    onClick = {
+                        onPick(index)
+                        open = false
+                    },
+                )
+            }
+        }
+    }
+}
+
+private fun recurrencePresetLabel(freq: RecurrenceFreq): Int = when (freq) {
+    RecurrenceFreq.Daily -> R.string.recurrence_daily
+    RecurrenceFreq.Weekly -> R.string.recurrence_weekly
+    RecurrenceFreq.Monthly -> R.string.recurrence_monthly
+    RecurrenceFreq.Yearly -> R.string.recurrence_yearly
+}
+
+private fun recurrenceUnitLabel(freq: RecurrenceFreq): Int = when (freq) {
+    RecurrenceFreq.Daily -> R.string.recurrence_unit_days
+    RecurrenceFreq.Weekly -> R.string.recurrence_unit_weeks
+    RecurrenceFreq.Monthly -> R.string.recurrence_unit_months
+    RecurrenceFreq.Yearly -> R.string.recurrence_unit_years
+}
+
 /** One chosen reminder: humanised lead time, remove pinned to the right edge. */
 @Composable
 private fun ReminderRow(label: String, onRemove: () -> Unit) {
@@ -793,6 +1226,7 @@ private fun fieldLabel(field: EventFormField): Int = when (field) {
     EventFormField.Location -> R.string.event_detail_location
     EventFormField.Description -> R.string.event_detail_description
     EventFormField.Reminders -> R.string.event_detail_reminders
+    EventFormField.Recurrence -> R.string.event_detail_recurrence
     EventFormField.Availability -> R.string.event_edit_availability
     EventFormField.Visibility -> R.string.event_edit_visibility
 }
@@ -801,6 +1235,7 @@ private fun fieldIcon(field: EventFormField): ImageVector = when (field) {
     EventFormField.Location -> Icons.Default.Place
     EventFormField.Description -> Icons.AutoMirrored.Filled.Notes
     EventFormField.Reminders -> Icons.Default.Notifications
+    EventFormField.Recurrence -> Icons.Default.Repeat
     EventFormField.Availability -> Icons.Default.EventAvailable
     EventFormField.Visibility -> Icons.Default.Lock
 }

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

@@ -19,13 +19,26 @@ data class EventEditUiState(
     val saveState: SaveUiState,
     /** Optional sections currently rendered (settings defaults ∪ revealed). */
     val visibleFields: Set<EventFormField> = emptySet(),
-    /** True while at least one optional section hides behind "more fields". */
-    val hasHiddenFields: Boolean = false,
+    /**
+     * Optional sections behind "more fields". Sections the current mode can't
+     * offer at all (recurrence while editing a single occurrence) appear in
+     * neither list.
+     */
+    val hiddenFields: List<EventFormField> = emptyList(),
+    /** True while editing an existing event (the calendar is then fixed). */
+    val isEditing: Boolean = false,
+    /**
+     * True while an edit changed the recurrence rule — the save-scope dialog
+     * then drops "only this event" (an exception row can't carry a rule).
+     */
+    val recurrenceChanged: Boolean = false,
 )
 
 /** One-shot state of a save request, mirroring DeleteUiState on the detail screen. */
 sealed interface SaveUiState {
     data object Idle : SaveUiState
+    /** A dirty recurring event waits for the user to pick the write scope. */
+    data object AwaitingScope : SaveUiState
     data object Saving : SaveUiState
     data object Saved : SaveUiState
     /** WRITE_CALENDAR was revoked between the tap and the provider call. */

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

@@ -12,9 +12,13 @@ import de.jeanlucmakiola.calendula.domain.Availability
 import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventFormField
+import de.jeanlucmakiola.calendula.domain.RecurringWriteScope
+import de.jeanlucmakiola.calendula.domain.populatedFields
 import de.jeanlucmakiola.calendula.domain.problems
+import de.jeanlucmakiola.calendula.domain.toEditForm
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.catch
@@ -54,13 +58,32 @@ class EventEditViewModel @Inject constructor(
     // form isn't already shouting errors.
     private val _showProblems = MutableStateFlow(false)
     // Fields added through the "more fields" picker; folds back on reset().
+    // openForEdit seeds it with the sections that already hold values.
     private val _revealed = MutableStateFlow<Set<EventFormField>>(emptySet())
+    // Set while the form edits an existing event instead of composing a new one.
+    private val _editTarget = MutableStateFlow<EditTarget?>(null)
+    private val _loadFailed = MutableStateFlow(false)
+
+    /** True when the event to edit couldn't be loaded; the screen closes itself. */
+    val loadFailed: StateFlow<Boolean> = _loadFailed.asStateFlow()
+
+    /**
+     * The event being edited plus the form exactly as it was prefilled.
+     * For recurring events the write scope is chosen at save time; the
+     * tapped occurrence's [beginMillis] anchors occurrence-level writes.
+     */
+    private data class EditTarget(
+        val eventId: Long,
+        val original: EventForm,
+        val beginMillis: Long,
+    )
 
     private data class LocalInputs(
         val form: EventForm?,
         val saveState: SaveUiState,
         val showProblems: Boolean,
         val revealed: Set<EventFormField>,
+        val editTarget: EditTarget?,
     )
 
     private data class ExternalInputs(
@@ -70,7 +93,7 @@ class EventEditViewModel @Inject constructor(
     )
 
     val state: StateFlow<EventEditUiState?> = combine(
-        combine(_form, _saveState, _showProblems, _revealed, ::LocalInputs),
+        combine(_form, _saveState, _showProblems, _revealed, _editTarget, ::LocalInputs),
         combine(
             repository.calendars()
                 .map { calendars -> calendars.filter { it.canModifyContents } }
@@ -92,7 +115,12 @@ class EventEditViewModel @Inject constructor(
             problems = if (local.showProblems) resolved.problems() else emptySet(),
             saveState = local.saveState,
             visibleFields = visibleFields,
-            hasHiddenFields = visibleFields.size < EventFormField.entries.size,
+            hiddenFields = (EventFormField.entries.toSet() - visibleFields).sorted(),
+            isEditing = local.editTarget != null,
+            // A modified-occurrence exception can't carry its own rule, so
+            // the scope dialog drops "only this event" after a rule change.
+            recurrenceChanged = local.editTarget != null &&
+                resolved.rrule != local.editTarget.original.rrule,
         )
     }
         .flowOn(io)
@@ -123,12 +151,38 @@ class EventEditViewModel @Inject constructor(
         _form.value = EventForm(calendarId = null, start = start, end = end)
     }
 
