diff --git a/i18n/en.json b/i18n/en.json
index a25d62e94c8..a43d288954b 100644
--- a/i18n/en.json
+++ b/i18n/en.json
@@ -694,6 +694,7 @@
   "daily_title_text_date": "E, MMM dd",
   "daily_title_text_date_year": "E, MMM dd, yyyy",
   "dark": "Dark",
+  "darkTheme": "Toggle dark theme",
   "date_after": "Date after",
   "date_and_time": "Date and Time",
   "date_before": "Date before",
@@ -1817,7 +1818,6 @@
   "to_parent": "Go to parent",
   "to_trash": "Trash",
   "toggle_settings": "Toggle settings",
-  "toggle_theme": "Toggle dark theme",
   "total": "Total",
   "total_usage": "Total usage",
   "trash": "Trash",
diff --git a/web/src/lib/components/shared-components/theme-button.svelte b/web/src/lib/components/shared-components/theme-button.svelte
index 74937703402..17b0b539ee0 100644
--- a/web/src/lib/components/shared-components/theme-button.svelte
+++ b/web/src/lib/components/shared-components/theme-button.svelte
@@ -1,13 +1,20 @@
 <script lang="ts">
-  import { Theme } from '$lib/constants';
+  import { defaultLang, langs, Theme } from '$lib/constants';
   import { themeManager } from '$lib/managers/theme-manager.svelte';
+  import { lang } from '$lib/stores/preferences.store';
   import { ThemeSwitcher } from '@immich/ui';
+  import { get } from 'svelte/store';
 </script>
 
 {#if !themeManager.theme.system}
-  <ThemeSwitcher
-    size="medium"
-    color="secondary"
-    onChange={(theme) => themeManager.setTheme(theme == 'dark' ? Theme.DARK : Theme.LIGHT)}
-  />
+  {#await langs
+    .find((item) => item.code === get(lang))
+    ?.loader() ?? defaultLang.loader() then { default: translations }}
+    <ThemeSwitcher
+      size="medium"
+      color="secondary"
+      {translations}
+      onChange={(theme) => themeManager.setTheme(theme == 'dark' ? Theme.DARK : Theme.LIGHT)}
+    />
+  {/await}
 {/if}
diff --git a/web/src/lib/components/user-settings-page/app-settings.svelte b/web/src/lib/components/user-settings-page/app-settings.svelte
index adb37d5d939..d248038a240 100644
--- a/web/src/lib/components/user-settings-page/app-settings.svelte
+++ b/web/src/lib/components/user-settings-page/app-settings.svelte
@@ -39,7 +39,7 @@
   };
 
   const handleToggleLocaleBrowser = () => {
-    $locale = $locale ? undefined : fallbackLocale.code;
+    $locale = $locale === 'default' ? fallbackLocale.code : 'default';
   };
 
   const handleLocaleChange = (newLocale: string | undefined) => {
@@ -89,13 +89,13 @@
         <SettingSwitch
           title={$t('default_locale')}
           subtitle={$t('default_locale_description')}
-          checked={$locale == undefined}
+          checked={$locale == 'default'}
           onToggle={handleToggleLocaleBrowser}
         >
           <p class="mt-2 dark:text-gray-400">{selectedDate}</p>
         </SettingSwitch>
       </div>
-      {#if $locale !== undefined}
+      {#if $locale !== 'default'}
         <div class="ms-4">
           <SettingCombobox
             comboboxPlaceholder={$t('searching_locales')}
@@ -113,7 +113,6 @@
           title={$t('display_original_photos')}
           subtitle={$t('display_original_photos_setting_description')}
           bind:checked={$alwaysLoadOriginalFile}
-          onToggle={() => ($alwaysLoadOriginalFile = !$alwaysLoadOriginalFile)}
         />
       </div>
       <div class="ms-4">
@@ -121,16 +120,10 @@
           title={$t('video_hover_setting')}
           subtitle={$t('video_hover_setting_description')}
           bind:checked={$playVideoThumbnailOnHover}
-          onToggle={() => ($playVideoThumbnailOnHover = !$playVideoThumbnailOnHover)}
         />
       </div>
       <div class="ms-4">
-        <SettingSwitch
-          title={$t('loop_videos')}
-          subtitle={$t('loop_videos_description')}
-          bind:checked={$loopVideo}
-          onToggle={() => ($loopVideo = !$loopVideo)}
-        />
+        <SettingSwitch title={$t('loop_videos')} subtitle={$t('loop_videos_description')} bind:checked={$loopVideo} />
       </div>
 
