fix(time): use Intl numeric day-month-year everywhere so chat day dividers follow the system locale instead of hardcoded English full-month

src/app/components/room-intro/RoomIntro.tsx

@@ -7,7 +7,7 @@ import { getMemberDisplayName, getStateEvent } from '../../utils/room';
 import { useMatrixClient } from '../../hooks/useMatrixClient';
 import { getMxIdLocalPart, mxcUrlToHttp } from '../../utils/matrix';
 import { AsyncStatus, useAsyncCallback } from '../../hooks/useAsyncCallback';
-import { timeDayMonthYear, timeHourMinute } from '../../utils/time';
+import { timeDayMonYear, timeHourMinute } from '../../utils/time';
 import { useRoomNavigate } from '../../hooks/useRoomNavigate';
 import { RoomAvatar } from '../room-avatar';
 import { nameInitials } from '../../utils/common';
@@ -75,7 +75,7 @@ export const RoomIntro = as<'div', RoomIntroProps>(({ room, ...props }, ref) =>
                 i18nKey="Room.created_by"
                 values={{
                   creator: creatorName,
-                  date: timeDayMonthYear(ts),
+                  date: timeDayMonYear(ts),
                   time: timeHourMinute(ts),
                 }}
                 components={{ bold: <b /> }}

src/app/features/room/RoomTimeline.tsx

@@ -105,7 +105,7 @@ import { markAsRead } from '../../utils/notifications';
 import { useDebounce } from '../../hooks/useDebounce';
 import { getResizeObserverEntry, useResizeObserver } from '../../hooks/useResizeObserver';
 import * as css from './RoomTimeline.css';
-import { inSameDay, minuteDifference, timeDayMonthYear, today, yesterday } from '../../utils/time';
+import { inSameDay, minuteDifference, timeDayMonYear, today, yesterday } from '../../utils/time';
 import { isEmptyEditor } from '../../components/editor';
 import { draftKey, roomIdToReplyDraftAtomFamily } from '../../state/room/roomInputDrafts';
 import { usePowerLevelsContext } from '../../hooks/usePowerLevels';
@@ -2211,7 +2211,7 @@ export function RoomTimeline({
     const dayLabel = (() => {
       if (today(mEvent.getTs())) return t('Room.today');
       if (yesterday(mEvent.getTs())) return t('Room.yesterday');
-      return timeDayMonthYear(mEvent.getTs());
+      return timeDayMonYear(mEvent.getTs());
     })();
 
     const renderDayDivider = () => (

src/app/features/room/jump-to-time/JumpToTime.tsx

@@ -28,7 +28,7 @@ import { useAlive } from '../../../hooks/useAlive';
 import { useStateEvent } from '../../../hooks/useStateEvent';
 import { useRoom } from '../../../hooks/useRoom';
 import { StateEvent } from '../../../../types/matrix/room';
-import { getToday, getYesterday, timeDayMonthYear, timeHourMinute } from '../../../utils/time';
+import { getToday, getYesterday, timeDayMonYear, timeHourMinute } from '../../../utils/time';
 import { DatePicker, TimePicker } from '../../../components/time-date';
 
 type JumpToTimeProps = {
@@ -168,7 +168,7 @@ export function JumpToTime({ onCancel, onSubmit }: JumpToTimeProps) {
                       after={<Icon size="50" src={Icons.ChevronBottom} />}
                       onClick={handleDatePicker}
                     >
-                      <Text size="B300">{timeDayMonthYear(ts)}</Text>
+                      <Text size="B300">{timeDayMonYear(ts)}</Text>
                     </Chip>
                     <PopOut
                       anchor={datePickerCords}

src/app/utils/time.ts

@@ -26,9 +26,20 @@ const detectSystemHour24 = (): boolean => {
 
 export const SYSTEM_HOUR_24: boolean = detectSystemHour24();
 
-// 24-hour systems get the European day-month-year layout; 12-hour systems get
+// Locale picks its own day-month-year order and separator: de-DE/ru-RU yield
-// the American month-day-year layout.
+// "13.05.2026", en-GB "13/05/2026", en-US "05/13/2026". Built once at module
-const SYSTEM_DAY_MON_YEAR_FORMAT = SYSTEM_HOUR_24 ? 'DD/MM/YYYY' : 'MM/DD/YYYY';
+// load — locale doesn't change without a page reload.
+const dayMonYearFormatter: Pick<Intl.DateTimeFormat, 'format'> = (() => {
+  try {
+    return new Intl.DateTimeFormat(undefined, {
+      day: '2-digit',
+      month: '2-digit',
+      year: 'numeric',
+    });
+  } catch {
+    return { format: (date: Date) => dayjs(date).format('DD.MM.YYYY') };
+  }
+})();
 
 export const today = (ts: number): boolean => dayjs(ts).isToday();
 
@@ -45,9 +56,7 @@ export const timeYear = (ts: number): string => dayjs(ts).format('YYYY');
 export const timeHourMinute = (ts: number): string =>
   dayjs(ts).format(SYSTEM_HOUR_24 ? 'HH:mm' : 'hh:mm A');
 
-export const timeDayMonYear = (ts: number): string => dayjs(ts).format(SYSTEM_DAY_MON_YEAR_FORMAT);
+export const timeDayMonYear = (ts: number): string => dayMonYearFormatter.format(new Date(ts));
-
-export const timeDayMonthYear = (ts: number): string => dayjs(ts).format('D MMMM YYYY');
 
 export const daysInMonth = (month: number, year: number): number =>
   dayjs(`${year}-${month}-1`).daysInMonth();