-    /** Forget the open form; the next [openNew] starts clean. */
+    /**
+     * Load an existing event into the form. [beginMillis]/[endMillis] are the
+     * tapped occurrence's own times, like on the detail screen. No-op while a
+     * form is open, so user edits survive configuration changes.
+     */
+    fun openForEdit(eventId: Long, beginMillis: Long, endMillis: Long) {
+        if (_form.value != null || _editTarget.value != null) return
+        viewModelScope.launch {
+            val detail = try {
+                repository.eventDetail(eventId)
+            } catch (e: CancellationException) {
+                throw e
+            } catch (e: Exception) {
+                _loadFailed.value = true
+                return@launch
+            }
+            val original = detail.toEditForm(beginMillis, endMillis, TimeZone.currentSystemDefault())
+            _editTarget.value = EditTarget(eventId, original, beginMillis)
+            // Sections holding data must show even when not in the defaults.
+            _revealed.value = original.populatedFields()
+            _form.value = original
+        }
+    }
+
+    /** Forget the open form; the next [openNew]/[openForEdit] starts clean. */
     fun reset() {
         _form.value = null
         _saveState.value = SaveUiState.Idle
         _showProblems.value = false
         _revealed.value = emptySet()
+        _editTarget.value = null
+        _loadFailed.value = false
     }
 
     /** Unfold one optional field, picked in the "more fields" dialog. */
@@ -144,6 +198,9 @@ class EventEditViewModel @Inject constructor(
     fun setAvailability(value: Availability) = update { it.copy(availability = value) }
     fun setAccessLevel(value: AccessLevel) = update { it.copy(accessLevel = value) }
 
+    /** Bare RRULE value from the recurrence picker; null = does not repeat. */
+    fun setRecurrence(rrule: String?) = update { it.copy(rrule = rrule) }
+
     fun addReminder(minutes: Int) = update {
         it.copy(reminders = (it.reminders + minutes).distinct().sorted())
     }
@@ -158,7 +215,12 @@ class EventEditViewModel @Inject constructor(
     fun setEndDate(date: LocalDate) = update { it.copy(end = LocalDateTime(date, it.end.time)) }
     fun setEndTime(time: LocalTime) = update { it.copy(end = LocalDateTime(it.end.date, time)) }
 
-    /** Validate and write. Terminal results land in [saveState]. */
+    /**
+     * Validate and write. Saving a dirty recurring event pauses in
+     * [SaveUiState.AwaitingScope] until the screen answers via
+     * [saveWithScope]; everything else writes directly. Terminal results
+     * land in [saveState].
+     */
     fun save() {
         val current = state.value ?: return
         if (current.saveState == SaveUiState.Saving) return
@@ -167,11 +229,49 @@ class EventEditViewModel @Inject constructor(
             _showProblems.value = true
             return
         }
+        val target = _editTarget.value
+        if (target != null && form == target.original) {
+            // A pristine form saves as a no-op instead of a write.
+            _saveState.value = SaveUiState.Saved
+            return
+        }
+        if (target != null && target.original.rrule != null) {
+            _saveState.value = SaveUiState.AwaitingScope
+            return
+        }
+        performSave(form, RecurringWriteScope.AllEvents)
+    }
+
+    /** Finish a save parked in [SaveUiState.AwaitingScope]. */
+    fun saveWithScope(scope: RecurringWriteScope) {
+        val current = state.value ?: return
+        if (current.saveState != SaveUiState.AwaitingScope) return
+        performSave(current.form, scope)
+    }
+
+    private fun performSave(form: EventForm, scope: RecurringWriteScope) {
+        val target = _editTarget.value
         viewModelScope.launch {
             _saveState.value = SaveUiState.Saving
             _saveState.value = try {
-                repository.createEvent(form)
-                prefs.setLastUsedCalendarId(requireNotNull(form.calendarId))
+                if (target == null) {
+                    repository.createEvent(form)
+                    prefs.setLastUsedCalendarId(requireNotNull(form.calendarId))
+                } else {
+                    when (scope) {
+                        RecurringWriteScope.ThisEvent ->
+                            repository.updateOccurrence(target.eventId, target.beginMillis, form)
+                        RecurringWriteScope.ThisAndFollowing ->
+                            repository.updateEventFromOccurrence(
+                                eventId = target.eventId,
+                                beginMillis = target.beginMillis,
+                                original = target.original,
+                                updated = form,
+                            )
+                        RecurringWriteScope.AllEvents ->
+                            repository.updateEvent(target.eventId, target.original, form)
+                    }
+                }
                 SaveUiState.Saved
             } catch (e: CancellationException) {
                 throw e

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

@@ -340,6 +340,7 @@ private fun formFieldLabel(field: EventFormField): Int = when (field) {
     EventFormField.Location -> R.string.event_detail_location
     EventFormField.Description -> R.string.event_detail_description
     EventFormField.Reminders -> R.string.event_detail_reminders
+    EventFormField.Recurrence -> R.string.event_detail_recurrence
     EventFormField.Availability -> R.string.event_edit_availability
     EventFormField.Visibility -> R.string.event_edit_visibility
 }

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

@@ -45,12 +45,15 @@
 
     <!-- Event-Detail-Screen (S4) -->
     <string name="event_detail_back">Zurück</string>
+    <string name="event_detail_edit">Bearbeiten</string>
     <string name="event_detail_delete">Löschen</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>
     <string name="event_delete_option_occurrence">Nur dieser Termin</string>
+    <string name="event_delete_option_following">Dieser und alle folgenden Termine</string>
     <string name="event_delete_option_series">Alle Termine der Serie</string>
+    <string name="event_edit_recurring_title">Wiederkehrenden Termin bearbeiten</string>
     <string name="event_delete_failed">Termin konnte nicht gelöscht werden</string>
     <string name="event_delete_write_denied">Calendula braucht Schreibzugriff, um Termine zu löschen</string>
     <string name="dialog_cancel">Abbrechen</string>
@@ -78,6 +81,21 @@
     <string name="reminder_unit_weeks">Wochen</string>
     <string name="event_edit_availability">Verfügbarkeit</string>
     <string name="event_edit_visibility">Sichtbarkeit</string>
+
+    <!-- Termin-Formular — Wiederholungs-Picker (v1.3) -->
+    <string name="event_edit_recurrence_none">Wiederholt sich nicht</string>
+    <string name="event_edit_recurrence_custom">Benutzerdefiniert</string>
+    <string name="event_edit_recurrence_every">Alle</string>
+    <string name="recurrence_unit_days">Tage</string>
+    <string name="recurrence_unit_weeks">Wochen</string>
+    <string name="recurrence_unit_months">Monate</string>
+    <string name="recurrence_unit_years">Jahre</string>
+    <string name="event_edit_recurrence_ends">Endet</string>
+    <string name="event_edit_recurrence_end_never">Nie</string>
+    <string name="event_edit_recurrence_end_until">An einem Datum</string>
+    <string name="event_edit_recurrence_end_count">Nach einer Anzahl</string>
+    <string name="event_edit_recurrence_times">Mal</string>
+    <string name="event_edit_error_recurrence_ends_before_start">Wiederholung endet vor dem Beginn</string>
     <string name="event_availability_busy">Beschäftigt</string>
     <string name="event_access_default">Standard</string>
     <string name="event_access_public">Öffentlich</string>

