feat(settings): add opt-in calendar localization

src-tauri/src/ipc.rs

@@ -202,6 +202,21 @@ pub enum Theme {
     Nord,
 }
 
+#[derive(Clone, Debug, Serialize, Deserialize, TS)]
+#[serde(rename_all = "lowercase")]
+#[ts(export, export_to = "../../src/bindings/")]
+pub enum CalendarPreference {
+    Gregorian,
+    Persian,
+    Hebrew,
+}
+
+impl Default for CalendarPreference {
+    fn default() -> Self {
+        Self::Gregorian
+    }
+}
+
 #[derive(Clone, Debug, Serialize, Deserialize, TS)]
 #[serde(rename_all = "lowercase")]
 #[ts(export, export_to = "../../src/bindings/")]
@@ -267,6 +282,8 @@ pub struct SchedulerSettings {
 #[ts(export, export_to = "../../src/bindings/")]
 pub struct PersistedSettings {
     pub theme: Theme,
+    #[serde(default)]
+    pub calendar_preference: CalendarPreference,
     #[serde(default = "default_language_preference")]
     pub language: String,
     pub base_download_folder: String,

src-tauri/src/settings.rs

@@ -1,6 +1,6 @@
 use crate::ipc::{
-    AppFontSize, ListRowDensity, MediaCookieSource, PersistedSettings, PostQueueAction, ProxyMode,
-    SchedulerSettings, SettingsTab, Theme,
+    AppFontSize, CalendarPreference, ListRowDensity, MediaCookieSource, PersistedSettings,
+    PostQueueAction, ProxyMode, SchedulerSettings, SettingsTab, Theme,
 };
 use serde_json::{Map, Value};
 use std::collections::HashMap;
@@ -197,6 +197,7 @@ fn sanitize_persisted_setting_values(state: &mut Value) {
         "language",
         &["system", "en", "zh-CN", "he", "fa", "uk", "ru"],
     );
+    sanitize_allowed_string(state, "calendarPreference", &["gregorian", "persian", "hebrew"]);
     sanitize_allowed_string(state, "sidebarPosition", &["auto", "left", "right"]);
     sanitize_allowed_string(state, "appFontSize", &["small", "standard", "large"]);
     sanitize_allowed_string(state, "listRowDensity", &["compact", "standard", "relaxed"]);
@@ -416,6 +417,7 @@ fn derived_location_path(base: &str, subfolder: &str) -> String {
 fn default_settings() -> PersistedSettings {
     PersistedSettings {
         theme: Theme::System,
+        calendar_preference: CalendarPreference::Gregorian,
         language: "system".to_string(),
         base_download_folder: "~/Downloads".to_string(),
         category_subfolders_enabled: true,
@@ -703,6 +705,7 @@ mod tests {
                 "perServerConnections": 5,
                 "showNotifications": "yes",
                 "theme": "not-a-theme",
+                "calendarPreference": "lunar",
                 "siteLogins": [{"id": "valid", "urlPattern": "example.com", "username": "user"}, {"id": 3}]
             },
             "version": 3
@@ -715,6 +718,10 @@ mod tests {
         assert_eq!(settings.per_server_connections, 5);
         assert!(settings.show_notifications);
         assert!(matches!(settings.theme, crate::ipc::Theme::System));
+        assert!(matches!(
+            settings.calendar_preference,
+            crate::ipc::CalendarPreference::Gregorian
+        ));
         assert_eq!(settings.site_logins.len(), 1);
         assert_eq!(settings.site_logins[0].id, "valid");
     }

src/bindings/CalendarPreference.ts

@@ -0,0 +1,3 @@
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+
+export type CalendarPreference = "gregorian" | "persian" | "hebrew";

src/bindings/PersistedSettings.ts

@@ -1,5 +1,6 @@
 // This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
 import type { AppFontSize } from "./AppFontSize";
+import type { CalendarPreference } from "./CalendarPreference";
 import type { ListRowDensity } from "./ListRowDensity";
 import type { MediaCookieSource } from "./MediaCookieSource";
 import type { ProxyMode } from "./ProxyMode";
@@ -8,4 +9,4 @@ import type { SettingsTab } from "./SettingsTab";
 import type { SiteLogin } from "./SiteLogin";
 import type { Theme } from "./Theme";
 
