diff --git a/app/components/malio/date/composables/datetimeFormat.test.ts b/app/components/malio/date/composables/datetimeFormat.test.ts
new file mode 100644
index 0000000..70e2b08
--- /dev/null
+++ b/app/components/malio/date/composables/datetimeFormat.test.ts
@@ -0,0 +1,61 @@
+import {describe, expect, it} from 'vitest'
+import {
+  composeDateTime,
+  formatIsoDateTimeToDisplay,
+  isValidIsoDateTime,
+  splitDateTime,
+} from './datetimeFormat'
+
+describe('datetimeFormat', () => {
+  describe('isValidIsoDateTime', () => {
+    it('accepte un datetime ISO complet valide', () => {
+      expect(isValidIsoDateTime('2026-05-20T14:30:00')).toBe(true)
+      expect(isValidIsoDateTime('2026-01-01T00:00:00')).toBe(true)
+      expect(isValidIsoDateTime('2026-12-31T23:59:59')).toBe(true)
+    })
+
+    it('rejette une date seule, des composants invalides ou une chaîne vide', () => {
+      expect(isValidIsoDateTime('2026-05-20')).toBe(false)
+      expect(isValidIsoDateTime('2026-13-01T00:00:00')).toBe(false)
+      expect(isValidIsoDateTime('2026-05-20T24:00:00')).toBe(false)
+      expect(isValidIsoDateTime('2026-05-20T14:60:00')).toBe(false)
+      expect(isValidIsoDateTime('2026-05-20T14:30:60')).toBe(false)
+      expect(isValidIsoDateTime('2026-05-20T14:30')).toBe(false)
+      expect(isValidIsoDateTime('')).toBe(false)
+    })
+  })
+
+  describe('formatIsoDateTimeToDisplay', () => {
+    it('formate un datetime valide en JJ/MM/AAAA HH:MM', () => {
+      expect(formatIsoDateTimeToDisplay('2026-05-20T14:30:00')).toBe('20/05/2026 14:30')
+    })
+
+    it('renvoie une chaîne vide pour nul ou invalide', () => {
+      expect(formatIsoDateTimeToDisplay(null)).toBe('')
+      expect(formatIsoDateTimeToDisplay('2026-05-20')).toBe('')
+      expect(formatIsoDateTimeToDisplay('nope')).toBe('')
+    })
+  })
+
+  describe('splitDateTime', () => {
+    it('découpe un datetime valide', () => {
+      expect(splitDateTime('2026-05-20T14:30:00')).toEqual({date: '2026-05-20', time: '14:30'})
+    })
+
+    it('renvoie date null et time vide pour nul, date seule ou invalide', () => {
+      expect(splitDateTime(null)).toEqual({date: null, time: ''})
+      expect(splitDateTime('2026-05-20')).toEqual({date: null, time: ''})
+      expect(splitDateTime('nope')).toEqual({date: null, time: ''})
+    })
+  })
+
+  describe('composeDateTime', () => {
+    it('recompose un datetime ISO avec secondes à 00', () => {
+      expect(composeDateTime('2026-05-20', '14:30')).toBe('2026-05-20T14:30:00')
+    })
+
+    it('utilise 00:00 quand l\'heure est vide', () => {
+      expect(composeDateTime('2026-05-20', '')).toBe('2026-05-20T00:00:00')
+    })
+  })
+})
diff --git a/app/components/malio/date/composables/datetimeFormat.ts b/app/components/malio/date/composables/datetimeFormat.ts
new file mode 100644
index 0000000..6c6bd6c
--- /dev/null
+++ b/app/components/malio/date/composables/datetimeFormat.ts
@@ -0,0 +1,33 @@
+import {isValidIso} from './dateFormat'
+
+const DATETIME_RE = /^(\d{4}-\d{2}-\d{2})T(\d{2}):(\d{2}):(\d{2})$/
+
+export function isValidIsoDateTime(s: string): boolean {
+  const m = DATETIME_RE.exec(s)
+  if (!m) return false
+  const [, date, hh, mm, ss] = m
+  if (!isValidIso(date)) return false
+  const h = Number(hh)
+  const min = Number(mm)
+  const sec = Number(ss)
+  return h >= 0 && h <= 23 && min >= 0 && min <= 59 && sec >= 0 && sec <= 59
+}
+
+export function formatIsoDateTimeToDisplay(s: string | null): string {
+  if (!s || !isValidIsoDateTime(s)) return ''
+  const [date, time] = s.split('T')
+  const [y, mo, d] = date.split('-')
+  const [hh, mm] = time.split(':')
+  return `${d}/${mo}/${y} ${hh}:${mm}`
+}
+
+export function splitDateTime(s: string | null): {date: string | null; time: string} {
+  if (!s || !isValidIsoDateTime(s)) return {date: null, time: ''}
+  const [date, time] = s.split('T')
+  return {date, time: time.slice(0, 5)}
+}
+
+export function composeDateTime(date: string, time: string): string {
+  const t = time || '00:00'
+  return `${date}T${t}:00`
+}