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

@@ -46,12 +46,15 @@
 
     <!-- Event detail screen (S4) -->
     <string name="event_detail_back">Back</string>
+    <string name="event_detail_edit">Edit</string>
     <string name="event_detail_delete">Delete</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>
     <string name="event_delete_option_occurrence">Only this event</string>
+    <string name="event_delete_option_following">This and all following events</string>
     <string name="event_delete_option_series">All events in the series</string>
+    <string name="event_edit_recurring_title">Edit recurring event</string>
     <string name="event_delete_failed">Couldn\'t delete the event</string>
     <string name="event_delete_write_denied">Calendula needs write access to delete events</string>
     <string name="dialog_cancel">Cancel</string>
@@ -79,6 +82,21 @@
     <string name="reminder_unit_weeks">weeks</string>
     <string name="event_edit_availability">Availability</string>
     <string name="event_edit_visibility">Visibility</string>
+
+    <!-- Event form — recurrence picker (v1.3) -->
+    <string name="event_edit_recurrence_none">Does not repeat</string>
+    <string name="event_edit_recurrence_custom">Custom</string>
+    <string name="event_edit_recurrence_every">Every</string>
+    <string name="recurrence_unit_days">days</string>
+    <string name="recurrence_unit_weeks">weeks</string>
+    <string name="recurrence_unit_months">months</string>
+    <string name="recurrence_unit_years">years</string>
+    <string name="event_edit_recurrence_ends">Ends</string>
+    <string name="event_edit_recurrence_end_never">Never</string>
+    <string name="event_edit_recurrence_end_until">On a date</string>
+    <string name="event_edit_recurrence_end_count">After a number of times</string>
+    <string name="event_edit_recurrence_times">times</string>
+    <string name="event_edit_error_recurrence_ends_before_start">Repeats end before the event starts</string>
     <string name="event_availability_busy">Busy</string>
     <string name="event_access_default">Default</string>
     <string name="event_access_public">Public</string>

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

@@ -198,6 +198,43 @@ class CalendarRepositoryImplTest {
         }
     }
 
+    @Test
+    fun `updateEvent forwards id and both forms`(@TempDir tempDir: Path) = runTest {
+        val fake = FakeCalendarDataSource()
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val original = EventForm(
+            calendarId = 1L,
+            title = "Stand-up",
+            start = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(9, 0)),
+            end = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(9, 15)),
+        )
+        val updated = original.copy(title = "Daily")
+
+        repo.updateEvent(eventId = 42L, original = original, updated = updated)
+
+        assertThat(fake.updatedEvents).containsExactly(Triple(42L, original, updated))
+    }
+
+    @Test
+    fun `updateEvent propagates write failures`(@TempDir tempDir: Path) = runTest {
+        val fake = FakeCalendarDataSource().apply {
+            writeError = WriteFailedException("update event id=42")
+        }
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val form = EventForm(
+            calendarId = 1L,
+            start = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(9, 0)),
+            end = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(10, 0)),
+        )
+
+        try {
+            repo.updateEvent(eventId = 42L, original = form, updated = form.copy(title = "X"))
+            error("Expected WriteFailedException")
+        } catch (expected: WriteFailedException) {
+            assertThat(expected.message).contains("42")
+        }
+    }
+
     @Test
     fun `deleteEvent delegates to the data source`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource()
@@ -220,6 +257,61 @@ class CalendarRepositoryImplTest {
         assertThat(fake.deletedEventIds).isEmpty()
     }
 
+    @Test
+    fun `deleteEventFromOccurrence forwards event id and begin time`(@TempDir tempDir: Path) = runTest {
+        val fake = FakeCalendarDataSource()
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+
+        repo.deleteEventFromOccurrence(eventId = 42L, beginMillis = 1_000L)
+
+        assertThat(fake.deletedFromOccurrences).containsExactly(42L to 1_000L)
+        assertThat(fake.deletedEventIds).isEmpty()
+        assertThat(fake.deletedOccurrences).isEmpty()
+    }
+
+    @Test
+    fun `updateOccurrence forwards target and form, returns the exception id`(@TempDir tempDir: Path) = runTest {
+        val fake = FakeCalendarDataSource().apply { nextInsertId = 88L }
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val form = EventForm(
+            calendarId = 1L,
+            title = "Moved",
+            start = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(9, 0)),
+            end = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(10, 0)),
+        )
+
+        val id = repo.updateOccurrence(eventId = 42L, beginMillis = 1_000L, form = form)
+
+        assertThat(id).isEqualTo(88L)
+        assertThat(fake.updatedOccurrences).containsExactly(Triple(42L, 1_000L, form))
+        assertThat(fake.updatedEvents).isEmpty()
+    }
+
+    @Test
+    fun `updateEventFromOccurrence forwards target and forms, returns the new id`(@TempDir tempDir: Path) = runTest {
+        val fake = FakeCalendarDataSource().apply { nextInsertId = 99L }
+        val repo = CalendarRepositoryImpl(fake, newPrefs(tempDir), Dispatchers.Unconfined)
+        val original = EventForm(
+            calendarId = 1L,
+            title = "Weekly",
+            start = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(9, 0)),
+            end = LocalDateTime(LocalDate(2026, 6, 12), LocalTime(10, 0)),
+            rrule = "FREQ=WEEKLY",
+        )
+        val updated = original.copy(title = "Weekly, renamed")
+
+        val id = repo.updateEventFromOccurrence(
+            eventId = 42L,
+            beginMillis = 1_000L,
+            original = original,
+            updated = updated,
+        )
+
+        assertThat(id).isEqualTo(99L)
+        assertThat(fake.updatedFromOccurrences).containsExactly(Triple(42L, 1_000L, updated))
+        assertThat(fake.updatedEvents).isEmpty()
+    }
+
     @Test
     fun `deleteEvent propagates write failures`(@TempDir tempDir: Path) = runTest {
         val fake = FakeCalendarDataSource().apply {

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

@@ -88,6 +88,12 @@ class EventDetailMapperTest {
         assertThat(detail.attendees).isEmpty()
     }
 