-export type PersistedSettings = { theme: Theme, language: string, baseDownloadFolder: string, categorySubfoldersEnabled: boolean, categorySubfolders: { [key in string]: string }, categoryDirectoryOverrides: { [key in string]: string }, approvedDownloadRoots: Array<string>, maxConcurrentDownloads: number, globalSpeedLimit: string, speedLimitPresetValues: Array<number>, logsEnabled: boolean, isSidebarVisible: boolean, sidebarPosition: string, activeSettingsTab: SettingsTab, scheduler: SchedulerSettings, schedulerRunning: boolean, schedulerActiveDownloadIds: Array<string>, schedulerLastStartKey: string, schedulerLastStopKey: string, lastCustomSpeedLimitKiB: number, lastCustomSpeedLimitUnit: string, perServerConnections: number, maxAutomaticRetries: number, showNotifications: boolean, playCompletionSound: boolean, autoAddClipboardLinks: boolean, appFontSize: AppFontSize, listRowDensity: ListRowDensity, showDockBadge: boolean, showMenuBarIcon: boolean, proxyMode: ProxyMode, proxyHost: string, proxyPort: number, customUserAgent: string, askWhereToSaveEachFile: boolean, rememberLastUsedDownloadDirectory: boolean, preventsSleepWhileDownloading: boolean, mediaCookieSource: MediaCookieSource, siteLogins: Array<SiteLogin>, autoCheckUpdates: boolean, keychainAccessGranted: boolean, };
+export type PersistedSettings = { theme: Theme, calendarPreference: CalendarPreference, language: string, baseDownloadFolder: string, categorySubfoldersEnabled: boolean, categorySubfolders: { [key in string]: string }, categoryDirectoryOverrides: { [key in string]: string }, approvedDownloadRoots: Array<string>, maxConcurrentDownloads: number, globalSpeedLimit: string, speedLimitPresetValues: Array<number>, logsEnabled: boolean, isSidebarVisible: boolean, sidebarPosition: string, activeSettingsTab: SettingsTab, scheduler: SchedulerSettings, schedulerRunning: boolean, schedulerActiveDownloadIds: Array<string>, schedulerLastStartKey: string, schedulerLastStopKey: string, lastCustomSpeedLimitKiB: number, lastCustomSpeedLimitUnit: string, perServerConnections: number, maxAutomaticRetries: number, showNotifications: boolean, playCompletionSound: boolean, autoAddClipboardLinks: boolean, appFontSize: AppFontSize, listRowDensity: ListRowDensity, showDockBadge: boolean, showMenuBarIcon: boolean, proxyMode: ProxyMode, proxyHost: string, proxyPort: number, customUserAgent: string, askWhereToSaveEachFile: boolean, rememberLastUsedDownloadDirectory: boolean, preventsSleepWhileDownloading: boolean, mediaCookieSource: MediaCookieSource, siteLogins: Array<SiteLogin>, autoCheckUpdates: boolean, keychainAccessGranted: boolean, };