       <div class="ms-4">
diff --git a/web/src/lib/constants.ts b/web/src/lib/constants.ts
index fdb18b39781..ae53b4e7f3f 100644
--- a/web/src/lib/constants.ts
+++ b/web/src/lib/constants.ts
@@ -273,9 +273,17 @@ export const locales = [
   { code: 'zu-ZA', name: 'Zulu (South Africa)' },
 ];
 
-export const defaultLang = { name: 'English', code: 'en', loader: () => import('$i18n/en.json') };
+interface Lang {
+  name: string;
+  code: string;
+  loader: () => Promise<{ default: object }>;
+  rtl?: boolean;
+  weblateCode?: string;
+}
 
-export const langs = [
+export const defaultLang: Lang = { name: 'English', code: 'en', loader: () => import('$i18n/en.json') };
+
+export const langs: Lang[] = [
   { name: 'Afrikaans', code: 'af', loader: () => import('$i18n/af.json') },
   { name: 'Arabic', code: 'ar', loader: () => import('$i18n/ar.json'), rtl: true },
   { name: 'Azerbaijani', code: 'az', loader: () => import('$i18n/az.json'), rtl: true },
@@ -359,7 +367,7 @@ export const langs = [
     weblateCode: 'zh_SIMPLIFIED',
     loader: () => import('$i18n/zh_SIMPLIFIED.json'),
   },
-  { name: 'Development (keys only)', code: 'dev', loader: () => Promise.resolve({}) },
+  { name: 'Development (keys only)', code: 'dev', loader: () => Promise.resolve({ default: {} }) },
 ];
 
 export enum ImmichProduct {
diff --git a/web/src/lib/stores/preferences.store.ts b/web/src/lib/stores/preferences.store.ts
index e7f38eb6d08..f0689e5d6e6 100644
--- a/web/src/lib/stores/preferences.store.ts
+++ b/web/src/lib/stores/preferences.store.ts
@@ -9,9 +9,9 @@ export interface ThemeSetting {
 }
 
 // Locale to use for formatting dates, numbers, etc.
-export const locale = persisted<string | undefined>('locale', undefined, {
+export const locale = persisted<string | undefined>('locale', 'default', {
   serializer: {
-    parse: (text) => (text == '' ? 'en-US' : text),
+    parse: (text) => text || 'default',
     stringify: (object) => object ?? '',
   },
 });
diff --git a/web/src/lib/utils/timeline-util.spec.ts b/web/src/lib/utils/timeline-util.spec.ts
index f842b948e06..c77aefc0b49 100644
--- a/web/src/lib/utils/timeline-util.spec.ts
+++ b/web/src/lib/utils/timeline-util.spec.ts
@@ -1,3 +1,4 @@
+import { locale } from '$lib/stores/preferences.store';
 import { parseUtcDate } from '$lib/utils/date-time';
 import { formatGroupTitle } from '$lib/utils/timeline-util';
 import { DateTime } from 'luxon';
@@ -16,48 +17,63 @@ describe('formatGroupTitle', () => {
 
   it('formats today', () => {
     const date = parseUtcDate('2024-07-27T01:00:00Z');
-    expect(formatGroupTitle(date.setLocale('en'))).toBe('today');
-    expect(formatGroupTitle(date.setLocale('es'))).toBe('hoy');
+    locale.set('en');
+    expect(formatGroupTitle(date)).toBe('today');
+    locale.set('es');
+    expect(formatGroupTitle(date)).toBe('hoy');
   });
 
   it('formats yesterday', () => {
     const date = parseUtcDate('2024-07-26T23:59:59Z');
-    expect(formatGroupTitle(date.setLocale('en'))).toBe('yesterday');
-    expect(formatGroupTitle(date.setLocale('fr'))).toBe('hier');
+    locale.set('en');
+    expect(formatGroupTitle(date)).toBe('yesterday');
+    locale.set('fr');
+    expect(formatGroupTitle(date)).toBe('hier');
   });
 
