diff --git a/lib/app.dart b/lib/app.dart
index 570cb41c7..5a3eb58a2 100644
--- a/lib/app.dart
+++ b/lib/app.dart
@@ -10,6 +10,7 @@ import 'l10n/app_localizations.dart';
 import 'notify/notification_service.dart';
 import 'notify/tap_router.dart';
 import 'state/app_state.dart';
+import 'state/clock_format.dart';
 import 'state/locale_controller.dart';
 import 'state/prefs.dart';
 import 'telemetry/telemetry_service.dart';
@@ -122,6 +123,8 @@ class _OpenStrapAppState extends State<OpenStrapApp> with WidgetsBindingObserver
   Widget build(BuildContext context) {
     final theme = context.watch<ThemeController>();
     final locale = context.watch<LocaleController>();
+    final twelveHour = !context.watch<ClockFormatController>().resolve24h(
+        MediaQuery.alwaysUse24HourFormatOf(context));
     return MaterialApp(
       title: 'OpenStrap',
       debugShowCheckedModeBanner: false,
@@ -130,7 +133,11 @@ class _OpenStrapAppState extends State<OpenStrapApp> with WidgetsBindingObserver
       darkTheme: buildTheme(Brightness.dark),
       themeMode: theme.materialThemeMode,
       locale: locale.locale, // null = follow the OS locale
-      localizationsDelegates: AppLocalizations.localizationsDelegates,
+      // First, so a 12-hour choice reaches the time pickers (see the delegate).
+      localizationsDelegates: [
+        ClockMaterialLocalizationsDelegate(twelveHour: twelveHour),
+        ...AppLocalizations.localizationsDelegates,
+      ],
       supportedLocales: AppLocalizations.supportedLocales,
       // Runs even when `locale:` above has a user override — Flutter still
       // calls this callback, just with [locale.locale] as the sole
@@ -152,14 +159,56 @@ class _OpenStrapAppState extends State<OpenStrapApp> with WidgetsBindingObserver
         }
         return const Locale('en');
       },
-      builder: (context, child) =>
-          ThemeSwitchOverlay(key: themeSwitchKey, child: child!),
+      builder: (context, child) => _ClockScope(
+          child: ThemeSwitchOverlay(key: themeSwitchKey, child: child!)),
       navigatorObservers: [TelemetryNavigatorObserver()],
       home: const _Gate(),
     );
   }
 }
 
+/// Applies the 12/24-hour choice: overrides MediaQuery for time pickers (a
+/// 12-hour dial in de/es/fr also needs [ClockMaterialLocalizationsDelegate]),
+/// hands the locale's AM/PM text to `formatClock*`, and rebuilds everything
+/// below once when either flips, since those context-free helpers can't
+/// register a dependency.
+class _ClockScope extends StatefulWidget {
+  const _ClockScope({required this.child});
+  final Widget child;
+
+  @override
+  State<_ClockScope> createState() => _ClockScopeState();
+}
+
+class _ClockScopeState extends State<_ClockScope> {
+  (bool, Locale)? _last;
+
+  @override
+  Widget build(BuildContext context) {
+    final use24 = context
+        .watch<ClockFormatController>()
+        .resolve24h(MediaQuery.alwaysUse24HourFormatOf(context));
+    bindClockLocalizations(MaterialLocalizations.of(context));
+    final now = (use24, Localizations.localeOf(context));
+    if (_last != null && _last != now) {
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        if (!mounted) return;
+        void mark(Element e) {
+          e.markNeedsBuild();
+          e.visitChildren(mark);
+        }
+
+        (context as Element).visitChildren(mark);
+      });
+    }
+    _last = now;
+    return MediaQuery(
+      data: MediaQuery.of(context).copyWith(alwaysUse24HourFormat: use24),
+      child: widget.child,
+    );
+  }
+}
+
 // ══════════════════ THE ONBOARDING GATE ══════════════════
 
 /// The gate, as a pure function of its inputs. Onboarding order bugs are
diff --git a/lib/coach/coach_actions.dart b/lib/coach/coach_actions.dart
index efe7e766e..0526e7eeb 100644
--- a/lib/coach/coach_actions.dart
+++ b/lib/coach/coach_actions.dart
@@ -443,7 +443,7 @@ class CoachActions {
       ],
       'today': [
         for (final s in slots)
-          {'name': s.def.label, 'time': s.timeLabel, 'state': s.state.name},
+          {'name': s.def.label, 'time': s.timeMachine, 'state': s.state.name},
       ],
     });
   }
diff --git a/lib/data/journal_fields.dart b/lib/data/journal_fields.dart
index f1f3021a6..c9db701cf 100644
--- a/lib/data/journal_fields.dart
+++ b/lib/data/journal_fields.dart
@@ -15,6 +15,8 @@ import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';
 
+import '../state/clock_format.dart';
+
 /// What a field measures, which decides how it is entered and read back.
 enum JournalFieldKind {
   /// A subjective 1–5 self-report (mood, sleep quality). Ordinal: the gap
@@ -305,11 +307,6 @@ String customJournalFieldKey(String label) {
   return 'custom_$slug';
 }
 
-/// Local minutes past midnight → "7:05 AM".
-String formatMinuteOfDay(int minuteOfDay) {
-  final m = minuteOfDay % (24 * 60);
-  final h24 = m ~/ 60;
-  final mm = (m % 60).toString().padLeft(2, '0');
-  final h = h24 % 12 == 0 ? 12 : h24 % 12;
-  return '$h:$mm ${h24 < 12 ? 'AM' : 'PM'}';
-}
+/// Local minutes past midnight → "7:05 AM" or "07:05", per the user's clock
+/// format ([formatClockMinute]).
+String formatMinuteOfDay(int minuteOfDay) => formatClockMinute(minuteOfDay);
diff --git a/lib/data/med_store.dart b/lib/data/med_store.dart
index b94cf3591..673032c37 100644
--- a/lib/data/med_store.dart
+++ b/lib/data/med_store.dart
@@ -18,6 +18,7 @@ import 'dart:convert';
 
 import 'package:sqflite/sqflite.dart';
 
+import '../state/clock_format.dart' show formatClockMinute;
 import 'day_label.dart';
 
 // ══════════════════ SCHEMA ══════════════════
@@ -165,10 +166,14 @@ class MedSlot {
   final int slotMin;
   final DoseState state;
 