+    @Test
+    fun `missing title stays raw so the edit form does not inherit a placeholder`() {
+        assertThat(detailReader(title = null).toDetail()!!.instance.title).isEmpty()
+        assertThat(detailReader(title = "").toDetail()!!.instance.title).isEmpty()
+    }
+
     @Test
     fun `event color falls back to calendar color when null`() {
         val detail = detailReader(eventColor = null, calendarColor = 0xFF112233.toInt())

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

@@ -71,4 +71,151 @@ class EventWriteMapperTest {
         // 11th, 12th, 13th inclusive = 3 days.
         assertThat(times.dtEndMillis - times.dtStartMillis).isEqualTo(3L * 86_400_000L)
     }
+
+    @Test
+    fun `truncation cutoff is the end of the previous local day`() {
+        // June 9 2026 15:30Z == 17:30 in Berlin. The cutoff must be
+        // June 8 23:59:59 Berlin == June 8 21:59:59Z.
+        assertThat(previousLocalDayEndUtcMillis(1_781_019_000_000L, berlin))
+            .isEqualTo(1_780_955_999_000L)
+        // All-day series live in UTC: the cutoff for a June 9 UTC-midnight
+        // occurrence is June 8 23:59:59Z.
+        assertThat(previousLocalDayEndUtcMillis(1_780_963_200_000L, ZoneId.of("UTC")))
+            .isEqualTo(1_780_963_199_000L)
+    }
+
+    @Test
+    fun `duration renders seconds for timed and days for all-day events`() {
+        assertThat(form().toWriteTimes(berlin).toRfc2445Duration(isAllDay = false))
+            .isEqualTo("P5400S")
+        assertThat(form(isAllDay = true).toWriteTimes(berlin).toRfc2445Duration(isAllDay = true))
+            .isEqualTo("P1D")
+    }
+
+    // --- buildEventUpdateValues (dirty-checked partial update) ---
+
+    private val seriesStart = 1_700_000_000_000L
+
+    private fun update(original: EventForm, updated: EventForm): Map<String, Any?> =
+        buildEventUpdateValues(original, updated, seriesStart, berlin)
+
+    @Test
+    fun `pristine form produces no values`() {
+        val original = form()
+        assertThat(update(original, original.copy())).isEmpty()
+    }
+
+    @Test
+    fun `text-only edit writes just the changed columns`() {
+        val original = form()
+        val values = update(original, original.copy(title = "New", description = "Body"))
+        assertThat(values).containsExactly(
+            CalendarContract.Events.TITLE, "New",
+            CalendarContract.Events.DESCRIPTION, "Body",
+        )
+    }
+
+    @Test
+    fun `clearing location writes an explicit null`() {
+        val original = form().copy(location = "Berlin")
+        val values = update(original, original.copy(location = " "))
+        assertThat(values).containsExactly(CalendarContract.Events.EVENT_LOCATION, null)
+    }
+
+    @Test
+    fun `time edit on a one-off event writes absolute times and clears recurrence columns`() {
+        val original = form()
+        val updated = original.copy(
+            start = LocalDateTime(LocalDate(2026, 6, 11), LocalTime(11, 0)),
+            end = LocalDateTime(LocalDate(2026, 6, 11), LocalTime(12, 0)),
+        )
+        val values = update(original, updated)
+        // 2026-06-11 11:00 CEST == 09:00Z.
+        assertThat(values[CalendarContract.Events.DTSTART])
+            .isEqualTo(1_781_164_800_000L + 3_600_000L)
+        assertThat(values[CalendarContract.Events.DTEND])
+            .isEqualTo(1_781_164_800_000L + 2L * 3_600_000L)
+        assertThat(values).containsEntry(CalendarContract.Events.RRULE, null)
+        assertThat(values).containsEntry(CalendarContract.Events.DURATION, null)
+        assertThat(values[CalendarContract.Events.EVENT_TIMEZONE]).isEqualTo("Europe/Berlin")
+        assertThat(values[CalendarContract.Events.ALL_DAY]).isEqualTo(0)
+    }
+
+    @Test
+    fun `time edit on a recurring event moves the series start by the same delta`() {
+        val original = form().copy(rrule = "FREQ=WEEKLY")
+        val updated = original.copy(
+            // Pushed one hour later than the displayed occurrence.
+            start = LocalDateTime(LocalDate(2026, 6, 11), LocalTime(11, 0)),
+            end = LocalDateTime(LocalDate(2026, 6, 11), LocalTime(12, 30)),
+        )
+        val values = update(original, updated)
+        assertThat(values[CalendarContract.Events.DTSTART]).isEqualTo(seriesStart + 3_600_000L)
+        assertThat(values).containsEntry(CalendarContract.Events.DTEND, null)
+        assertThat(values[CalendarContract.Events.RRULE]).isEqualTo("FREQ=WEEKLY")
+        assertThat(values[CalendarContract.Events.DURATION]).isEqualTo("P5400S")
+    }
+
+    @Test
+    fun `adding a recurrence keeps the times and writes rule plus duration`() {
+        val original = form()
+        val values = update(original, original.copy(rrule = "FREQ=DAILY;COUNT=5"))
+        // The event was one-off, so the row's DTSTART is the occurrence start
+        // and a zero delta keeps it in place.
+        assertThat(values[CalendarContract.Events.DTSTART]).isEqualTo(seriesStart)
+        assertThat(values[CalendarContract.Events.RRULE]).isEqualTo("FREQ=DAILY;COUNT=5")
+        assertThat(values[CalendarContract.Events.DURATION]).isEqualTo("P5400S")
+        assertThat(values).containsEntry(CalendarContract.Events.DTEND, null)
+    }
+
+    @Test
+    fun `removing the recurrence writes absolute occurrence times and clears the rule`() {
+        val original = form().copy(rrule = "FREQ=WEEKLY")
+        val values = update(original, original.copy(rrule = null))
+        assertThat(values[CalendarContract.Events.DTSTART]).isEqualTo(1_781_164_800_000L)
+        assertThat(values[CalendarContract.Events.DTEND])
+            .isEqualTo(1_781_164_800_000L + 5_400_000L)
+        assertThat(values).containsEntry(CalendarContract.Events.RRULE, null)
+        assertThat(values).containsEntry(CalendarContract.Events.DURATION, null)
+    }
+
+    @Test
+    fun `reminder-only changes touch no event columns`() {
+        val original = form()
+        assertThat(update(original, original.copy(reminders = listOf(10)))).isEmpty()
+    }
+
+    // --- buildOccurrenceExceptionValues ("edit only this event") ---
+
+    @Test
+    fun `occurrence exception carries absolute times and the original instance`() {
+        val values = buildOccurrenceExceptionValues(
+            form = form().copy(title = "Moved", location = "Berlin"),
+            originalInstanceMillis = 1_700_000_000_000L,
+            zone = berlin,
+        )
+        assertThat(values[CalendarContract.Events.ORIGINAL_INSTANCE_TIME])
+            .isEqualTo(1_700_000_000_000L)
+        assertThat(values[CalendarContract.Events.TITLE]).isEqualTo("Moved")
+        assertThat(values[CalendarContract.Events.EVENT_LOCATION]).isEqualTo("Berlin")
+        assertThat(values[CalendarContract.Events.DTSTART]).isEqualTo(1_781_164_800_000L)
+        assertThat(values[CalendarContract.Events.DTEND])
+            .isEqualTo(1_781_164_800_000L + 5_400_000L)
+        // A single occurrence never carries its own rule.
+        assertThat(values).doesNotContainKey(CalendarContract.Events.RRULE)
+        assertThat(values).doesNotContainKey(CalendarContract.Events.DURATION)
+    }
+
+    @Test
+    fun `occurrence exception clears empty optionals explicitly`() {
+        // The provider clones the parent row, so a blank field must be an
+        // explicit NULL or the parent's value would survive.
+        val values = buildOccurrenceExceptionValues(
+            form = form(),
+            originalInstanceMillis = 0L,
+            zone = berlin,
+        )
+        assertThat(values).containsEntry(CalendarContract.Events.EVENT_LOCATION, null)
+        assertThat(values).containsEntry(CalendarContract.Events.DESCRIPTION, null)
+    }
 }