   it('formats last week', () => {
     const date = parseUtcDate('2024-07-21T00:00:00Z');
-    expect(formatGroupTitle(date.setLocale('en'))).toBe('Sunday');
-    expect(formatGroupTitle(date.setLocale('ar-SA'))).toBe('الأحد');
+    locale.set('en');
+    expect(formatGroupTitle(date)).toBe('Sunday');
+    locale.set('ar-SA');
+    expect(formatGroupTitle(date)).toBe('الأحد');
   });
 
   it('formats date 7 days ago', () => {
     const date = parseUtcDate('2024-07-20T00:00:00Z');
-    expect(formatGroupTitle(date.setLocale('en'))).toBe('Sat, Jul 20');
-    expect(formatGroupTitle(date.setLocale('de'))).toBe('Sa., 20. Juli');
+    locale.set('en');
+    expect(formatGroupTitle(date)).toBe('Sat, Jul 20');
+    locale.set('de');
+    expect(formatGroupTitle(date)).toBe('Sa., 20. Juli');
   });
 
   it('formats date this year', () => {
     const date = parseUtcDate('2020-01-01T00:00:00Z');
-    expect(formatGroupTitle(date.setLocale('en'))).toBe('Wed, Jan 1, 2020');
-    expect(formatGroupTitle(date.setLocale('ja'))).toBe('2020年1月1日(水)');
+    locale.set('en');
+    expect(formatGroupTitle(date)).toBe('Wed, Jan 1, 2020');
+    locale.set('ja');
+    expect(formatGroupTitle(date)).toBe('2020年1月1日(水)');
   });
 
   it('formats future date', () => {
     const tomorrow = parseUtcDate('2024-07-28T00:00:00Z');
-    expect(formatGroupTitle(tomorrow.setLocale('en'))).toBe('Sun, Jul 28');
+    locale.set('en');
+    expect(formatGroupTitle(tomorrow)).toBe('Sun, Jul 28');
 
     const nextMonth = parseUtcDate('2024-08-28T00:00:00Z');
-    expect(formatGroupTitle(nextMonth.setLocale('en'))).toBe('Wed, Aug 28');
+    locale.set('en');
+    expect(formatGroupTitle(nextMonth)).toBe('Wed, Aug 28');
 
     const nextYear = parseUtcDate('2025-01-10T12:00:00Z');
-    expect(formatGroupTitle(nextYear.setLocale('en'))).toBe('Fri, Jan 10, 2025');
+    locale.set('en');
+    expect(formatGroupTitle(nextYear)).toBe('Fri, Jan 10, 2025');
   });
 
   it('returns "Invalid DateTime" when date is invalid', () => {
     const date = DateTime.invalid('test');
-    expect(formatGroupTitle(date.setLocale('en'))).toBe('Invalid DateTime');
-    expect(formatGroupTitle(date.setLocale('es'))).toBe('Invalid DateTime');
+    locale.set('en');
+    expect(formatGroupTitle(date)).toBe('Invalid DateTime');
+    locale.set('es');
+    expect(formatGroupTitle(date)).toBe('Invalid DateTime');
   });
 });
diff --git a/web/src/lib/utils/timeline-util.ts b/web/src/lib/utils/timeline-util.ts
index d8252271a22..7538e0e02c1 100644
--- a/web/src/lib/utils/timeline-util.ts
+++ b/web/src/lib/utils/timeline-util.ts
@@ -62,12 +62,12 @@ export function formatGroupTitle(_date: DateTime): string {
 
   // Today
   if (today.hasSame(date, 'day')) {
-    return date.toRelativeCalendar();
+    return date.toRelativeCalendar({ locale: get(locale) });
   }
 
   // Yesterday
   if (today.minus({ days: 1 }).hasSame(date, 'day')) {
-    return date.toRelativeCalendar();
+    return date.toRelativeCalendar({ locale: get(locale) });
   }
 
   // Last week