-  String get timeLabel {
-    final h = (slotMin ~/ 60).toString().padLeft(2, '0');
-    final m = (slotMin % 60).toString().padLeft(2, '0');
-    return '$h:$m';
+  /// Display only, per the user's clock format — never a storage key.
+  String get timeLabel => formatClockMinute(slotMin);
+
+  /// `HH:mm` for payloads and the coach, whatever the clock format.
+  String get timeMachine {
+    final h = slotMin ~/ 60;
+    final m = slotMin % 60;
+    return '${h.toString().padLeft(2, '0')}:${m.toString().padLeft(2, '0')}';
   }
 
   /// A slot that has passed and was neither taken nor deliberately skipped.
diff --git a/lib/l10n/app_de.arb b/lib/l10n/app_de.arb
index e1c2e6125..8031361c4 100644
--- a/lib/l10n/app_de.arb
+++ b/lib/l10n/app_de.arb
@@ -2147,6 +2147,10 @@
   "settingsGroupPreferences": "Einstellungen",
   "settingsUnitsRowTitle": "Einheiten",
   "settingsAppearanceRowTitle": "Erscheinungsbild",
+  "settingsClockFormatRowTitle": "Uhrzeitformat",
+  "settingsClockFormatSystem": "System",
+  "settingsClockFormat24h": "24 Stunden",
+  "settingsClockFormat12h": "12 Stunden",
   "settingsCycleTrackingRowTitle": "Zyklus-Tracking",
   "settingsCycleTrackingRowSub": "Fügt den Tab Zyklus zu Wellness hinzu. Aus blendet ihn aus und behält alles bereits Erfasste",
   "settingsGroupYourData": "Deine Daten",
diff --git a/lib/l10n/app_en.arb b/lib/l10n/app_en.arb
index ae97e419e..ed145a1fe 100644
--- a/lib/l10n/app_en.arb
+++ b/lib/l10n/app_en.arb
@@ -11253,6 +11253,22 @@
   "@settingsAppearanceRowTitle": {
     "description": "Settings row title cycling the app theme"
   },
+  "settingsClockFormatRowTitle": "Time format",
+  "@settingsClockFormatRowTitle": {
+    "description": "Settings row title cycling the 12/24-hour clock format"
+  },
+  "settingsClockFormatSystem": "System",
+  "@settingsClockFormatSystem": {
+    "description": "Clock format value: follow the operating system setting"
+  },
+  "settingsClockFormat24h": "24-hour",
+  "@settingsClockFormat24h": {
+    "description": "Clock format value: 24-hour clock (e.g. 19:30)"
+  },
+  "settingsClockFormat12h": "12-hour",
+  "@settingsClockFormat12h": {
+    "description": "Clock format value: 12-hour clock with AM/PM (e.g. 7:30 PM)"
+  },
   "settingsCycleTrackingRowTitle": "Cycle tracking",
   "@settingsCycleTrackingRowTitle": {
     "description": "Settings row title toggling cycle tracking"
diff --git a/lib/l10n/app_es.arb b/lib/l10n/app_es.arb
index 8612c4529..c4fa8e8f6 100644
--- a/lib/l10n/app_es.arb
+++ b/lib/l10n/app_es.arb
@@ -2159,6 +2159,10 @@
   "settingsGroupPreferences": "Preferencias",
   "settingsUnitsRowTitle": "Unidades",
   "settingsAppearanceRowTitle": "Apariencia",
+  "settingsClockFormatRowTitle": "Formato de hora",
+  "settingsClockFormatSystem": "Sistema",
+  "settingsClockFormat24h": "24 horas",
+  "settingsClockFormat12h": "12 horas",
   "settingsCycleTrackingRowTitle": "Seguimiento del ciclo",
   "settingsCycleTrackingRowSub": "Agrega la pestaña Ciclo a Bienestar. Desactivado la oculta y conserva todo lo ya registrado",
   "settingsGroupYourData": "Tus datos",
diff --git a/lib/l10n/app_fr.arb b/lib/l10n/app_fr.arb
index c760566d0..e85fbd106 100644
--- a/lib/l10n/app_fr.arb
+++ b/lib/l10n/app_fr.arb
@@ -2147,6 +2147,10 @@
   "settingsGroupPreferences": "Préférences",
   "settingsUnitsRowTitle": "Unités",
   "settingsAppearanceRowTitle": "Apparence",
+  "settingsClockFormatRowTitle": "Format de l’heure",
+  "settingsClockFormatSystem": "Système",
+  "settingsClockFormat24h": "24 heures",
+  "settingsClockFormat12h": "12 heures",
   "settingsCycleTrackingRowTitle": "Suivi du cycle",
   "settingsCycleTrackingRowSub": "Ajoute l’onglet Cycle à Bien-être. Désactivé le masque et conserve tout ce qui est déjà enregistré",
   "settingsGroupYourData": "Vos données",
diff --git a/lib/l10n/app_hi.arb b/lib/l10n/app_hi.arb
index a41b9a60b..5baa5637c 100644
--- a/lib/l10n/app_hi.arb
+++ b/lib/l10n/app_hi.arb
@@ -2147,6 +2147,10 @@
   "settingsGroupPreferences": "प्राथमिकताएं",
   "settingsUnitsRowTitle": "इकाइयां",
   "settingsAppearanceRowTitle": "रूप",
+  "settingsClockFormatRowTitle": "समय प्रारूप",
+  "settingsClockFormatSystem": "सिस्टम",
+  "settingsClockFormat24h": "24 घंटे",
+  "settingsClockFormat12h": "12 घंटे",
   "settingsCycleTrackingRowTitle": "चक्र ट्रैकिंग",
   "settingsCycleTrackingRowSub": "वेलनेस में साइकिल टैब जोड़ता है। बंद करने पर यह छिप जाता है और पहले से लॉग किया गया सब कुछ बना रहता है",
   "settingsGroupYourData": "आपका डेटा",
diff --git a/lib/l10n/app_zh.arb b/lib/l10n/app_zh.arb
index f31d7ab86..46847d602 100644
--- a/lib/l10n/app_zh.arb
+++ b/lib/l10n/app_zh.arb
@@ -2147,6 +2147,10 @@
   "settingsGroupPreferences": "偏好设置",
   "settingsUnitsRowTitle": "单位",
   "settingsAppearanceRowTitle": "外观",
+  "settingsClockFormatRowTitle": "时间格式",
+  "settingsClockFormatSystem": "跟随系统",
+  "settingsClockFormat24h": "24 小时制",
+  "settingsClockFormat12h": "12 小时制",
   "settingsCycleTrackingRowTitle": "周期追踪",
   "settingsCycleTrackingRowSub": "在“健康”中添加“周期”标签页。关闭后会隐藏该标签页，但已记录的内容仍会保留",
   "settingsGroupYourData": "你的数据",
diff --git a/lib/main.dart b/lib/main.dart
index 421ba5b50..7ffdd00f4 100644
--- a/lib/main.dart
+++ b/lib/main.dart
@@ -9,6 +9,7 @@ import 'notify/notification_service.dart';
 import 'coach/coach_config.dart';
 import 'state/app_state.dart';
 import 'state/prefs.dart';
+import 'state/clock_format.dart';
 import 'state/locale_controller.dart';
 import 'state/units_controller.dart';
 import 'sync/headless_boot.dart';
@@ -160,6 +161,16 @@ Future<void> main() async {
     units = UnitsController.seed(UnitSystem.metric);
   }
 