src/components/DownloadItem.tsx

@@ -4,6 +4,8 @@ import { Play, Pause, MoreVertical, Clock, ArrowUp, ArrowDown, GripVertical } fr
 import type { DownloadItem as DownloadItemType } from '../bindings/DownloadItem';
 import { canPauseDownload, canStartDownload } from '../utils/downloadActions';
 import { useTranslation } from 'react-i18next';
+import { useSettingsStore } from '../store/useSettingsStore';
+import { formatDateTime } from '../utils/dateTime';
 import {
   downloadProgressColorClass,
   formatDownloadTotal,
@@ -59,7 +61,8 @@ export const DownloadItem = React.memo<DownloadItemProps>(({
   onQueueDragStart,
   onClick,
 }) => {
-  const { t } = useTranslation();
+  const { t, i18n } = useTranslation();
+  const calendarPreference = useSettingsStore(state => state.calendarPreference);
   const liveProgress = useDownloadProgressStore(state => state.progressMap[download.id]);
   const rowRef = React.useRef<HTMLDivElement>(null);
   const [isRowHovered, setIsRowHovered] = React.useState(false);
@@ -71,6 +74,12 @@ export const DownloadItem = React.memo<DownloadItemProps>(({
     const normalized = download.mediaQuality.replace(/[\u0000-\u001f\u007f]+/g, ' ').replace(/\s+/g, ' ').trim();
     return normalized.length > 0 && normalized.length <= 48 ? normalized : undefined;
   })();
+  const dateAddedLabel = download.dateAdded
+    ? formatDateTime(download.dateAdded, {
+        locale: i18n.language,
+        calendar: calendarPreference
+      })
+    : '-';
 
   const updateActionPosition = React.useCallback(() => {
     const row = rowRef.current;
@@ -327,9 +336,9 @@ export const DownloadItem = React.memo<DownloadItemProps>(({
       <div className="download-column-cell download-cell-right download-column-date-added" style={columnStyle('Date Added')}>
         <span
           className="download-cell-content download-date-value tabular-nums"
-          title={download.dateAdded ? new Date(download.dateAdded).toLocaleDateString() : '-'}
+          title={dateAddedLabel}
         >
-          {download.dateAdded ? new Date(download.dateAdded).toLocaleDateString() : '-'}
+          {dateAddedLabel}
         </span>
       </div>
     ),

src/components/PropertiesModal.tsx

@@ -18,19 +18,25 @@ import {
 } from '../utils/downloadProgress';
 import { resolveDownloadConnections } from '../utils/downloads';
 import { useTranslation } from 'react-i18next';
+import { formatDateTime, type CalendarPreference } from '../utils/dateTime';
 
 type LoginMode = 'matching' | 'custom' | 'none';
 
-const formatLastTry = (value?: string): string => {
+const formatLastTry = (
+  value: string | undefined,
+  locale: string,
+  calendar: CalendarPreference
+): string => {
   if (!value) return '-';
-  const date = new Date(value);
-  return Number.isNaN(date.getTime())
-    ? '-'
-    : date.toLocaleString(undefined, { dateStyle: 'medium', timeStyle: 'short' });
+  return formatDateTime(value, {
+    locale,
+    calendar,
+    options: { dateStyle: 'medium', timeStyle: 'short' }
+  });
 };
 
 export const PropertiesModal = () => {
-  const { t } = useTranslation();
+  const { t, i18n } = useTranslation();
   const categoryLabel = (category: string) => {
     switch (category) {
       case 'Musics': return t($ => $.navigation.categories.musics);
@@ -55,7 +61,7 @@ export const PropertiesModal = () => {
       : undefined
   ));
 
-  const { baseDownloadFolder, perServerConnections } = useSettingsStore();
+  const { baseDownloadFolder, perServerConnections, calendarPreference } = useSettingsStore();
 
