fix(core-time): render all-day values in UTC, not the device zone

All-day items are date-only in iCalendar and are stored as UTC midnight of
their calendar date — the convention the tasks and calendar providers read
back (OpenTasks resolves them through DateTime.toAllDay(), which discards the
time and resolves the remaining date against UTC).

formatDate/formatDateTime/formatDateTimeCompact resolved every instant against
ZoneId.systemDefault(), so an all-day value rendered as the *previous* day for
anyone west of UTC: a task stored as 2026-07-20T00:00Z showed as 19 Jul in New
York. East of UTC it happened to land on the right day, which is why this went
unnoticed.

formatDate now takes an allDay flag (defaulting to false, so existing call
sites are unaffected) and all-day values resolve against UTC.

Callers must pass allDay at the call site — agendula and calendula both have
sites that need updating.

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

components/build.gradle.kts

@@ -39,8 +39,6 @@ dependencies {
     // core-locale backs the language-picker recipe (AppLanguage).
     implementation(project(":core-locale"))
 
-    implementation(libs.androidx.core.ktx)
-
     implementation(platform(libs.androidx.compose.bom))
     implementation(libs.androidx.ui)
     implementation(libs.androidx.foundation)

components/src/main/kotlin/de/jeanlucmakiola/floret/components/GroupedList.kt

@@ -37,16 +37,6 @@ fun positionOf(index: Int, count: Int): Position = when {
     else -> Position.Middle
 }
 
-/**
- * The inset a grouped list keeps from the screen edge.
- *
- * Exported because it is a *shared* line, not a private detail of [GroupedRow]:
- * everything that sits outside the cards but belongs to them — section headers,
- * hints, picker descriptions — has to start on the same edge, or the page reads
- * as two ragged columns. Take this value rather than writing 16.dp again.
- */
-val GroupedListInset = 16.dp
-
 /** Corner radii for a grouped segment: full at the group's outer edges, small between. */
 fun groupedShape(position: Position, full: Dp, small: Dp): Shape = when (position) {
     Position.Alone -> RoundedCornerShape(full)
@@ -150,7 +140,7 @@ fun GroupedRow(
     }
     GroupedSurface(
         position = position,
-        modifier = modifier.padding(horizontal = GroupedListInset),
+        modifier = modifier.padding(horizontal = 16.dp),
         onClick = onClick,
         color = containerColor,
         gapBelow = gapBelow,

components/src/main/kotlin/de/jeanlucmakiola/floret/components/OptionPicker.kt

@@ -13,8 +13,6 @@ import androidx.compose.ui.platform.LocalView
 import androidx.compose.ui.window.Dialog
 import androidx.compose.ui.window.DialogProperties
 import androidx.compose.ui.window.DialogWindowProvider
-import androidx.core.view.WindowCompat
-import de.jeanlucmakiola.floret.identity.LocalFloretDarkTheme
 