+  // Local 12/24-hour clock preference. Best-effort; defaults to the OS setting.
+  // The timeout lives inside bootstrap() so a late load can't replace the seed.
+  ClockFormatController clockFormat;
+  try {
+    clockFormat = await ClockFormatController.bootstrap(timeout: _kStartupInitTimeout);
+  } catch (e, st) {
+    debugPrint('[main] ClockFormatController.bootstrap failed, using system: $e\n$st');
+    clockFormat = ClockFormatController.seed(ClockFormat.system);
+  }
+
   // Local language override (null = system default).
   LocaleController locale;
   try {
@@ -189,6 +200,7 @@ Future<void> main() async {
         ChangeNotifierProvider(create: (_) => AppState(), lazy: false),
         ChangeNotifierProvider<ThemeController>.value(value: theme),
         ChangeNotifierProvider<UnitsController>.value(value: units),
+        ChangeNotifierProvider<ClockFormatController>.value(value: clockFormat),
         ChangeNotifierProvider<LocaleController>.value(value: locale),
         ChangeNotifierProvider<CoachConfig>.value(value: coachConfig),
       ],
diff --git a/lib/notify/battery_forecast.dart b/lib/notify/battery_forecast.dart
index 0cf5fbdd1..77ee54ed3 100644
--- a/lib/notify/battery_forecast.dart
+++ b/lib/notify/battery_forecast.dart
@@ -25,6 +25,8 @@
 
 import 'dart:math' as math;
 
+import '../state/clock_format.dart' show formatClockOf;
+
 /// One battery observation from `band_battery`.
 class BatterySample {
   const BatterySample({
@@ -355,9 +357,8 @@ class BatteryForecaster {
     final pct = f.currentPct;
     final empty = f.predictedEmptyAt;
     if (rate == null || pct == null || empty == null) return '';
-    final h = empty.hour.toString().padLeft(2, '0');
-    final m = empty.minute.toString().padLeft(2, '0');
-    final head = 'At ${rate.toStringAsFixed(1)}%/h it runs out around $h:$m';
+    final head = 'At ${rate.toStringAsFixed(1)}%/h it runs out around '
+        '${formatClockOf(empty)}';
     if (empty.isBefore(wakeAt)) {
       return '$head — before you wake. Charge it now to keep tonight\'s sleep.';
     }
diff --git a/lib/notify/notification_center.dart b/lib/notify/notification_center.dart
index 210fcd64b..cc96b18f1 100644
--- a/lib/notify/notification_center.dart
+++ b/lib/notify/notification_center.dart
@@ -33,6 +33,7 @@ import '../ai/reminder_plan.dart';
 import '../data/day_label.dart';
 import '../data/journal_fields.dart';
 import '../data/med_store.dart';
+import '../state/clock_format.dart' show formatClockMinute;
 import 'fired_keys.dart';
 import 'notification_event.dart';
 import 'notification_prefs.dart';
@@ -531,12 +532,8 @@ class NotificationCenter {
     return t;
   }
 
-  /// Two-digit HH:MM from minutes-past-midnight (notification bodies).
-  static String _hhmm(int minuteOfDay) {
-    final m = minuteOfDay % 1440;
-    return '${(m ~/ 60).toString().padLeft(2, '0')}:'
-        '${(m % 60).toString().padLeft(2, '0')}';
-  }
+  /// Minutes-past-midnight → the user's clock format (notification bodies).
+  static String _hhmm(int minuteOfDay) => formatClockMinute(minuteOfDay);
 