   // Form states
   const [url, setUrl] = useState('');
@@ -373,9 +379,9 @@ export const PropertiesModal = () => {
               <div className="flex gap-1.5 min-w-0"><span className="text-text-muted font-medium shrink-0 whitespace-nowrap">{t($ => $.properties.connections)}</span><span className="text-text-secondary truncate whitespace-nowrap" title={item.connections !== undefined ? t($ => $.properties.savedTooltip) : t($ => $.properties.defaultTooltip)}><bdi>{connectionStatus}</bdi></span></div>
               <div className="flex gap-1.5 min-w-0"><span className="text-text-muted font-medium w-[60px] shrink-0">{t($ => $.properties.speedCap)}</span><span className="text-text-secondary truncate">{item.speedLimit || '-'}</span></div>
               <div className="flex gap-1.5 min-w-0"><span className="text-text-muted font-medium w-[55px] shrink-0">{t($ => $.properties.category)}</span><span className="text-text-secondary truncate">{categoryLabel(item.category)}</span></div>
-            <div className="flex gap-1.5"><span className="text-text-muted font-medium w-[50px]">{t($ => $.properties.lastTry)}</span><span className="text-text-secondary truncate">{formatLastTry(item.lastTry)}</span></div>
+            <div className="flex gap-1.5"><span className="text-text-muted font-medium w-[50px]">{t($ => $.properties.lastTry)}</span><span className="text-text-secondary truncate">{formatLastTry(item.lastTry, i18n.language, calendarPreference)}</span></div>
             
-              <div className="flex gap-1.5 col-span-2"><span className="text-text-muted font-medium w-[90px]">{t($ => $.properties.dateAdded)}</span><span className="text-text-secondary truncate">{new Date(item.dateAdded).toLocaleString(undefined, { dateStyle: 'medium', timeStyle: 'short' })}</span></div>
+              <div className="flex gap-1.5 col-span-2"><span className="text-text-muted font-medium w-[90px]">{t($ => $.properties.dateAdded)}</span><span className="text-text-secondary truncate">{formatDateTime(item.dateAdded, { locale: i18n.language, calendar: calendarPreference, options: { dateStyle: 'medium', timeStyle: 'short' } })}</span></div>
               <div className="flex gap-1.5 col-span-2"><span className="text-text-muted font-medium w-[70px]">{t($ => $.properties.destination)}</span><span className="text-text-secondary truncate" title={saveLocation}>{saveLocation || baseDownloadFolder}</span></div>
             {item.lastError && (item.status === 'failed' || item.status === 'retrying') && (
               <div className="flex gap-1.5 col-span-4 min-w-0">

src/components/SchedulerView.tsx

@@ -11,6 +11,7 @@ import { WindowDragRegion } from './WindowDragRegion';
 import { useToast } from '../contexts/ToastContext';
 import { usePlatformInfo } from '../utils/platform';
 import { useTranslation } from 'react-i18next';
+import { formatDateTime } from '../utils/dateTime';
 
 const days = [
   { value: 0, key: 'su' },
@@ -54,9 +55,10 @@ function nextScheduledRun(settings: SchedulerSettings): Date | 'disabled' | 'non
 }
 
 export default function SchedulerView() {
-  const { t } = useTranslation();
+  const { t, i18n } = useTranslation();
   const savedSettings = useSettingsStore(state => state.scheduler);
   const schedulerRunning = useSettingsStore(state => state.schedulerRunning);
+  const calendarPreference = useSettingsStore(state => state.calendarPreference);
   const setScheduler = useSettingsStore(state => state.setScheduler);
   const queues = useDownloadStore(state => state.queues);
   const [draft, setDraft] = useState<SchedulerSettings>(savedSettings);
@@ -75,14 +77,18 @@ export default function SchedulerView() {
     const scheduledRun = nextScheduledRun(draft);
     if (scheduledRun === 'disabled') return t($ => $.scheduler.disabled);
     if (scheduledRun === 'none') return t($ => $.scheduler.noScheduledDay);
-    return scheduledRun.toLocaleString(undefined, {
-      weekday: 'short',
-      month: 'short',
-      day: 'numeric',
-      hour: 'numeric',
-      minute: '2-digit'
+    return formatDateTime(scheduledRun, {
+      locale: i18n.language,
+      calendar: calendarPreference,
+      options: {
+        weekday: 'short',
+        month: 'short',
+        day: 'numeric',
+        hour: 'numeric',
+        minute: '2-digit'
+      }
     });
-  }, [draft, t]);
+  }, [calendarPreference, draft, i18n.language, t]);
   const hasUnsavedChanges = useMemo(
     () => JSON.stringify(draft) !== JSON.stringify(savedSettings),
     [draft, savedSettings]