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

@@ -20,8 +20,12 @@ internal class FakeCalendarDataSource : CalendarDataSource {
     var nextInsertId: Long = 100L
 
     val insertedForms = mutableListOf<EventForm>()
+    val updatedEvents = mutableListOf<Triple<Long, EventForm, EventForm>>()
+    val updatedOccurrences = mutableListOf<Triple<Long, Long, EventForm>>()
+    val updatedFromOccurrences = mutableListOf<Triple<Long, Long, EventForm>>()
     val deletedEventIds = mutableListOf<Long>()
     val deletedOccurrences = mutableListOf<Pair<Long, Long>>()
+    val deletedFromOccurrences = mutableListOf<Pair<Long, Long>>()
 
     private val listeners = mutableListOf<() -> Unit>()
 
@@ -36,6 +40,33 @@ internal class FakeCalendarDataSource : CalendarDataSource {
         return nextInsertId
     }
 
+    override fun updateEvent(eventId: Long, original: EventForm, updated: EventForm) {
+        writeError?.let { throw it }
+        updatedEvents += Triple(eventId, original, updated)
+    }
+
+    override fun updateOccurrence(eventId: Long, beginMillis: Long, form: EventForm): Long {
+        writeError?.let { throw it }
+        updatedOccurrences += Triple(eventId, beginMillis, form)
+        return nextInsertId
+    }
+
+    override fun updateEventFromOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        original: EventForm,
+        updated: EventForm,
+    ): Long {
+        writeError?.let { throw it }
+        updatedFromOccurrences += Triple(eventId, beginMillis, updated)
+        return nextInsertId
+    }
+
+    override fun deleteEventFromOccurrence(eventId: Long, beginMillis: Long) {
+        writeError?.let { throw it }
+        deletedFromOccurrences += eventId to beginMillis
+    }
+
     override fun deleteEvent(eventId: Long) {
         writeError?.let { throw it }
         deletedEventIds += eventId

app/src/test/java/de/jeanlucmakiola/calendula/domain/EventFormTest.kt

@@ -4,7 +4,9 @@ import com.google.common.truth.Truth.assertThat
 import kotlinx.datetime.LocalDate
 import kotlinx.datetime.LocalDateTime
 import kotlinx.datetime.LocalTime
+import kotlinx.datetime.TimeZone
 import org.junit.jupiter.api.Test
+import kotlin.time.Instant
 
 class EventFormTest {
 
@@ -69,4 +71,132 @@ class EventFormTest {
             EventFormProblem.EndBeforeStart,
         )
     }
+
+    @Test
+    fun `recurrence until before the first day is a problem`() {
+        // Days before the start, so it parses to an earlier date in any zone.
+        val bad = form().copy(rrule = "FREQ=DAILY;UNTIL=20260601T120000Z")
+        assertThat(bad.problems())
+            .containsExactly(EventFormProblem.RecurrenceEndsBeforeStart)
+    }
+
+    @Test
+    fun `recurrence until on or after the first day is fine`() {
+        // Date-only UNTIL parses zone-independently.
+        assertThat(form().copy(rrule = "FREQ=DAILY;UNTIL=20260611").problems()).isEmpty()
+        assertThat(form().copy(rrule = "FREQ=WEEKLY").problems()).isEmpty()
+    }
+
+    @Test
+    fun `complex rrules are not validated against the start`() {
+        // The picker can't have produced this ("second Monday" ordinal BYDAY);
+        // it is preserved verbatim and never flagged.
+        assertThat(form().copy(rrule = "FREQ=MONTHLY;BYDAY=2MO;UNTIL=20200101").problems()).isEmpty()
+    }
+
+    @Test
+    fun `weekly byday rules are validated against the start`() {
+        val bad = form().copy(rrule = "FREQ=WEEKLY;BYDAY=MO,FR;UNTIL=20200101")
+        assertThat(bad.problems())
+            .containsExactly(EventFormProblem.RecurrenceEndsBeforeStart)
+    }
+
+    private val berlin = TimeZone.of("Europe/Berlin")
+
+    private fun detail(
+        isAllDay: Boolean = false,
+        title: String = "Stand-up",
+        location: String? = "Berlin",
+        description: String? = "Body",
+        rrule: String? = null,
+        reminders: List<Reminder> = emptyList(),
+        availability: Availability = Availability.Busy,
+        accessLevel: AccessLevel = AccessLevel.Default,
+    ): EventDetail = EventDetail(
+        instance = EventInstance(
+            instanceId = 1L,
+            eventId = 1L,
+            calendarId = 7L,
+            title = title,
+            start = Instant.fromEpochMilliseconds(0L),
+            end = Instant.fromEpochMilliseconds(0L),
+            isAllDay = isAllDay,
+            color = 0,
+            location = location,
+        ),
+        description = description,
+        organizer = null,
+        attendees = emptyList(),
+        rrule = rrule,
+        reminders = reminders,
+        availability = availability,
+        accessLevel = accessLevel,
+    )
+
+    @Test
+    fun `toEditForm prefills a timed event from the occurrence times`() {
+        // 2026-06-11 is CEST (UTC+2): 08:00Z == 10:00 local.
+        val prefilled = detail().toEditForm(
+            beginMillis = 1_781_164_800_000L,
+            endMillis = 1_781_164_800_000L + 90L * 60L * 1000L,
+            zone = berlin,
+        )
+        assertThat(prefilled.start).isEqualTo(LocalDateTime(LocalDate(2026, 6, 11), LocalTime(10, 0)))
+        assertThat(prefilled.end).isEqualTo(LocalDateTime(LocalDate(2026, 6, 11), LocalTime(11, 30)))
+        assertThat(prefilled.isAllDay).isFalse()
+        assertThat(prefilled.calendarId).isEqualTo(7L)
+        assertThat(prefilled.title).isEqualTo("Stand-up")
+        assertThat(prefilled.location).isEqualTo("Berlin")
+        assertThat(prefilled.description).isEqualTo("Body")
+    }
+
+    @Test
+    fun `toEditForm turns the exclusive all-day end into the last covered day`() {
+        // 11th..13th = UTC midnights of the 11th and the (exclusive) 14th.
+        val prefilled = detail(isAllDay = true).toEditForm(
+            beginMillis = LocalDate(2026, 6, 11).toEpochDays() * 86_400_000L,
+            endMillis = LocalDate(2026, 6, 14).toEpochDays() * 86_400_000L,
+            zone = berlin,
+        )
+        assertThat(prefilled.start.date).isEqualTo(LocalDate(2026, 6, 11))
+        assertThat(prefilled.end.date).isEqualTo(LocalDate(2026, 6, 13))
+        assertThat(prefilled.isAllDay).isTrue()
+    }
+
+    @Test
+    fun `toEditForm sorts and dedupes reminder minutes and strips an RRULE prefix`() {
+        val prefilled = detail(
+            rrule = "RRULE:FREQ=WEEKLY",
+            reminders = listOf(
+                Reminder(30, ReminderMethod.Email),
+                Reminder(10, ReminderMethod.Alert),
+                Reminder(30, ReminderMethod.Alert),
+            ),
+        ).toEditForm(beginMillis = 0L, endMillis = 3_600_000L, zone = berlin)
+        assertThat(prefilled.reminders).containsExactly(10, 30).inOrder()
+        assertThat(prefilled.rrule).isEqualTo("FREQ=WEEKLY")
+    }
+
+    @Test
+    fun `populatedFields reports exactly the sections holding values`() {
+        val empty = form().copy(location = "", description = "")
+        assertThat(empty.populatedFields()).isEmpty()
+
+        val full = form().copy(
+            location = "Berlin",
+            description = "Body",
+            reminders = listOf(10),
+            rrule = "FREQ=DAILY",
+            availability = Availability.Free,
+            accessLevel = AccessLevel.Private,
+        )
+        assertThat(full.populatedFields()).containsExactly(
+            EventFormField.Location,
+            EventFormField.Description,
+            EventFormField.Reminders,
+            EventFormField.Recurrence,
+            EventFormField.Availability,
+            EventFormField.Visibility,
+        )
+    }
 }