   // ── the weekly lookback finding ─────────────────────────────────────────
 
diff --git a/lib/state/clock_format.dart b/lib/state/clock_format.dart
new file mode 100644
index 000000000..7e4dabae4
--- /dev/null
+++ b/lib/state/clock_format.dart
@@ -0,0 +1,180 @@
+// Clock format: a local display preference (system / 24-hour / 12-hour),
+// persisted like UnitsController. Display only; stored, exported and coach
+// values stay `HH:mm`. The formatters are context-free and read the last
+// controller built, falling back to the OS setting when there is none.
+
+import 'dart:ui' show PlatformDispatcher;
+
+import 'package:flutter/foundation.dart' show SynchronousFuture;
+import 'package:flutter/material.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
+import 'package:intl/intl.dart' as intl;
+import 'package:shared_preferences/shared_preferences.dart';
+
+enum ClockFormat { system, h24, h12 }
+
+extension ClockFormatLabel on ClockFormat {
+  String get label => switch (this) {
+        ClockFormat.system => 'System',
+        ClockFormat.h24 => '24-hour',
+        ClockFormat.h12 => '12-hour',
+      };
+}
+
+class ClockFormatController extends ChangeNotifier {
+  static const String _kClockFormat = 'clock_format'; // 'system'|'h24'|'h12'
+
+  static ClockFormatController? _active;
+
+  ClockFormat _format;
+  ClockFormatController._(this._format) {
+    _active = this;
+  }
+
+  factory ClockFormatController.seed(ClockFormat f) =>
+      ClockFormatController._(f);
+
+  static Future<ClockFormatController> bootstrap({
+    Duration timeout = const Duration(seconds: 6),
+  }) async {
+    final prefs = await SharedPreferences.getInstance().timeout(timeout);
+    return ClockFormatController._(_parse(prefs.getString(_kClockFormat)));
+  }
+
+  /// An unknown stored value (an older build, a hand-edited pref) is "system".
+  static ClockFormat _parse(String? s) => ClockFormat.values
+      .firstWhere((f) => f.name == s, orElse: () => ClockFormat.system);
+
+  ClockFormat get format => _format;
+
+  /// Whether [format] resolves to 24-hour, given the OS's own answer.
+  bool resolve24h(bool systemUse24h) => switch (_format) {
+        ClockFormat.system => systemUse24h,
+        ClockFormat.h24 => true,
+        ClockFormat.h12 => false,
+      };
+
+  Future<void> setFormat(ClockFormat f) async {
+    if (_format == f) return;
+    _format = f;
+    notifyListeners();
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setString(_kClockFormat, f.name);
+  }
+
+  /// Tapped through in place, like Units and Appearance.
+  Future<void> cycle() => setFormat(
+      ClockFormat.values[(_format.index + 1) % ClockFormat.values.length]);
+
+  /// Tests only: forget the active controller so the next test starts from
+  /// the OS setting again.
+  @visibleForTesting
+  static void debugReset() {
+    _active = null;
+    _localizations = null;
+  }
+}
+
+/// The app locale's AM/PM text and 12-hour order, bound by the app's clock
+/// scope. Null (no app yet, a background isolate) falls back to English.
+MaterialLocalizations? _localizations;
+
+void bindClockLocalizations(MaterialLocalizations? l) => _localizations = l;
+
+/// Whether clock times render 24-hour right now: the user's choice, or the
+/// OS's "use 24-hour format" when the choice is "system" (or no controller
+/// exists in this isolate).
+bool get use24HourClock {
+  final system = _systemUse24h();
+  return ClockFormatController._active?.resolve24h(system) ?? system;
+}
+
+/// The OS setting, via the binding's dispatcher when there is one (the one
+/// MediaQuery reads).
+bool _systemUse24h() {
+  try {
+    return WidgetsBinding.instance.platformDispatcher.alwaysUse24HourFormat;
+  } catch (_) {
+    return PlatformDispatcher.instance.alwaysUse24HourFormat;
+  }
+}
+
+/// Hour + minute → "07:05" or "7:05 AM" (the locale's AM/PM), per
+/// [use24HourClock].
+String formatClock(int hour, int minute) {
+  final mm = minute.toString().padLeft(2, '0');
+  if (use24HourClock) return '${hour.toString().padLeft(2, '0')}:$mm';
+  final h = hour % 12 == 0 ? 12 : hour % 12;
+  final l = _localizations;
+  final period = hour < 12
+      ? (l?.anteMeridiemAbbreviation ?? 'AM')
+      : (l?.postMeridiemAbbreviation ?? 'PM');
+  // A 24-hour-native locale (de, fr, es) has no 12-hour order of its own, so
+  // the period goes after, as in English.
+  return l?.timeOfDayFormat() == TimeOfDayFormat.a_space_h_colon_mm
+      ? '$period $h:$mm'
+      : '$h:$mm $period';
+}
+
+/// The time of day of [d], as [formatClock].
+String formatClockOf(DateTime d) => formatClock(d.hour, d.minute);
+
+/// Local minutes past midnight, as [formatClock]. Wraps past 24 h.
+String formatClockMinute(int minuteOfDay) {
+  final m = minuteOfDay % 1440; // Dart's % is never negative here
+  return formatClock(m ~/ 60, m % 60);
+}
+
+/// The time picker only takes `alwaysUse24HourFormat` as a way to force
+/// 24-hour; `false` leaves a 24-hour-native locale (de, es, fr) on its 24-hour
+/// dial. When the clock resolves to 12-hour this hands those locales the same
+/// translations with a 12-hour order, so pickers match [formatClock].
+class ClockMaterialLocalizationsDelegate
+    extends LocalizationsDelegate<MaterialLocalizations> {
+  const ClockMaterialLocalizationsDelegate({required this.twelveHour});
+  final bool twelveHour;
+
+  // ponytail: only the 24-hour-native languages the app ships; a new one
+  // falls through to the stock delegate (24-hour dial) until listed here.
+  static const _langs = {'de', 'es', 'fr'};
+
+  @override
+  bool isSupported(Locale locale) =>
+      twelveHour && _langs.contains(locale.languageCode);
+
+  @override
+  Future<MaterialLocalizations> load(Locale locale) {
+    // Loads intl's date symbols (cached), which the formats below need.
+    GlobalMaterialLocalizations.delegate.load(locale);
+    final n = locale.languageCode;
+    final make = switch (n) {
+      'de' => _De12.new,
+      'es' => _Es12.new,
+      _ => _Fr12.new,
+    };
+    return SynchronousFuture(make(
+      fullYearFormat: intl.DateFormat.y(n),
+      compactDateFormat: intl.DateFormat.yMd(n),
+      shortDateFormat: intl.DateFormat.yMMMd(n),
+      mediumDateFormat: intl.DateFormat.MMMEd(n),
+      longDateFormat: intl.DateFormat.yMMMMEEEEd(n),
+      yearMonthFormat: intl.DateFormat.yMMMM(n),
+      shortMonthDayFormat: intl.DateFormat.MMMd(n),
+      decimalFormat: intl.NumberFormat.decimalPattern(n),
+      twoDigitZeroPaddedFormat: intl.NumberFormat('00', n),
+    ));
+  }
+
+  @override
+  bool shouldReload(ClockMaterialLocalizationsDelegate old) =>
+      old.twelveHour != twelveHour;
+}
+
+mixin _TwelveHour on GlobalMaterialLocalizations {
+  @override
+  TimeOfDayFormat get timeOfDayFormatRaw => TimeOfDayFormat.h_colon_mm_space_a;
+}
+
+class _De12 = MaterialLocalizationDe with _TwelveHour;
+class _Es12 = MaterialLocalizationEs with _TwelveHour;
+class _Fr12 = MaterialLocalizationFr with _TwelveHour;
diff --git a/lib/ui2/activity/poster.dart b/lib/ui2/activity/poster.dart
index 24ca2e359..b28bab92b 100644
--- a/lib/ui2/activity/poster.dart
+++ b/lib/ui2/activity/poster.dart
@@ -36,6 +36,7 @@ import 'package:flutter/material.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
 
 import '../../l10n/app_localizations.dart';
+import '../../state/clock_format.dart' show formatClockOf;
 import '../../state/units_controller.dart';
 import '../screens/home_screen.dart' show unitsOf;
 import '../theme.dart';
@@ -920,16 +921,13 @@ void drawPin(Canvas canvas, Offset o, Color col) {
   );
 }
 
-/// `20 May 2026 • 7:15 AM`, in the reader's own clock terms.
+/// `May 20, 2026 • 7:15 AM` (or `07:15`), in the reader's own clock terms.
 String posterDate(DateTime t) {
   const m = [
     'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
     'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec',
   ];
-  final h = t.hour % 12 == 0 ? 12 : t.hour % 12;
-  final min = t.minute.toString().padLeft(2, '0');
-  return '${m[t.month - 1]} ${t.day}, ${t.year} • $h:$min '
-      '${t.hour < 12 ? 'AM' : 'PM'}';
+  return '${m[t.month - 1]} ${t.day}, ${t.year} • ${formatClockOf(t)}';
 }
 