 /**
  * Full-screen scaffold for selection pickers: a full-bleed [Dialog] that reuses
@@ -26,20 +24,6 @@ import de.jeanlucmakiola.floret.identity.LocalFloretDarkTheme
  * [scrollable] forwards to [CollapsingScaffold]: leave it on unless [content]
  * scrolls itself, which a picker only needs for an option list long enough to
  * warrant a lazy container.
- *
- * **Picker richness.** Three shapes, in ascending order — take the cheapest one
- * that makes the choice obvious:
- * 1. plain option rows, when the label *is* the meaning ("English", "Dark");
- * 2. rows plus a per-option summary of the concrete effect, when the meaning is
- *    a date, a time or a number the label only names ("Next 7 days" →
- *    "30 Jul – 5 Aug"). [OptionPicker]'s `summary` covers this;
- * 3. a live preview above the rows, when the effect is *visual* and no words
- *    carry it (month grid style, dimmed past events, week start).
- *
- * A picker of the third kind **must not close when an option is tapped** — it
- * applies immediately and stays open, because closing would hide the very thing
- * the screen exists to show. The user leaves via back. The first two kinds close
- * on tap as usual.
  */
 @Composable
 fun FullScreenPicker(
@@ -57,28 +41,14 @@ fun FullScreenPicker(
             decorFitsSystemWindows = false,
         ),
     ) {
-        // A Compose Dialog owns a separate android.view.Window whose bar-icon
+        // The dialog window pans by default when the keyboard opens, which —
-        // appearance is seeded from the XML theme, not from the activity window's
-        // runtime edge-to-edge state — so with decorFitsSystemWindows = false it
-        // draws edge-to-edge under bars whose icons don't match the active theme
-        // (dark icons on a dark picker). Drive the appearance from the runtime
-        // [LocalFloretDarkTheme] so it tracks the in-app light/dark choice even
-        // when that diverges from the system night qualifier.
-        //
-        // Same window also pans by default when the keyboard opens, which —
         // combined with the content's own imePadding — leaves a fixed black gap
         // above the keyboard. Switch it to ADJUST_NOTHING so the window stays
         // full-screen and imePadding alone lifts the focused field.
         val view = LocalView.current
-        val darkTheme = LocalFloretDarkTheme.current
         SideEffect {
-            (view.parent as? DialogWindowProvider)?.window?.let { window ->
+            (view.parent as? DialogWindowProvider)?.window
-                window.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_NOTHING)
+                ?.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_NOTHING)
-                WindowCompat.getInsetsController(window, view).apply {
-                    isAppearanceLightStatusBars = !darkTheme
-                    isAppearanceLightNavigationBars = !darkTheme
-                }
-            }
         }
         CollapsingScaffold(
             title = title,
@@ -96,15 +66,6 @@ fun FullScreenPicker(
  * General single-select picker, full-screen: each option is a connected grouped
  * row and the current one carries a check. The drop-in for the family's option
  * dialogs (theme, default list, reminder offset, …).
- *
- * [summary] adds a second line per option — reserve it for the option's
- * *concrete effect*, the thing its label names but doesn't spell out: the dates
- * a range resolves to, the time a format renders as, what "follow the system"
- * currently means. Returning null leaves that row single-line, so one option
- * (typically the automatic one) can carry a note the others don't need. It is
- * the cheap middle rung of the richness ladder described on [FullScreenPicker]:
- * every option shows its effect at once and stays comparable, without the cost
- * of a live preview.
  */
 @Composable
 fun <T> OptionPicker(
@@ -114,7 +75,6 @@ fun <T> OptionPicker(
     label: @Composable (T) -> String,
     onSelect: (T) -> Unit,
     onDismiss: () -> Unit,
-    summary: (@Composable (T) -> String?)? = null,
     leading: (@Composable (T) -> Unit)? = null,
     header: (@Composable ColumnScope.() -> Unit)? = null,
     predictiveBack: Boolean = false,
@@ -125,7 +85,6 @@ fun <T> OptionPicker(
             val isSelected = option == selected
             GroupedRow(
                 title = label(option),
-                summary = summary?.invoke(option),
                 position = positionOf(index, options.size),
                 selected = isSelected,
                 leading = leading?.let { { it(option) } },

components/src/main/kotlin/de/jeanlucmakiola/floret/components/SettingsRecipes.kt

@@ -13,10 +13,12 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.FilledTonalButton
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
@@ -39,12 +41,6 @@ data class AboutLink(val icon: ImageVector, val label: String, val url: String)
  * outlined buttons (e.g. source, licence) and an optional full-width
  * [highlightLink] tonal button (e.g. donate). Each link opens its URL in the
  * browser. The app supplies its own logo, strings and links.
- *
- * [position] lets the card join a grouped list instead of standing alone: with
- * [Position.Top] it takes the group's top corners and the 2dp gap below, so a
- * [GroupedRow] underneath continues the same container. Use that when the card's
- * call to action reads better as a row of its own than as a button inside the
- * card — the two then form one block rather than a card with a lid on it.
  */
 @Composable
 fun AboutCard(
@@ -53,16 +49,15 @@ fun AboutCard(
     author: String,
     primaryLinks: List<AboutLink>,
     highlightLink: AboutLink? = null,
-    position: Position = Position.Alone,
 ) {
     val context = LocalContext.current
     val open = { url: String ->
         runCatching { context.startActivity(Intent(Intent.ACTION_VIEW, Uri.parse(url))) }
         Unit
     }
-    GroupedSurface(
+    Surface(
-        position = position,
         color = MaterialTheme.colorScheme.surfaceContainerHigh,
+        shape = RoundedCornerShape(24.dp),
         modifier = Modifier.fillMaxWidth(),
     ) {
         Column(Modifier.fillMaxWidth().padding(16.dp)) {