app/src/test/java/de/jeanlucmakiola/calendula/domain/RecurrenceTest.kt

@@ -0,0 +1,164 @@
+package de.jeanlucmakiola.calendula.domain
+
+import com.google.common.truth.Truth.assertThat
+import kotlinx.datetime.DayOfWeek
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.TimeZone
+import org.junit.jupiter.api.Test
+
+class RecurrenceTest {
+
+    private val utc = TimeZone.UTC
+    private val berlin = TimeZone.of("Europe/Berlin")
+
+    @Test
+    fun `plain frequency parses with defaults`() {
+        assertThat(parseSimpleRecurrence("FREQ=WEEKLY"))
+            .isEqualTo(SimpleRecurrence(RecurrenceFreq.Weekly))
+        assertThat(parseSimpleRecurrence("FREQ=DAILY"))
+            .isEqualTo(SimpleRecurrence(RecurrenceFreq.Daily))
+    }
+
+    @Test
+    fun `leading RRULE prefix and WKST are tolerated`() {
+        assertThat(parseSimpleRecurrence("RRULE:FREQ=MONTHLY;WKST=MO"))
+            .isEqualTo(SimpleRecurrence(RecurrenceFreq.Monthly))
+    }
+
+    @Test
+    fun `interval parses`() {
+        assertThat(parseSimpleRecurrence("FREQ=WEEKLY;INTERVAL=2"))
+            .isEqualTo(SimpleRecurrence(RecurrenceFreq.Weekly, interval = 2))
+    }
+
+    @Test
+    fun `until parses date-only and UTC datetime forms`() {
+        val expected = SimpleRecurrence(
+            RecurrenceFreq.Daily,
+            end = RecurrenceEnd.Until(LocalDate(2026, 8, 1)),
+        )
+        assertThat(parseSimpleRecurrence("FREQ=DAILY;UNTIL=20260801", utc)).isEqualTo(expected)
+        assertThat(parseSimpleRecurrence("FREQ=DAILY;UNTIL=20260801T235959Z", utc))
+            .isEqualTo(expected)
+    }
+
+    @Test
+    fun `until datetime converts from UTC into the given zone before taking the date`() {
+        // 21:59:59Z == 23:59:59 in Berlin (CEST) — still August 1 there.
+        assertThat(parseSimpleRecurrence("FREQ=DAILY;UNTIL=20260801T215959Z", berlin))
+            .isEqualTo(
+                SimpleRecurrence(RecurrenceFreq.Daily, end = RecurrenceEnd.Until(LocalDate(2026, 8, 1))),
+            )
+    }
+
+    @Test
+    fun `count parses`() {
+        assertThat(parseSimpleRecurrence("FREQ=YEARLY;COUNT=5"))
+            .isEqualTo(SimpleRecurrence(RecurrenceFreq.Yearly, end = RecurrenceEnd.Count(5)))
+    }
+
+    @Test
+    fun `weekly byday parses as weekday picks`() {
+        assertThat(parseSimpleRecurrence("FREQ=WEEKLY;BYDAY=MO,FR"))
+            .isEqualTo(
+                SimpleRecurrence(
+                    RecurrenceFreq.Weekly,
+                    byDays = setOf(DayOfWeek.MONDAY, DayOfWeek.FRIDAY),
+                ),
+            )
+    }
+
+    @Test
+    fun `rules beyond the simple shape are rejected`() {
+        // Ordinal BYDAY ("second Thursday") and BYDAY on non-weekly rules.
+        assertThat(parseSimpleRecurrence("FREQ=WEEKLY;BYDAY=MO,2TH")).isNull()
+        assertThat(parseSimpleRecurrence("FREQ=MONTHLY;BYDAY=MO")).isNull()
+        assertThat(parseSimpleRecurrence("FREQ=MONTHLY;BYMONTHDAY=15")).isNull()
+        assertThat(parseSimpleRecurrence("FREQ=HOURLY")).isNull()
+        assertThat(parseSimpleRecurrence("")).isNull()
+        assertThat(parseSimpleRecurrence("FREQ=DAILY;UNTIL=20260801;COUNT=3")).isNull()
+        assertThat(parseSimpleRecurrence("FREQ=DAILY;INTERVAL=0")).isNull()
+        assertThat(parseSimpleRecurrence("FREQ=DAILY;COUNT=abc")).isNull()
+    }
+
+    @Test
+    fun `toRRule renders the minimal form`() {
+        assertThat(SimpleRecurrence(RecurrenceFreq.Weekly).toRRule()).isEqualTo("FREQ=WEEKLY")
+        assertThat(SimpleRecurrence(RecurrenceFreq.Daily, interval = 3).toRRule())
+            .isEqualTo("FREQ=DAILY;INTERVAL=3")
+        assertThat(
+            SimpleRecurrence(RecurrenceFreq.Monthly, end = RecurrenceEnd.Count(12)).toRRule(),
+        ).isEqualTo("FREQ=MONTHLY;COUNT=12")