 /// Hero, unit, caption — distance when the session has one, time when it does
diff --git a/lib/ui2/activity/summary.dart b/lib/ui2/activity/summary.dart
index d92c8ede5..6743fc6df 100644
--- a/lib/ui2/activity/summary.dart
+++ b/lib/ui2/activity/summary.dart
@@ -30,6 +30,7 @@ import '../../data/db.dart';
 import '../../gps/gpx_export.dart';
 import '../../l10n/app_localizations.dart';
 import '../../state/app_state.dart';
+import '../../state/clock_format.dart' show formatClockOf;
 import '../../state/prefs.dart';
 import '../../state/units_controller.dart';
 import '../charts.dart';
@@ -501,9 +502,7 @@ String _shortDate(DateTime t) {
     'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
     'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec',
   ];
-  final h = t.hour % 12 == 0 ? 12 : t.hour % 12;
-  return '${months[t.month - 1]} ${t.day}, ${t.year} at $h:'
-      '${t.minute.toString().padLeft(2, '0')} ${t.hour < 12 ? 'AM' : 'PM'}';
+  return '${months[t.month - 1]} ${t.day}, ${t.year} at ${formatClockOf(t)}';
 }
 
 // ── THE SUPPORTING STATS ───────────────────────────────────────────────────
diff --git a/lib/ui2/profile/alarm.dart b/lib/ui2/profile/alarm.dart
index 410bb9ac1..0e5405353 100644
--- a/lib/ui2/profile/alarm.dart
+++ b/lib/ui2/profile/alarm.dart
@@ -28,6 +28,7 @@ import 'package:provider/provider.dart';
 import '../../l10n/app_localizations.dart';
 import '../../state/alarm_schedule.dart';
 import '../../state/app_state.dart';
+import '../../state/clock_format.dart' show formatClock;
 import '../screens/home_screen.dart' show weekdayShortName;
 import '../ui2.dart';
 import 'profile.dart' show SetRow, settingsGroup;
@@ -285,8 +286,7 @@ class AlarmScreenView extends StatelessWidget {
 
   static String _hhmm(DateTime d) => _hhmmOf(d.hour, d.minute);
 
-  static String _hhmmOf(int hour, int minute) =>
-      '${hour.toString().padLeft(2, '0')}:${minute.toString().padLeft(2, '0')}';
+  static String _hhmmOf(int hour, int minute) => formatClock(hour, minute);
 
   /// "Tue 07:30" — the weekday plus the time, both from the ARMED instant
   /// (not merely from the schedule row), so this never claims a day the band
diff --git a/lib/ui2/profile/data.dart b/lib/ui2/profile/data.dart
index 69db5fbc0..c077aab6f 100644
--- a/lib/ui2/profile/data.dart
+++ b/lib/ui2/profile/data.dart
@@ -27,6 +27,7 @@ import '../../data/db.dart';
 import '../../import/backup_crypto.dart';
 import '../../l10n/app_localizations.dart';
 import '../../state/app_state.dart';
+import '../../state/clock_format.dart' show formatClockOf;
 import '../activity/share.dart' show shareOrigin;
 import '../onboarding/welcome.dart'
     show
@@ -394,6 +395,5 @@ BackupCadence _nextCadence(BackupCadence c) => BackupCadence
 
 String _stamp(DateTime t) {
   String two(int v) => v.toString().padLeft(2, '0');
-  return '${t.year}-${two(t.month)}-${two(t.day)} '
-      '${two(t.hour)}:${two(t.minute)}';
+  return '${t.year}-${two(t.month)}-${two(t.day)} ${formatClockOf(t)}';
 }
diff --git a/lib/ui2/profile/devices.dart b/lib/ui2/profile/devices.dart
index 008ea5414..64ff39545 100644
--- a/lib/ui2/profile/devices.dart
+++ b/lib/ui2/profile/devices.dart
@@ -116,6 +116,7 @@ import '../../notify/battery_forecast.dart';
 import '../../state/prefs.dart' show Prefs;
 import '../../sync/paired_device.dart' show cleanDeviceLabel;
 import '../../state/app_state.dart';
+import '../../state/clock_format.dart' show formatClockOf;
 import '../pairing/device_picker.dart' show DevicePickerScreen;
 import '../onboarding/profile_setup.dart' show formatDay;
 import '../ui2.dart';
@@ -2825,8 +2826,5 @@ String? _chargeHistory(Map<String, dynamic>? h) {
 ///
 /// It used to render `4/9, 07:12`, which a US reader reads as 9 April. The
 /// month name is the whole point; `formatDay` already writes one.
-String formatDayTime(DateTime d, [AppLocalizations? l]) {
-  final t = '${d.hour.toString().padLeft(2, '0')}:'
-      '${d.minute.toString().padLeft(2, '0')}';
-  return '${formatDay(d, l)}, $t';
-}
+String formatDayTime(DateTime d, [AppLocalizations? l]) =>
+    '${formatDay(d, l)}, ${formatClockOf(d)}';
diff --git a/lib/ui2/profile/settings.dart b/lib/ui2/profile/settings.dart
index 2d24b6d13..cd355e639 100644
--- a/lib/ui2/profile/settings.dart
+++ b/lib/ui2/profile/settings.dart
@@ -29,6 +29,7 @@ import '../../notify/notification_prefs.dart';
 import '../../notify/notification_service.dart';
 import '../../platform/app_icon.dart';
 import '../../state/app_state.dart';
+import '../../state/clock_format.dart';
 import '../../state/prefs.dart';
 import '../../state/units_controller.dart';
 import '../../telemetry/health_uploader.dart';
@@ -148,6 +149,7 @@ class _MoreSettingsState extends State<MoreSettings> {
     final app = c.watch<AppState>();
     final units = c.watch<UnitsController>();
     final theme = c.watch<ThemeController>();
+    final clock = c.watch<ClockFormatController>();
     return MoreSettingsView(
       version: _version,
       devMode: _dev,
@@ -156,6 +158,7 @@ class _MoreSettingsState extends State<MoreSettings> {
       onGallery: () => goto(c, const GalleryScreen()),
       units: units.system.label,
       appearance: theme.choice.label,
+      clockFormat: clock.format,
       cycleTracking: app.cycleTrackingEnabled,
       zoneAlertEnabled: app.zoneAlertEnabled,
       zoneAlertZone: app.zoneAlertTargetZone,
@@ -187,6 +190,11 @@ class _MoreSettingsState extends State<MoreSettings> {
           : UnitSystem.imperial),
       onCycleAppearance: () => theme.setChoice(AppThemeChoice.values[
           (theme.choice.index + 1) % AppThemeChoice.values.length]),
+      // the wind-down body bakes the time in when it's armed, re-arm it now
+      onCycleClockFormat: () async {
+        await clock.cycle();
+        await app.refreshAiReminders();
+      },
       onToggleCycleTracking: () =>
           app.setCycleTrackingEnabled(!app.cycleTrackingEnabled),
       onTogglePhoneSteps: () => app.phoneStepsEnabled
@@ -481,6 +489,9 @@ Future<void> _confirmReset(BuildContext c, AppState app) async {
 
 class MoreSettingsView extends StatelessWidget {
   final String units, appearance;
+
+  /// 12- or 24-hour clock, or whatever the OS says ("System", the default).
+  final ClockFormat clockFormat;
   final bool phoneSteps, telemetry, barcodeLookup, cycleTracking;
 