src/components/SettingsView.tsx

@@ -693,6 +693,11 @@ runEngineChecks(false);
     { value: 'uk', label: t($ => $.settings.lookAndFeel.languageUkrainian) },
     { value: 'ru', label: t($ => $.settings.lookAndFeel.languageRussian) },
   ] as const;
+  const calendarOptions = [
+    { value: 'gregorian', label: t($ => $.settings.lookAndFeel.calendarGregorian) },
+    { value: 'persian', label: t($ => $.settings.lookAndFeel.calendarPersian) },
+    { value: 'hebrew', label: t($ => $.settings.lookAndFeel.calendarHebrew) },
+  ] as const;
 
   const TabButton = ({ type, icon: Icon, label }: { type: SettingsTab; icon: typeof Download; label: string }) => {
     const active = activeTab === type;
@@ -870,6 +875,21 @@ runEngineChecks(false);
                     ))}
                   </select>
                 </div>
+                <div className="mac-settings-row">
+                  <div className="settings-row-label">
+                    <span>{t($ => $.settings.lookAndFeel.calendar)}</span>
+                    <small>{t($ => $.settings.lookAndFeel.calendarDescription)}</small>
+                  </div>
+                  <select
+                    value={settings.calendarPreference}
+                    onChange={(event) => settings.setCalendarPreference(event.target.value as typeof settings.calendarPreference)}
+                    className="app-control w-48"
+                  >
+                    {calendarOptions.map(option => (
+                      <option key={option.value} value={option.value}>{option.label}</option>
+                    ))}
+                  </select>
+                </div>
                 <div className="mac-settings-row">
                   <div className="settings-row-label">
                     <span>{t($ => $.settings.lookAndFeel.sidebarPosition)}</span>

src/i18n/catalogs/en.ts

@@ -581,6 +581,11 @@ const common = {
       languagePersian: 'Persian',
       languageUkrainian: 'Ukrainian',
       languageRussian: 'Russian',
+      calendar: 'Calendar',
+      calendarDescription: 'Choose the calendar used for displayed dates and times. Gregorian is the default; this does not change scheduling or stored timestamps.',
+      calendarGregorian: 'Gregorian',
+      calendarPersian: 'Persian',
+      calendarHebrew: 'Hebrew',
       appTheme: 'App Theme',
       theme: 'Theme',
       ariaLabel: 'App theme',

src/i18n/catalogs/fa.ts

@@ -581,6 +581,11 @@ const fa = {
       languagePersian: 'فارسی',
       languageUkrainian: 'اوکراینی',
       languageRussian: 'روسی',
+      calendar: 'تقویم',
+      calendarDescription: 'تقویم مورد استفاده برای نمایش تاریخ و زمان را انتخاب کنید. تقویم میلادی پیش‌فرض است و زمان‌بندی یا مُهرهای زمانی ذخیره‌شده را تغییر نمی‌دهد.',
+      calendarGregorian: 'میلادی',
+      calendarPersian: 'هجری شمسی',
+      calendarHebrew: 'عبری',
       appTheme: 'ظاهر برنامه',
       theme: 'ظاهر',
       ariaLabel: 'ظاهر برنامه',

