feat(reminders): configurable all-day reminder fire time

All-day events live at UTC midnight, so a raw "1 day before" reminder
fires at an off hour (02:00 local in CEST) rather than the morning. Add a
global "all-day reminder time" setting (default 09:00) and encode it into
the provider MINUTES offset so the reminder lands at the chosen wall-clock
time the day before instead.

- AllDayReminderEncoding: pure to/from provider-minutes helpers, keeping
  the form/UI/diff in whole-day "semantic" minutes and converting only at
  the Reminders read/write boundary (insertEvent, reconcileReminders,
  EventDetailMapper). Covers DST, negative offsets, and pre-existing rows.
- SettingsPrefs.allDayReminderTimeMinutes (default 540) threaded from the
  repository into the data-source write paths.
- Settings: a time-picker row, plus a shared TimePickerAlert lifted from
  the event editor.
- Fix the time picker's 12/24-hour detection: honour an explicit system
  override, else fall back to the device locale rather than the app's
  per-app language, so it matches the rest of the device.

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

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

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

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

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

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

@@ -66,20 +66,36 @@ internal class FakeCalendarDataSource : CalendarDataSource {
         deletedCalendarIds += id
     }
 
-    override fun insertEvent(form: EventForm): Long {
+    /** All-day reminder fire-time minute-of-day passed into the last write. */
+    val allDayReminderTimes = mutableListOf<Int>()
+
+    override fun insertEvent(form: EventForm, allDayReminderTimeMinutes: Int): Long {
         writeError?.let { throw it }
         insertedForms += form
+        allDayReminderTimes += allDayReminderTimeMinutes
         return nextInsertId
     }
 
-    override fun updateEvent(eventId: Long, original: EventForm, updated: EventForm) {
+    override fun updateEvent(
+        eventId: Long,
+        original: EventForm,
+        updated: EventForm,
+        allDayReminderTimeMinutes: Int,
+    ) {
         writeError?.let { throw it }
         updatedEvents += Triple(eventId, original, updated)
+        allDayReminderTimes += allDayReminderTimeMinutes
     }
 
-    override fun updateOccurrence(eventId: Long, beginMillis: Long, form: EventForm): Long {
+    override fun updateOccurrence(
+        eventId: Long,
+        beginMillis: Long,
+        form: EventForm,
+        allDayReminderTimeMinutes: Int,
+    ): Long {
         writeError?.let { throw it }
         updatedOccurrences += Triple(eventId, beginMillis, form)
+        allDayReminderTimes += allDayReminderTimeMinutes
         return nextInsertId
     }
 
@@ -88,9 +104,11 @@ internal class FakeCalendarDataSource : CalendarDataSource {
         beginMillis: Long,
         original: EventForm,
         updated: EventForm,
+        allDayReminderTimeMinutes: Int,
     ): Long {
         writeError?.let { throw it }
         updatedFromOccurrences += Triple(eventId, beginMillis, updated)
+        allDayReminderTimes += allDayReminderTimeMinutes
         return nextInsertId
     }
 

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

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