   /// The live-workout HR-zone-crossing haptic. Off by default; [zoneAlertZone]
@@ -530,6 +541,7 @@ class MoreSettingsView extends StatelessWidget {
       onAutomation,
       onCycleUnits,
       onCycleAppearance,
+      onCycleClockFormat,
       onTogglePhoneSteps,
       onToggleTelemetry,
       onToggleBarcodeLookup,
@@ -545,6 +557,7 @@ class MoreSettingsView extends StatelessWidget {
     super.key,
     this.units = 'Metric',
     this.appearance = 'System',
+    this.clockFormat = ClockFormat.system,
     this.appIcon,
     this.onPickIcon,
     this.phoneSteps = false,
@@ -574,6 +587,7 @@ class MoreSettingsView extends StatelessWidget {
     this.onAutomation,
     this.onCycleUnits,
     this.onCycleAppearance,
+    this.onCycleClockFormat,
     this.onTogglePhoneSteps,
     this.onToggleTelemetry,
     this.onToggleBarcodeLookup,
@@ -666,6 +680,17 @@ class MoreSettingsView extends StatelessWidget {
                   SetRow(LucideIcons.sun, C.yellow,
                       l?.settingsAppearanceRowTitle ?? 'Appearance',
                       value: appearance, onTap: onCycleAppearance),
+                  SetRow(LucideIcons.clock, C.teal,
+                      l?.settingsClockFormatRowTitle ?? 'Time format',
+                      value: switch (clockFormat) {
+                        ClockFormat.system =>
+                          l?.settingsClockFormatSystem ?? clockFormat.label,
+                        ClockFormat.h24 =>
+                          l?.settingsClockFormat24h ?? clockFormat.label,
+                        ClockFormat.h12 =>
+                          l?.settingsClockFormat12h ?? clockFormat.label,
+                      },
+                      onTap: onCycleClockFormat),
                   if (appIcon != null)
                     _IconRow(chosen: appIcon!, onPick: onPickIcon),
                   // Opt-in, and it says what it does rather than what it is
@@ -1265,11 +1290,7 @@ class NotificationSettingsView extends StatelessWidget {
     return batteryChoices[(i + 1) % batteryChoices.length];
   }
 
-  static String _hhmm(int minuteOfDay) {
-    final m = minuteOfDay % 1440;
-    return '${(m ~/ 60).toString().padLeft(2, '0')}:'
-        '${(m % 60).toString().padLeft(2, '0')}';
-  }
+  static String _hhmm(int minuteOfDay) => formatClockMinute(minuteOfDay);
 
   static Future<int?> _pickMinute(BuildContext c, int current) async {
     final picked = await showTimePicker(
diff --git a/lib/ui2/screens/coach_figures.dart b/lib/ui2/screens/coach_figures.dart
index f3953487b..e4ebed452 100644
--- a/lib/ui2/screens/coach_figures.dart
+++ b/lib/ui2/screens/coach_figures.dart
@@ -17,6 +17,7 @@ import 'package:flutter/material.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
 
 import '../../l10n/app_localizations.dart';
+import '../../state/clock_format.dart' show formatClockOf;
 import '../ui2.dart';
 
 // ── loose parsing (the model is not a schema) ────────────────────────────────
@@ -354,8 +355,7 @@ class CoachFigure extends StatelessWidget {
       final d = DateTime.fromMillisecondsSinceEpoch(
         (epochSec * 1000).round(),
       ).toLocal();
-      return '${d.hour.toString().padLeft(2, '0')}:'
-          '${d.minute.toString().padLeft(2, '0')}';
+      return formatClockOf(d);
     }
 
     return _frame(
diff --git a/lib/ui2/screens/ecg.dart b/lib/ui2/screens/ecg.dart
index 8d4697594..b81685a0a 100644
--- a/lib/ui2/screens/ecg.dart
+++ b/lib/ui2/screens/ecg.dart
@@ -20,6 +20,7 @@ import '../../ecg/ecg_models.dart';
 import '../../ecg/ecg_waveform_buffer.dart';
 import '../../l10n/app_localizations.dart';
 import '../../state/app_state.dart';
+import '../../state/clock_format.dart' show formatClockOf;
 import '../../theme/theme_switcher.dart' show themedRoute;
 import '../ui2.dart';
 import 'coach.dart';
@@ -62,7 +63,7 @@ String _wristLabel(AppLocalizations? l, EcgWrist w) => w == EcgWrist.left
 String _fmtWhen(int epochS) {
   final d = DateTime.fromMillisecondsSinceEpoch(epochS * 1000);
   String two(int n) => n.toString().padLeft(2, '0');
-  return '${d.year}-${two(d.month)}-${two(d.day)} ${two(d.hour)}:${two(d.minute)}';
+  return '${d.year}-${two(d.month)}-${two(d.day)} ${formatClockOf(d)}';
 }
 