src/i18n/catalogs/he.ts

@@ -581,6 +581,11 @@ const he = {
       languagePersian: 'פרסית',
       languageUkrainian: 'אוקראינית',
       languageRussian: 'רוסית',
+      calendar: 'לוח שנה',
+      calendarDescription: 'בחר את לוח השנה לתצוגת תאריכים ושעות. הלוח הגרגוריאני הוא ברירת המחדל; הבחירה אינה משנה תזמון או חותמות זמן שמורות.',
+      calendarGregorian: 'גרגוריאני',
+      calendarPersian: 'פרסי',
+      calendarHebrew: 'עברי',
       appTheme: 'ערכת נושא לאפליקציה',
       theme: 'ערכת נושא',
       ariaLabel: 'ערכת נושא לאפליקציה',

src/i18n/catalogs/ru.ts

@@ -581,6 +581,11 @@ const ru = {
       languagePersian: 'Персидский',
       languageUkrainian: 'Украинский',
       languageRussian: 'Русский',
+      calendar: 'Календарь',
+      calendarDescription: 'Выберите календарь для отображения дат и времени. По умолчанию используется григорианский; расписание и сохранённые метки времени не изменяются.',
+      calendarGregorian: 'Григорианский',
+      calendarPersian: 'Персидский',
+      calendarHebrew: 'Еврейский',
       appTheme: 'Тема приложения',
       theme: 'Тема',
       ariaLabel: 'Тема приложения',

src/i18n/catalogs/uk.ts

@@ -581,6 +581,11 @@ const uk = {
       languagePersian: 'Перська',
       languageUkrainian: 'Українська',
       languageRussian: 'Російська',
+      calendar: 'Календар',
+      calendarDescription: 'Виберіть календар для відображення дат і часу. Типово використовується григоріанський; розклад і збережені мітки часу не змінюються.',
+      calendarGregorian: 'Григоріанський',
+      calendarPersian: 'Перський',
+      calendarHebrew: 'Єврейський',
       appTheme: 'Тема програми',
       theme: 'Тема',
       ariaLabel: 'Тема програми',

src/i18n/catalogs/zh-CN.ts

@@ -581,6 +581,11 @@ const zhCN = {
       languagePersian: '波斯语',
       languageUkrainian: '乌克兰语',
       languageRussian: '俄语',
+      calendar: '日历',
+      calendarDescription: '选择显示日期和时间所使用的日历。默认使用公历；此选择不会改变计划或已保存的时间戳。',
+      calendarGregorian: '公历',
+      calendarPersian: '波斯历',
+      calendarHebrew: '希伯来历',
       appTheme: '应用主题',
       theme: '主题',
       ariaLabel: '应用主题',

src/store/useSettingsStore.test.ts

@@ -21,6 +21,24 @@ describe('last used download directory preference', () => {
   });
 });
 
+describe('calendar preference', () => {
+  it('keeps Gregorian as the default and persists explicit calendar choices', async () => {
+    vi.clearAllMocks();
+    useSettingsStore.setState({ calendarPreference: 'gregorian' });
+    expect(useSettingsStore.getState().calendarPreference).toBe('gregorian');
+
+    useSettingsStore.getState().setCalendarPreference('persian');
+    await new Promise(resolve => setTimeout(resolve, 0));
+
+    expect(useSettingsStore.getState().calendarPreference).toBe('persian');
+    const save = vi.mocked(ipc.invokeCommand).mock.calls
+      .filter(([command]) => command === 'db_save_settings')
+      .slice(-1)[0];
+    expect(save).toBeDefined();
+    expect(JSON.parse((save?.[1] as { data: string }).data).state.calendarPreference).toBe('persian');
+  });
+});
+
 describe('useSettingsStore global speed limit persistence', () => {
   beforeEach(() => {
     vi.clearAllMocks();

src/store/useSettingsStore.ts

@@ -21,6 +21,11 @@ import {
 import { normalizeSpeedLimitForBackend } from '../utils/downloads';
 import i18n from '../i18n';
 import { isAppLocalePreference, type AppLocalePreference } from '../i18n/locales';
+import {
+  DEFAULT_CALENDAR_PREFERENCE,
+  isCalendarPreference,
+  type CalendarPreference
+} from '../utils/dateTime';
 