core-time/src/main/kotlin/de/jeanlucmakiola/floret/time/DateTimeFormat.kt

@@ -3,6 +3,7 @@ package de.jeanlucmakiola.floret.time
 import java.time.LocalDate
 import java.time.LocalTime
 import java.time.ZoneId
+import java.time.ZoneOffset
 import java.time.chrono.IsoChronology
 import java.time.format.DateTimeFormatter
 import java.time.format.DateTimeFormatterBuilder
@@ -22,15 +23,28 @@ private fun Instant.atSystemZone() =
     java.time.Instant.ofEpochMilli(toEpochMilliseconds())
         .atZone(ZoneId.systemDefault())
 
+/**
+ * The zone an instant should be read in to recover the date it denotes.
+ *
+ * All-day items are date-only in iCalendar and are stored as **UTC midnight** of
+ * their calendar date (the convention the tasks/calendar providers read back).
+ * Rendering one in the device zone shows the previous day for anyone west of
+ * UTC — so all-day values resolve against UTC, timed values against the device.
+ */
+private fun Instant.atDisplayZone(allDay: Boolean) =
+    if (allDay) java.time.Instant.ofEpochMilli(toEpochMilliseconds()).atZone(ZoneOffset.UTC)
+    else atSystemZone()
+
 /** Medium localized date, e.g. "18 Jun 2026". */
-fun Instant.formatDate(): String = atSystemZone().format(dateFormatter)
+fun Instant.formatDate(allDay: Boolean = false): String =
+    atDisplayZone(allDay).format(dateFormatter)
 
 /** Short localized time, e.g. "14:30". */
 fun Instant.formatTime(): String = atSystemZone().format(timeFormatter)
 
 /** Date alone for all-day items, otherwise date + time. */
 fun Instant.formatDateTime(allDay: Boolean): String =
-    if (allDay) formatDate() else "${formatDate()} · ${formatTime()}"
+    if (allDay) formatDate(allDay = true) else "${formatDate()} · ${formatTime()}"
 
 // The locale's medium date pattern with the year token stripped, e.g. "20 Jun" /
 // "Jun 20" — derived from the pattern so day/month order still follows the locale.
@@ -49,10 +63,10 @@ private val dateNoYearFormatter: DateTimeFormatter = run {
  * items, or a midnight time). Examples: "20 Jun", "20 Jun · 14:30", "20 Jun 2027".
  */
 fun Instant.formatDateTimeCompact(allDay: Boolean): String {
-    val zdt = atSystemZone()
+    val zdt = atDisplayZone(allDay)
     val datePart =
         if (zdt.year == LocalDate.now(ZoneId.systemDefault()).year) zdt.format(dateNoYearFormatter)
-        else formatDate()
+        else formatDate(allDay)
     return if (allDay || zdt.toLocalTime() == LocalTime.MIDNIGHT) datePart
     else "$datePart · ${formatTime()}"
 }