 // ═══════════════════ entry card (Health overview) ═══════════════════
diff --git a/lib/ui2/screens/home_screen.dart b/lib/ui2/screens/home_screen.dart
index dd6b1bbf9..c874c7012 100644
--- a/lib/ui2/screens/home_screen.dart
+++ b/lib/ui2/screens/home_screen.dart
@@ -42,6 +42,7 @@ import '../../l10n/app_localizations.dart';
 import '../../models/metric.dart';
 import '../../notify/notification_prefs.dart' show NotificationPrefs;
 import '../../state/app_state.dart';
+import '../../state/clock_format.dart' show formatClockOf;
 import '../../state/units_controller.dart';
 import '../../theme/theme_switcher.dart' show themedRoute;
 import '../activity/day_strain.dart' show DayStrainDetail;
@@ -178,9 +179,9 @@ DateTime? lastDataAtOf(BuildContext c) {
 /// directly above it, whatever the hour. Null (no day on screen yet) ⇒ always
 /// dated, which is the honest answer when we do not know what "today" is.
 ///
-/// Bare `HH:mm` for the day on screen, the full "Fri 4 Sep, 07:12" otherwise —
-/// a lone "07:12" against a strap not worn since Friday is the most misleading
-/// thing this line could say.
+/// Bare clock time for the day on screen, the full "Fri 4 Sep, 07:12"
+/// otherwise — a lone "07:12" against a strap not worn since Friday is the
+/// most misleading thing this line could say.
 String syncedThroughLabel(DateTime? at, String? todayId,
     [AppLocalizations? l]) {
   if (at == null) return l?.homeSyncedNever ?? 'No band data yet';
@@ -189,10 +190,7 @@ String syncedThroughLabel(DateTime? at, String? todayId,
       at.year == today.year &&
       at.month == today.month &&
       at.day == today.day;
-  final when = isToday
-      ? '${at.hour.toString().padLeft(2, '0')}:'
-          '${at.minute.toString().padLeft(2, '0')}'
-      : formatDayTime(at, l);
+  final when = isToday ? formatClockOf(at) : formatDayTime(at, l);
   return l?.homeSyncedThrough(when) ?? 'Synced through $when';
 }
 
@@ -596,17 +594,15 @@ String unitBeside(String unit) => unit == 'min' ? '' : unit;
 /// ONE clock format in the app. This used to render 24-hour while Wellness
 /// rendered the same field 12-hour, so a target bedtime read `22:40` on Home
 /// and `10:40 PM` two screens away. Both now go through the journal layer's
-/// [formatMinuteOfDay], which is the format the rest of the app already uses
-/// and the one that already has a test.
+/// [formatMinuteOfDay], which follows the user's 12/24-hour choice
+/// (`state/clock_format.dart`).
 String clock(num? minOfDay) =>
     minOfDay == null ? '' : formatMinuteOfDay(minOfDay.round());
 
-/// Epoch seconds → "11:08 PM" in the device zone.
+/// Epoch seconds → "11:08 PM" / "23:08" in the device zone.
 String clockOfTs(num? ts) {
   if (ts == null) return '';
-  final d = DateTime.fromMillisecondsSinceEpoch(ts.round() * 1000);
-  final h = d.hour % 12 == 0 ? 12 : d.hour % 12;
-  return '$h:${d.minute.toString().padLeft(2, '0')} ${d.hour < 12 ? 'AM' : 'PM'}';
+  return formatClockOf(DateTime.fromMillisecondsSinceEpoch(ts.round() * 1000));
 }
 