 let settingsQueue: Promise<void> = Promise.resolve();
 let pairingTokenHydrationRequest: Promise<PairingTokenHydration> | null = null;
@@ -155,6 +160,7 @@ const tauriStorage: StateStorage = {
 export type {
   ActiveView,
   AppFontSize,
+  CalendarPreference,
   ListRowDensity,
   MediaCookieSource,
   PostQueueAction,
@@ -169,6 +175,7 @@ export type SidebarPosition = 'auto' | 'left' | 'right';
 
 export interface SettingsState {
   theme: Theme;
+  calendarPreference: CalendarPreference;
   language: AppLocalePreference;
   baseDownloadFolder: string;
   categorySubfoldersEnabled: boolean;
@@ -224,6 +231,7 @@ export interface SettingsState {
   showKeychainModal: boolean;
 
   setTheme: (theme: Theme) => void;
+  setCalendarPreference: (calendarPreference: CalendarPreference) => void;
   setLanguage: (language: AppLocalePreference) => void;
   setBaseDownloadFolder: (path: string) => void;
   approveDownloadRoot: (path: string) => Promise<string>;
@@ -280,6 +288,7 @@ export const useSettingsStore = create<SettingsState>()(
   persist(
     (set, get) => ({
       theme: 'system',
+      calendarPreference: DEFAULT_CALENDAR_PREFERENCE,
       language: 'system',
       baseDownloadFolder: '~/Downloads',
       categorySubfoldersEnabled: true,
@@ -342,6 +351,10 @@ export const useSettingsStore = create<SettingsState>()(
       showKeychainModal: false,
 
       setTheme: (theme) => { info('Settings updated: theme'); set({ theme }); },
+      setCalendarPreference: (calendarPreference) => {
+        info('Settings updated: calendarPreference');
+        set({ calendarPreference });
+      },
       setLanguage: (language) => { info('Settings updated: language'); set({ language }); },
       setBaseDownloadFolder: (path) => {
         info('Settings updated: baseDownloadFolder');
@@ -512,7 +525,7 @@ export const useSettingsStore = create<SettingsState>()(
     {
       name: 'firelink-settings',
       storage: createJSONStorage(() => tauriStorage),
-      version: 5,
+      version: 6,
       migrate: (persistedState) => {
         if (!persistedState || typeof persistedState !== 'object') {
           return persistedState as SettingsState;
@@ -548,6 +561,7 @@ export const useSettingsStore = create<SettingsState>()(
       },
       partialize: (state): PersistedSettingsSnapshot => ({
         theme: state.theme,
+        calendarPreference: state.calendarPreference,
         language: state.language,
         baseDownloadFolder: state.baseDownloadFolder,
         categorySubfoldersEnabled: state.categorySubfoldersEnabled,
@@ -608,6 +622,9 @@ export const useSettingsStore = create<SettingsState>()(
           theme: isAllowedSetting(THEME_VALUES, persisted.theme)
             ? persisted.theme
             : currentState.theme,
+          calendarPreference: isCalendarPreference(persisted.calendarPreference)
+            ? persisted.calendarPreference
+            : currentState.calendarPreference,
           language: isAppLocalePreference(persisted.language)
             ? persisted.language
             : currentState.language,