+    }
+
+    @Test
+    fun `toRRule renders weekdays in ISO order regardless of set order`() {
+        val rule = SimpleRecurrence(
+            RecurrenceFreq.Weekly,
+            byDays = setOf(DayOfWeek.FRIDAY, DayOfWeek.MONDAY, DayOfWeek.WEDNESDAY),
+        ).toRRule()
+        assertThat(rule).isEqualTo("FREQ=WEEKLY;BYDAY=MO,WE,FR")
+    }
+
+    @Test
+    fun `toRRule ignores weekday picks on non-weekly frequencies`() {
+        val rule = SimpleRecurrence(
+            RecurrenceFreq.Monthly,
+            byDays = setOf(DayOfWeek.MONDAY),
+        ).toRRule()
+        assertThat(rule).isEqualTo("FREQ=MONTHLY")
+    }
+
+    @Test
+    fun `toRRule writes until as the end of the chosen day in the given zone`() {
+        val rule = SimpleRecurrence(
+            RecurrenceFreq.Weekly,
+            interval = 2,
+            end = RecurrenceEnd.Until(LocalDate(2026, 8, 1)),
+        )
+        assertThat(rule.toRRule(utc))
+            .isEqualTo("FREQ=WEEKLY;INTERVAL=2;UNTIL=20260801T235959Z")
+        // 23:59:59 Berlin (CEST, +2) == 21:59:59Z.
+        assertThat(rule.toRRule(berlin))
+            .isEqualTo("FREQ=WEEKLY;INTERVAL=2;UNTIL=20260801T215959Z")
+    }
+
+    // 2026-06-19T23:59:00Z — a moment just before a June 20 occurrence.
+    private val cutoffMillis = 1_781_913_540_000L
+
+    @Test
+    fun `truncation replaces count and keeps every other part`() {
+        assertThat(rruleTruncatedAt("FREQ=WEEKLY;INTERVAL=2;BYDAY=MO,FR;COUNT=30", cutoffMillis))
+            .isEqualTo("FREQ=WEEKLY;INTERVAL=2;BYDAY=MO,FR;UNTIL=20260619T235900Z")
+    }
+
+    @Test
+    fun `truncation replaces an existing until`() {
+        assertThat(rruleTruncatedAt("FREQ=DAILY;UNTIL=20301231T235959Z", cutoffMillis))
+            .isEqualTo("FREQ=DAILY;UNTIL=20260619T235900Z")
+    }
+
+    @Test
+    fun `truncation works on rules the simple picker cannot express`() {
+        assertThat(rruleTruncatedAt("RRULE:FREQ=MONTHLY;BYDAY=2TH", cutoffMillis))
+            .isEqualTo("FREQ=MONTHLY;BYDAY=2TH;UNTIL=20260619T235900Z")
+    }
+
+    @Test
+    fun `parse and render round-trip`() {
+        val rules = listOf(
+            "FREQ=DAILY",
+            "FREQ=WEEKLY;INTERVAL=2",
+            "FREQ=WEEKLY;INTERVAL=2;BYDAY=MO,FR;UNTIL=20301231T235959Z",
+            "FREQ=MONTHLY;COUNT=6",
+            "FREQ=YEARLY;UNTIL=20301231T235959Z",
+        )
+        rules.forEach { rule ->
+            assertThat(parseSimpleRecurrence(rule, utc)!!.toRRule(utc)).isEqualTo(rule)
+        }
+        // Round-trips through a non-UTC zone too: 22:59:59Z == 23:59:59 CET.
+        val berlinRule = "FREQ=WEEKLY;BYDAY=MO,FR;UNTIL=20301231T225959Z"
+        assertThat(parseSimpleRecurrence(berlinRule, berlin)!!.toRRule(berlin))
+            .isEqualTo(berlinRule)
+    }
+}

docs/superpowers/plans/2026-06-11-03-write-support.md

@@ -47,7 +47,7 @@ Domain bleibt pure Kotlin.
 |---|---|---|
 | v1.1 | Write-Fundament: `WRITE_CALENDAR`, `canModifyContents`, Delete (Serie + einzelnes Vorkommen) | ausgeliefert (v1.1.0, 2026-06-11) |
 | v1.2 | Create: Event-Formular (Titel, Kalender, ganztägig, Start/Ende, Ort, Beschreibung), FAB, Default-Kalender-Pref | ausgeliefert (v1.2.0, 2026-06-11) |
-| v1.3 | Edit: Formular wiederverwendet, Serien-Edit, Reminder-Edit, einfacher Recurrence-Picker | offen |
+| v1.3 | Edit: Formular wiederverwendet, Serien-Edit, Reminder-Edit, einfacher Recurrence-Picker | implementiert (Release wartet auf On-Device-Review) |
 | v2.0 | Quick-Add, Occurrence-Edit, Konflikt-Dialog, Polish-Pass, Release | offen |
 
 ## v1.1 — Write-Fundament + Delete
@@ -95,11 +95,90 @@ Domain bleibt pure Kotlin.
 - [x] `insertEvent(form): Long` im DataSource; `EventWriteMapper` (JVM-testbar)
       normalisiert all-day auf UTC-Mitternächte mit exklusivem DTEND
 