core-time/src/test/kotlin/de/jeanlucmakiola/floret/time/DateTimeFormatTest.kt

@@ -0,0 +1,76 @@
+package de.jeanlucmakiola.floret.time
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.Test
+import java.time.LocalDate
+import java.time.ZoneOffset
+import java.time.format.DateTimeFormatter
+import java.time.format.FormatStyle
+import java.util.TimeZone
+import kotlin.time.Instant
+
+class DateTimeFormatTest {
+
+    private val originalZone: TimeZone = TimeZone.getDefault()
+
+    @AfterEach
+    fun restoreZone() = TimeZone.setDefault(originalZone)
+
+    private val july20: LocalDate = LocalDate.of(2026, 7, 20)
+
+    /** The all-day storage form: UTC midnight of the calendar date. */
+    private val allDayJuly20: Instant = Instant.fromEpochMilliseconds(
+        july20.atStartOfDay(ZoneOffset.UTC).toInstant().toEpochMilli(),
+    )
+
+    /** What the locale renders for a given date — so the test doesn't pin a format. */
+    private fun medium(date: LocalDate): String =
+        date.format(DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM))
+
+    @Test
+    fun `an all-day date reads the same whatever the device zone`() {
+        TimeZone.setDefault(TimeZone.getTimeZone("America/New_York")) // UTC-4 in July
+        assertThat(allDayJuly20.formatDate(allDay = true)).isEqualTo(medium(july20))
+
+        TimeZone.setDefault(TimeZone.getTimeZone("Europe/Berlin")) // UTC+2 in July
+        assertThat(allDayJuly20.formatDate(allDay = true)).isEqualTo(medium(july20))
+
+        TimeZone.setDefault(TimeZone.getTimeZone("Pacific/Auckland")) // UTC+12
+        assertThat(allDayJuly20.formatDate(allDay = true)).isEqualTo(medium(july20))
+    }
+
+    @Test
+    fun `reading an all-day value as timed slips a day west of UTC`() {
+        // Guards the regression directly: this is what the all-day flag prevents.
+        TimeZone.setDefault(TimeZone.getTimeZone("America/New_York"))
+        assertThat(allDayJuly20.formatDate()).isEqualTo(medium(july20.minusDays(1)))
+        assertThat(allDayJuly20.formatDate(allDay = true)).isEqualTo(medium(july20))
+    }
+
+    @Test
+    fun `timed values still render in the device zone`() {
+        // 2026-07-20T23:30Z — the next day already, in Auckland.
+        val lateUtc = Instant.fromEpochMilliseconds(
+            july20.atTime(23, 30).atZone(ZoneOffset.UTC).toInstant().toEpochMilli(),
+        )
+        TimeZone.setDefault(TimeZone.getTimeZone("Pacific/Auckland"))
+        assertThat(lateUtc.formatDate()).isEqualTo(medium(july20.plusDays(1)))
+    }
+
+    @Test
+    fun `formatDateTime drops the time for all-day and keeps it otherwise`() {
+        TimeZone.setDefault(TimeZone.getTimeZone("Europe/Berlin"))
+        assertThat(allDayJuly20.formatDateTime(allDay = true)).isEqualTo(medium(july20))
+        assertThat(allDayJuly20.formatDateTime(allDay = false)).contains("·")
+    }
+
+    @Test
+    fun `compact form is zone-correct for all-day too`() {
+        TimeZone.setDefault(TimeZone.getTimeZone("America/New_York"))
+        val compact = allDayJuly20.formatDateTimeCompact(allDay = true)
+        // No time part, and the day must not have slipped to the 19th.
+        assertThat(compact).doesNotContain("·")
+        assertThat(compact).contains("20")
+    }
+}

identity/src/main/kotlin/de/jeanlucmakiola/floret/identity/Theme.kt

@@ -10,19 +10,8 @@ import androidx.compose.material3.Typography
 import androidx.compose.material3.dynamicDarkColorScheme
 import androidx.compose.material3.dynamicLightColorScheme
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.CompositionLocalProvider
-import androidx.compose.runtime.staticCompositionLocalOf
 import androidx.compose.ui.platform.LocalContext
 
-/**
- * The resolved light/dark decision the current [FloretExpressiveTheme] is running
- * with, carried down the tree so components can align window chrome (e.g. status-
- * and navigation-bar icon appearance) with the *runtime* theme rather than the
- * system night resource qualifier — the two diverge whenever an app overrides
- * light/dark from settings. Defaults to `false` (light) outside a Floret theme.
- */
-val LocalFloretDarkTheme = staticCompositionLocalOf { false }
-
 /**
  * The family's Material 3 Expressive theme factory. Honours system light/dark
  * and Material You dynamic colour (API 31+), falling back to the app-supplied
@@ -54,7 +43,6 @@ fun FloretExpressiveTheme(
         else -> lightScheme
     }
 
-    CompositionLocalProvider(LocalFloretDarkTheme provides darkTheme) {
     MaterialExpressiveTheme(
         colorScheme = colorScheme,
         typography = typography,
@@ -62,4 +50,3 @@ fun FloretExpressiveTheme(
         content = content,
     )
 }
-}