src/utils/dateTime.test.ts

@@ -0,0 +1,35 @@
+import { describe, expect, it } from 'vitest';
+import {
+  DEFAULT_CALENDAR_PREFERENCE,
+  formatDateTime,
+  isCalendarPreference
+} from './dateTime';
+
+describe('date/time formatting', () => {
+  const instant = new Date('2026-03-21T14:30:00.000Z');
+
+  it('uses Gregorian explicitly by default, including in localized UI languages', () => {
+    const options: Intl.DateTimeFormatOptions = { dateStyle: 'medium', timeStyle: 'short' };
+    expect(formatDateTime(instant, { locale: 'fa', options })).toBe(
+      new Intl.DateTimeFormat('fa-u-ca-gregory', options).format(instant)
+    );
+    expect(DEFAULT_CALENDAR_PREFERENCE).toBe('gregorian');
+  });
+
+  it('supports the opt-in Persian and Hebrew calendars', () => {
+    const options: Intl.DateTimeFormatOptions = { dateStyle: 'long' };
+    expect(formatDateTime(instant, { locale: 'fa', calendar: 'persian', options })).toBe(
+      new Intl.DateTimeFormat('fa-u-ca-persian', options).format(instant)
+    );
+    expect(formatDateTime(instant, { locale: 'he', calendar: 'hebrew', options })).toBe(
+      new Intl.DateTimeFormat('he-u-ca-hebrew', options).format(instant)
+    );
+  });
+
+  it('returns a safe placeholder for malformed timestamps and rejects unknown preferences', () => {
+    expect(formatDateTime('not-a-timestamp', { locale: 'en' })).toBe('-');
+    expect(isCalendarPreference('gregorian')).toBe(true);
+    expect(isCalendarPreference('lunar')).toBe(false);
+    expect(isCalendarPreference(null)).toBe(false);
+  });
+});

src/utils/dateTime.ts

@@ -0,0 +1,65 @@
+import type { CalendarPreference } from '../bindings/CalendarPreference';
+import { resolveAppLocale } from '../i18n/locales';
+
+export type { CalendarPreference } from '../bindings/CalendarPreference';
+
+export const CALENDAR_PREFERENCES = ['gregorian', 'persian', 'hebrew'] as const satisfies readonly CalendarPreference[];
+export const DEFAULT_CALENDAR_PREFERENCE: CalendarPreference = 'gregorian';
+
+export const isCalendarPreference = (value: unknown): value is CalendarPreference =>
+  typeof value === 'string' && (CALENDAR_PREFERENCES as readonly string[]).includes(value);
+
+type DateTimeInput = Date | string | number;
+
+interface DateTimeFormatConfig {
+  locale?: string | null;
+  calendar?: CalendarPreference;
+  options?: Intl.DateTimeFormatOptions;
+}
+
+const calendarIdentifier = (calendar: CalendarPreference): string =>
+  calendar === 'gregorian' ? 'gregory' : calendar;
+
+const localeWithCalendar = (locale: string | null | undefined, calendar: CalendarPreference): string => {
+  const resolvedLocale = resolveAppLocale(locale);
+  return `${resolvedLocale}-u-ca-${calendarIdentifier(calendar)}`;
+};
+
+const dateFromInput = (value: DateTimeInput): Date =>
+  value instanceof Date ? new Date(value.getTime()) : new Date(value);
+
+/**
+ * Format a user-facing timestamp with an explicit calendar. Gregorian is
+ * passed explicitly because some localized browser defaults use a regional
+ * calendar even when the user has not opted into one.
+ */
+export const formatDateTime = (
+  value: DateTimeInput,
+  config: DateTimeFormatConfig = {}
+): string => {
+  const date = dateFromInput(value);
+  if (Number.isNaN(date.getTime())) return '-';
+
+  const calendar = config.calendar && isCalendarPreference(config.calendar)
+    ? config.calendar
+    : DEFAULT_CALENDAR_PREFERENCE;
+  const options = config.options ?? {};
+
+  try {
+    return new Intl.DateTimeFormat(
+      localeWithCalendar(config.locale, calendar),
+      options
+    ).format(date);
+  } catch {
+    // WebViews can have incomplete ICU calendar data. Keep the display useful
+    // and deterministic rather than exposing a RangeError to the UI.
+    try {
+      return new Intl.DateTimeFormat(
+        localeWithCalendar(config.locale, DEFAULT_CALENDAR_PREFERENCE),
+        options
+      ).format(date);
+    } catch {
+      return '-';
+    }
+  }
+};