 const _months = [
diff --git a/lib/ui2/screens/wellness_screen.dart b/lib/ui2/screens/wellness_screen.dart
index 830f0e7cd..344bc5215 100644
--- a/lib/ui2/screens/wellness_screen.dart
+++ b/lib/ui2/screens/wellness_screen.dart
@@ -1242,8 +1242,7 @@ Future<MedSchedule?> pickMedSchedule(
                       const SizedBox(width: S.x3),
                       Expanded(
                         child: Text(
-                          '${(minute ~/ 60).toString().padLeft(2, '0')}:'
-                          '${(minute % 60).toString().padLeft(2, '0')}',
+                          formatMinuteOfDay(minute),
                           style: F.n17.copyWith(color: p.ink),
                         ),
                       ),
diff --git a/lib/ui2/screens/workout_screen.dart b/lib/ui2/screens/workout_screen.dart
index d0013a836..08e999eb8 100644
--- a/lib/ui2/screens/workout_screen.dart
+++ b/lib/ui2/screens/workout_screen.dart
@@ -27,6 +27,7 @@ import '../../health/health_workout_import.dart';
 import '../../l10n/app_localizations.dart';
 import '../../models/metric.dart';
 import '../../state/app_state.dart';
+import '../../state/clock_format.dart' show formatClockOf;
 import '../../state/units_controller.dart';
 import '../activity/catalogue.dart';
 import '../activity/day_strain.dart';
@@ -1789,8 +1790,7 @@ class _PastWorkout {
       loc?.workoutWeekdayAbbrSat ?? 'Sat',
       loc?.workoutWeekdayAbbrSun ?? 'Sun',
     ];
-    final t = '${start.hour.toString().padLeft(2, '0')}:'
-        '${start.minute.toString().padLeft(2, '0')}';
+    final t = formatClockOf(start);
     if (days == 0) return loc?.workoutWhenToday(t) ?? 'Today, $t';
     if (days == 1) return loc?.workoutWhenYesterday(t) ?? 'Yesterday, $t';
     if (days < 7) return '${names[start.weekday - 1]}, $t';
diff --git a/test/clock_format_test.dart b/test/clock_format_test.dart
new file mode 100644
index 000000000..d02762102
--- /dev/null
+++ b/test/clock_format_test.dart
@@ -0,0 +1,160 @@
+// The 12/24-hour display preference. One formatter for every clock time on
+// screen, so a bedtime cannot read `22:40` on Home and `10:40 PM` two screens
+// away — and so the choice the user makes in Settings reaches all of them.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import 'package:openstrap_edge/data/journal_fields.dart';
+import 'package:openstrap_edge/state/clock_format.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  setUp(() => SharedPreferences.setMockInitialValues({}));
+  tearDown(ClockFormatController.debugReset);
+
+  group('formatClock', () {
+    test('24-hour pads the hour and has no suffix', () {
+      ClockFormatController.seed(ClockFormat.h24);
+      expect(formatClock(0, 0), '00:00');
+      expect(formatClock(7, 5), '07:05');
+      expect(formatClock(12, 0), '12:00');
+      expect(formatClock(23, 59), '23:59');
+    });
+
+    test('12-hour maps midnight and noon to 12', () {
+      ClockFormatController.seed(ClockFormat.h12);
+      expect(formatClock(0, 0), '12:00 AM');
+      expect(formatClock(7, 5), '7:05 AM');
+      expect(formatClock(12, 0), '12:00 PM');
+      expect(formatClock(23, 59), '11:59 PM');
+    });
+
+    test("12-hour uses the app locale's AM/PM and order", () async {
+      ClockFormatController.seed(ClockFormat.h12);
+      Future<void> bind(String lang) async => bindClockLocalizations(
+          await GlobalMaterialLocalizations.delegate.load(Locale(lang)));
+
+      await bind('zh');
+      expect(formatClock(7, 30), '上午 7:30');
+      expect(formatClock(19, 30), '下午 7:30');
+      await bind('es');
+      expect(formatClock(19, 30), '7:30 p. m.');
+      await bind('en');
+      expect(formatClock(19, 30), '7:30 PM');
+    });
+
+    test('minute of day wraps rather than printing an impossible hour', () {
+      ClockFormatController.seed(ClockFormat.h24);
+      expect(formatClockMinute(24 * 60 + 30), '00:30');
+      expect(formatClockMinute(-30), '23:30');
+    });
+
+    test('the journal formatter follows the same choice', () {
+      final c = ClockFormatController.seed(ClockFormat.h12);
+      expect(formatMinuteOfDay(20 * 60 + 30), '8:30 PM');
+      c.setFormat(ClockFormat.h24);
+      expect(formatMinuteOfDay(20 * 60 + 30), '20:30');
+    });
+  });
+
+  group('system', () {
+    test('follows the OS setting, with or without a controller', () {
+      final binding = TestWidgetsFlutterBinding.instance;
+      addTearDown(binding.platformDispatcher
+          .clearAlwaysUse24HourTestValue);
+
+      binding.platformDispatcher.alwaysUse24HourFormatTestValue = true;
+      expect(formatClock(19, 30), '19:30', reason: 'no controller yet');
+      ClockFormatController.seed(ClockFormat.system);
+      expect(formatClock(19, 30), '19:30');
+
+      binding.platformDispatcher.alwaysUse24HourFormatTestValue = false;
+      expect(formatClock(19, 30), '7:30 PM');
+    });
+
+    test('an explicit choice overrides the OS', () {
+      final binding = TestWidgetsFlutterBinding.instance;
+      addTearDown(binding.platformDispatcher
+          .clearAlwaysUse24HourTestValue);
+      binding.platformDispatcher.alwaysUse24HourFormatTestValue = true;
+
+      ClockFormatController.seed(ClockFormat.h12);
+      expect(formatClock(19, 30), '7:30 PM');
+    });
+  });
+
+  group('time picker', () {
+    Future<void> openPicker(WidgetTester tester, {required bool h12}) async {
+      await tester.pumpWidget(MaterialApp(
+        locale: const Locale('de'),
+        supportedLocales: const [Locale('de')],
+        localizationsDelegates: [
+          ClockMaterialLocalizationsDelegate(twelveHour: h12),
+          ...GlobalMaterialLocalizations.delegates,
+        ],
+        builder: (context, child) => MediaQuery(
+          data: MediaQuery.of(context).copyWith(alwaysUse24HourFormat: !h12),
+          child: child!,
+        ),
+        home: Builder(
+          builder: (context) => TextButton(
+            onPressed: () => showTimePicker(
+                context: context,
+                initialTime: const TimeOfDay(hour: 22, minute: 0)),
+            child: const Text('open'),
+          ),
+        ),
+      ));
+      await tester.tap(find.text('open'));
+      await tester.pumpAndSettle();
+    }
+
+    testWidgets('12-hour in German gets an AM/PM dial, still in German',
+        (tester) async {
+      await openPicker(tester, h12: true);
+      expect(find.text('PM'), findsOneWidget);
+      expect(find.text('10'), findsWidgets);
+      expect(find.text('Abbrechen'), findsOneWidget);
+    });
+
+    testWidgets('24-hour in German keeps the 24-hour dial', (tester) async {
+      await openPicker(tester, h12: false);
+      expect(find.text('PM'), findsNothing);
+      expect(find.text('22'), findsWidgets);
+    });
+  });
+
+  group('ClockFormatController', () {
+    test('persists the choice and bootstraps it back', () async {
+      final c = await ClockFormatController.bootstrap();
+      expect(c.format, ClockFormat.system, reason: 'nothing stored yet');
+      await c.setFormat(ClockFormat.h12);
+
+      final again = await ClockFormatController.bootstrap();
+      expect(again.format, ClockFormat.h12);
+    });
+
+    test('an unknown stored value lands on system', () async {
+      SharedPreferences.setMockInitialValues({'clock_format': 'h36'});
+      final c = await ClockFormatController.bootstrap();
+      expect(c.format, ClockFormat.system);
+    });
+
+    test('cycles system → 24-hour → 12-hour → system and notifies', () async {
+      final c = ClockFormatController.seed(ClockFormat.system);
+      var notified = 0;
+      c.addListener(() => notified++);
+      await c.cycle();
+      expect(c.format, ClockFormat.h24);
+      await c.cycle();
+      expect(c.format, ClockFormat.h12);
+      await c.cycle();
+      expect(c.format, ClockFormat.system);
+      expect(notified, 3);
+    });
+  });
+}
diff --git a/test/home_synced_through_test.dart b/test/home_synced_through_test.dart
index db59b8b12..302081648 100644
--- a/test/home_synced_through_test.dart
+++ b/test/home_synced_through_test.dart
@@ -8,11 +8,16 @@
 // read during build decides once and then goes stale across midnight.
 
 import 'package:flutter_test/flutter_test.dart';
+import 'package:openstrap_edge/state/clock_format.dart';
 import 'package:openstrap_edge/ui2/screens/home_screen.dart';
 
 void main() {
   const today = '2026-09-08';
 
+  // The label follows the user's clock format; these pin the 24-hour one.
+  setUp(() => ClockFormatController.seed(ClockFormat.h24));
+  tearDown(ClockFormatController.debugReset);
+
   test('a record from today shows the bare time', () {
     expect(
       syncedThroughLabel(DateTime(2026, 9, 8, 11, 6), today),
diff --git a/test/ui2_wellness_meds_not_due_test.dart b/test/ui2_wellness_meds_not_due_test.dart
index b6269c548..9d68db95f 100644
--- a/test/ui2_wellness_meds_not_due_test.dart
+++ b/test/ui2_wellness_meds_not_due_test.dart
@@ -19,6 +19,7 @@ import 'package:sqflite_common_ffi/sqflite_ffi.dart';
 import 'package:openstrap_edge/data/db.dart';
 import 'package:openstrap_edge/data/med_store.dart';
 import 'package:openstrap_edge/state/app_state.dart';
+import 'package:openstrap_edge/state/clock_format.dart';
 import 'package:openstrap_edge/ui2/screens/screens.dart';
 import 'package:openstrap_edge/ui2/ui2.dart';
 
@@ -29,7 +30,12 @@ void main() {
     sqfliteFfiInit();
     databaseFactory = databaseFactoryFfi;
   });
-  setUp(() => SharedPreferences.setMockInitialValues({}));
+  setUp(() {
+    SharedPreferences.setMockInitialValues({});
+    // The slot time follows the user's clock format; pin the 24-hour one.
+    ClockFormatController.seed(ClockFormat.h24);
+  });
+  tearDown(ClockFormatController.debugReset);
 
   testWidgets('a medication with nothing due today says so', (t) async {
     t.view.physicalSize = const Size(390 * 3, 844 * 3);