F8: Date formatting uses Intl per app language

formatDate special-cased only French, so Danish users saw US
mm/dd/yyyy; formatDateTime mixed a manual French format with
toLocaleString() (OS-locale dependent) for everyone else. Both now use
Intl.DateTimeFormat with a fixed app-language -> BCP-47 map (en-US,
fr-FR, da-DK — same mapping as useSpeech), 2-digit day/month so output
stays deterministic per language: en 03/15/2026, fr 15/03/2026,
da 15.03.2026. Adds a Danish format test.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/utils/dateFormatter.js

@@ -1,20 +1,24 @@
 import i18next from 'i18next'
 
+// App language → BCP-47 tag (same mapping as useSpeech.js). Fixed tags keep
+// the output deterministic per app language regardless of the OS locale, so
+// tests can assert it (en: 03/15/2026, fr: 15/03/2026, da: 15.03.2026).
+const LANG_MAP = { en: 'en-US', fr: 'fr-FR', da: 'da-DK' }
+
+function toLangTag(lang) {
+  return LANG_MAP[lang || i18next.language] || LANG_MAP.en
+}
+
 export function formatDate(date, lang) {
   if (!date) return ''
   const d = date instanceof Date ? date : new Date(date)
   if (isNaN(d.getTime())) return ''
 
-  lang = lang || i18next.language || 'en'
-  const pad = (n) => String(n).padStart(2, '0')
-  const dd = pad(d.getDate())
-  const mm = pad(d.getMonth() + 1)
-  const yyyy = d.getFullYear()
-
-  if (lang === 'fr') {
-    return `${dd}/${mm}/${yyyy}`
-  }
-  return `${mm}/${dd}/${yyyy}`
+  return new Intl.DateTimeFormat(toLangTag(lang), {
+    day: '2-digit',
+    month: '2-digit',
+    year: 'numeric',
+  }).format(d)
 }
 
 export function formatItemDuration(ms) {
@@ -46,17 +50,12 @@ export function formatDateTime(date, lang) {
   const d = date instanceof Date ? date : new Date(date)
   if (isNaN(d.getTime())) return ''
 
-  lang = lang || i18next.language || 'en'
-  const pad = (n) => String(n).padStart(2, '0')
-  const dd = pad(d.getDate())
-  const mm = pad(d.getMonth() + 1)
-  const yyyy = d.getFullYear()
-  const HH = pad(d.getHours())
-  const min = pad(d.getMinutes())
-  const ss = pad(d.getSeconds())
-
-  if (lang === 'fr') {
-    return `${dd}/${mm}/${yyyy}, ${HH}:${min}:${ss}`
-  }
-  return d.toLocaleString()
+  return new Intl.DateTimeFormat(toLangTag(lang), {
+    day: '2-digit',
+    month: '2-digit',
+    year: 'numeric',
+    hour: '2-digit',
+    minute: '2-digit',
+    second: '2-digit',
+  }).format(d)
 }

tests/test_step9_stats.py

@@ -4,6 +4,7 @@ Step 9 — Statistics
 - test_stats_shows_empty_when_no_date: StatsView shows empty message when no creation date
 - test_stats_date_format_english: Date is formatted as MM/DD/YYYY in English
 - test_stats_date_format_french: Date is formatted as DD/MM/YYYY in French
+- test_stats_date_format_danish: Date is formatted as DD.MM.YYYY in Danish
 - test_stats_date_format_updates_on_language_change: Switching language updates the date format reactively
 - test_stats_date_range_tabs_visible: All four date range tabs are rendered
 - test_stats_summary_cards_zero_when_no_data: Summary cards show 0 when no execution logs exist
@@ -240,6 +241,28 @@ def test_stats_date_format_french(page: Page, app_url: str):
     page.wait_for_timeout(300)
 
 
+def test_stats_date_format_danish(page: Page, app_url: str):
+    """Date is formatted as DD.MM.YYYY in Danish (not the US fallback)."""
+    _set_date_and_reload(page, app_url, _KNOWN_DATE)
+
+    page.click('a[href="#/settings"]')
+    page.wait_for_url("**/#/settings", timeout=5000)
+    page.wait_for_selector('[data-testid="settings-language"]')
+    page.select_option('[data-testid="settings-language"]', 'da')
+    page.wait_for_timeout(500)
+
+    _go_to_stats(page)
+
+    text = page.locator('[data-testid="stats-using-since"]').text_content()
+    assert '15.03.2026' in text, f"Expected Danish date format, got: {text}"
+
+    page.click('a[href="#/settings"]')
+    page.wait_for_url("**/#/settings", timeout=5000)
+    page.wait_for_selector('[data-testid="settings-language"]')
+    page.select_option('[data-testid="settings-language"]', 'en')
+    page.wait_for_timeout(300)
+
+
 def test_stats_date_format_updates_on_language_change(page: Page, app_url: str):
     """Switching language updates the date format reactively without navigation."""
     _set_date_and_reload(page, app_url, _KNOWN_DATE)