-## v1.3 — Edit (Skizze)
+## v1.3 — Edit
 
-- Formular lädt `EventDetail`, Dirty-Check, `update` auf Events-Row
-- Reminder hinzufügen/entfernen (`Reminders`-Insert/Delete)
-- Einfacher Recurrence-Picker (FREQ + INTERVAL + UNTIL/COUNT)
+**Domain:**
+- [x] `EventForm.rrule` (roher RRULE-Wert, null = einmalig); komplexe Regeln
+      (ordinales BYDAY wie "2TH", BYMONTHDAY etc.) bleiben verbatim erhalten,
+      solange der Picker sie nicht ersetzt
+- [x] `SimpleRecurrence` (FREQ + INTERVAL + UNTIL/COUNT + wöchentliches
+      BYDAY — Review-Feedback: "jede Woche Mo+Fr" muss gehen) mit
+      `parseSimpleRecurrence`/`toRRule` (Recurrence.kt, JVM-getestet)
+- [x] `EventDetail.toEditForm(begin, end, zone)` — Prefill inkl. all-day-
+      Rückrechnung (exklusives DTEND → letzter abgedeckter Tag)
+- [x] Validierung: `RecurrenceEndsBeforeStart` (UNTIL vor erstem Tag hieße
+      null Vorkommen — Event würde unsichtbar)
+
+**Data layer:**
+- [x] `buildEventUpdateValues(original, updated, seriesDtStart, zone)` —
+      Dirty-Check, nur geänderte Spalten; Zeitfelder als Einheit:
+      einmalig → DTSTART/DTEND (RRULE/DURATION genullt), wiederkehrend →
+      Serien-DTSTART verschiebt sich um das User-Delta, DURATION statt DTEND
+- [x] `CalendarDataSource.updateEvent(eventId, original, updated)` — Events-Row-
+      Update + Reminder-Diff nach Minuten (unberührte Rows behalten ihre Methode)
+- [x] `insertEvent` versteht RRULE (RRULE+DURATION statt DTEND — Provider-Invariante)
+- [x] `CalendarRepository(+Impl).updateEvent` durchgereicht, auf `io`
+- [x] `EventDetailMapper`: Titel bleibt roh (kein "(Ohne Titel)"-Fallback mehr —
+      der Detail-Screen ersetzt selbst lokalisiert, das Formular braucht den Rohwert)
+
+**UI:**
+- [x] `EventEditViewModel.openForEdit` (lädt Detail, merkt Original für
+      Dirty-Check; unverändertes Formular speichert als No-Op); Felder mit
+      Werten werden unabhängig vom Settings-Default eingeblendet
+- [x] `EventEditScreen`: `editKey`-Parameter, Kalender im Edit-Modus fixiert,
+      Repeat-Karte + `RecurrencePickerDialog` (Presets per Tap, Custom-Schritt
+      mit Intervall/Einheit + Wochentags-Toggles bei "Wochen" (Wochenstart
+      nach Locale, Start-Wochentag vorausgewählt) + Ende nie/Datum/Anzahl,
+      OptionCard-Stil)
+- [x] Recurrence-Humanizer nach `ui/common/RecurrenceText.kt` (Detail + Formular)
+- [x] `EventDetailScreen`: Edit-Action (nur `canModify`, kontextueller
+      WRITE-Request wie Delete); Save schließt Formular **und** Detail (die
+      getappte Occurrence existiert danach evtl. nicht mehr)
+- [x] **Occurrence-Edit (aus v2.0 vorgezogen, Review-Feedback):** Die
+      Scope-Frage kommt **beim Speichern** (Google-Modell, Review-Feedback):
+      ein dirty wiederkehrender Termin parkt in `SaveUiState.AwaitingScope`,
+      der Dialog bietet "Nur dieser Termin / Dieser und alle folgenden /
+      Ganze Serie"; bei geänderter Wiederholungsregel entfällt "nur dieser"
+      (eine Exception-Row trägt keine eigene Regel). "Nur dieser" schreibt
+      eine Modified-Occurrence-Exception (`CONTENT_EXCEPTION_URI`, alle
+      Formularwerte, leere Optionals als explizite NULLs weil der Provider
+      die Serien-Row klont), Reminder werden gegen die tatsächlichen
+      Provider-Rows abgeglichen. "Dieser und folgende" = Serien-Split:
+      neues Event mit den Formularwerten (insert zuerst — schlägt es fehl,
+      bleibt das Original unberührt), dann Original-RRULE per UNTIL gekappt;
+      ab der ersten Occurrence = normales Serien-Update. Ein mitgenommenes
+      COUNT zählt in der neuen Serie neu (kein Rest-COUNT-Rechnen wie AOSP)
+- [x] **Delete dreistufig (Review-Feedback):** "Nur dieser Termin" /
+      "Dieser und alle folgenden" (RRULE-Truncation via `rruleTruncatedAt`)
+      / "Alle Termine der Serie"; ab der ersten Occurrence = ganze Serie
+      löschen
+- [x] **Split-Duplikat-Bugfix (On-Device-Review):** Nach dem Serien-Split
+      blieb die getappte Occurrence doppelt sichtbar. Root cause (per
+      adb-Probe verifiziert): der Provider regeneriert die Instances eines
+      Events nur aus den **Values des Updates selbst** — ein RRULE-only-
+      Update lässt die alten Instances stehen, und ein Teilset (nur DTSTART)
+      erzeugt kaputte Nulllängen-Instanzen. Truncation-Updates schicken
+      deshalb das komplette Zeit-Set (DTSTART/DURATION/RRULE/ALL_DAY/
+      EVENT_TIMEZONE) zusammen (`truncateSeries`), wie AOSPs
+      EditEventHelper. Zusätzlich (Robustheit, Google-Modell): Cutoff =
+      Ende des Vortags in der Event-Zeitzone (`previousLocalDayEndUtcMillis`)
+      statt Occurrence−1s, und der Recurrence-Picker rendert UNTIL als
+      lokales Tagesende in UTC (`toRRule(zone)`) statt pauschal `T235959Z`
+      (sonst kann bei UTC+x ein Extra-Tag hineinrutschen)
+- [x] `CalendarHost`: Edit-Overlay mit Held-Key-Pattern
+- [x] `EventFormField.Recurrence` (Formular, "Mehr Felder", Settings-Default)
+- [x] Strings DE+EN
+
+**Tests:**
+- [x] `RecurrenceTest` (Parse/Render/Roundtrip, Ablehnung komplexer Regeln)
+- [x] `EventFormTest`: Prefill (timed/all-day), `populatedFields`, UNTIL-Validierung
+- [x] `EventWriteMapperTest`: Duration-Format, Dirty-Check-Pfade (Text-only,
+      Zeit einmalig/wiederkehrend, Recurrence an/aus, Reminder-only)
+- [x] `CalendarRepositoryImplTest` + `FakeCalendarDataSource`: update-Pfade
+- [x] `EventDetailMapperTest`: roher Titel
+
+Bewusst nicht in v1.3 (→ v2.0): Konflikt-Dialog, Kalender-Wechsel beim
+Bearbeiten (Sync-Adapter-Minenfeld, sperren auch alle Stock-Apps).
 
 ## v2.0 — Abschluss (Skizze)