diff --git a/apps/portal/pages/admin/scheduling.vue b/apps/portal/pages/admin/scheduling.vue
index ba4125d..7215ea8 100644
--- a/apps/portal/pages/admin/scheduling.vue
+++ b/apps/portal/pages/admin/scheduling.vue
@@ -25,6 +25,7 @@ interface EventType {
   maximumDaysInFuture: number
   availabilityScheduleId: string
   locationType: string
+  ignoreAllDayEvents: boolean
   isActive: boolean
 }
 interface MinuteInterval { startMinute: number; endMinute: number }
@@ -258,6 +259,7 @@ const etForm = reactive({
   maximumDaysInFuture: 60,
   availabilityScheduleId: '',
   locationType: 'jitsi',
+  ignoreAllDayEvents: true,
 })
 const etEditingId = ref<string | null>(null)
 const etSlugTouched = ref(false)
@@ -271,7 +273,7 @@ function openEt(et?: EventType) {
       slotIntervalMinutes: et.slotIntervalMinutes, bufferBeforeMinutes: et.bufferBeforeMinutes,
       bufferAfterMinutes: et.bufferAfterMinutes, minimumNoticeMinutes: et.minimumNoticeMinutes,
       maximumDaysInFuture: et.maximumDaysInFuture, availabilityScheduleId: et.availabilityScheduleId,
-      locationType: et.locationType,
+      locationType: et.locationType, ignoreAllDayEvents: et.ignoreAllDayEvents ?? true,
     })
     etSlugTouched.value = true // don't auto-rewrite an existing slug
   } else {
@@ -280,6 +282,7 @@ function openEt(et?: EventType) {
       title: '', slug: '', durationMinutes: 30, slotIntervalMinutes: 15,
       bufferBeforeMinutes: 0, bufferAfterMinutes: 0, minimumNoticeMinutes: 60,
       maximumDaysInFuture: 60, availabilityScheduleId: availability.value[0]?._id ?? '', locationType: 'jitsi',
+      ignoreAllDayEvents: true,
     })
     etSlugTouched.value = false
   }
@@ -608,6 +611,10 @@ const detailTabs = computed(() => [
             <option value="in_person">In person</option><option value="custom">Custom</option>
           </select>
         </label>
+        <label class="daytoggle">
+          <input type="checkbox" v-model="etForm.ignoreAllDayEvents" />
+          Ignore all-day events when checking availability
+        </label>
       </div>
       <template #footer>
         <UiButton variant="ghost" @click="etOpen = false">Cancel</UiButton>
diff --git a/services/platform-api/src/scheduling/event-types/dto/event-type-dtos.ts b/services/platform-api/src/scheduling/event-types/dto/event-type-dtos.ts
index 346b471..72cc5a3 100644
--- a/services/platform-api/src/scheduling/event-types/dto/event-type-dtos.ts
+++ b/services/platform-api/src/scheduling/event-types/dto/event-type-dtos.ts
@@ -1,4 +1,5 @@
 import {
+  IsBoolean,
   IsEnum,
   IsHexColor,
   IsInt,
@@ -80,6 +81,10 @@ export class CreateEventTypeDto {
   @IsOptional()
   @IsHexColor()
   color?: string
+
+  @IsOptional()
+  @IsBoolean()
+  ignoreAllDayEvents?: boolean
 }
 
 // All fields optional for PATCH. (Avoids a mapped-types dependency.)
@@ -96,4 +101,5 @@ export class UpdateEventTypeDto {
   @IsOptional() @IsEnum(LOCATIONS) locationType?: LocationType
   @IsOptional() @IsString() @MaxLength(500) locationDetails?: string
   @IsOptional() @IsHexColor() color?: string
+  @IsOptional() @IsBoolean() ignoreAllDayEvents?: boolean
 }
diff --git a/services/platform-api/src/scheduling/event-types/event-types.service.ts b/services/platform-api/src/scheduling/event-types/event-types.service.ts
index 66f4e53..b3b2b24 100644
--- a/services/platform-api/src/scheduling/event-types/event-types.service.ts
+++ b/services/platform-api/src/scheduling/event-types/event-types.service.ts
@@ -17,6 +17,7 @@ export interface EventTypeInput {
   locationType?: LocationType
   locationDetails?: string
   color?: string
+  ignoreAllDayEvents?: boolean
 }
 
 @Injectable()
diff --git a/services/platform-api/src/scheduling/slots/slot.service.ts b/services/platform-api/src/scheduling/slots/slot.service.ts
index 4ea4685..c6955f0 100644
--- a/services/platform-api/src/scheduling/slots/slot.service.ts
+++ b/services/platform-api/src/scheduling/slots/slot.service.ts
@@ -37,7 +37,9 @@ export class SlotService {
 
     let calendarBusy
     try {
-      calendarBusy = await this.gateway.getBusyIntervals(access, fromUtc, toUtc)
+      calendarBusy = await this.gateway.getBusyIntervals(access, fromUtc, toUtc, {
+        ignoreAllDayEvents: eventType.ignoreAllDayEvents,
+      })
     } catch {
       throw new ServiceUnavailableException('Calendar is temporarily unavailable — please retry.')
     }
diff --git a/services/platform-api/src/scheduling/stalwart-calendar/calendar-gateway.types.ts b/services/platform-api/src/scheduling/stalwart-calendar/calendar-gateway.types.ts
index 3f8ec3b..bbd7553 100644
--- a/services/platform-api/src/scheduling/stalwart-calendar/calendar-gateway.types.ts
+++ b/services/platform-api/src/scheduling/stalwart-calendar/calendar-gateway.types.ts
@@ -37,10 +37,18 @@ export interface BookingEvent {
   attendeeEmail: string
 }
 
+// Per-call tuning for free/busy resolution.
+export interface BusyOptions {
+  // When true, all-day events are excluded from the returned busy intervals
+  // (best-effort — see JmapCalendarGateway.getBusyIntervals). Default false:
+  // every busy marker counts.
+  ignoreAllDayEvents?: boolean
+}
+
 export interface CalendarGateway {
   listCalendars(access: HostCalendarAccess): Promise<CalendarRef[]>
   // Busy intervals within [fromUtc, toUtc), recurrence already expanded, in UTC.
-  getBusyIntervals(access: HostCalendarAccess, fromUtc: Date, toUtc: Date): Promise<Interval[]>
+  getBusyIntervals(access: HostCalendarAccess, fromUtc: Date, toUtc: Date, options?: BusyOptions): Promise<Interval[]>
   // Returns the server-assigned event id (distinct from the UID).
   createEvent(access: HostCalendarAccess, event: BookingEvent): Promise<{ uid: string; id: string }>
   deleteEvent(access: HostCalendarAccess, eventId: string): Promise<void>
diff --git a/services/platform-api/src/scheduling/stalwart-calendar/jmap-calendar.gateway.ts b/services/platform-api/src/scheduling/stalwart-calendar/jmap-calendar.gateway.ts
index e5ee971..d659eef 100644
--- a/services/platform-api/src/scheduling/stalwart-calendar/jmap-calendar.gateway.ts
+++ b/services/platform-api/src/scheduling/stalwart-calendar/jmap-calendar.gateway.ts
@@ -1,6 +1,7 @@
 import { Injectable, Logger } from '@nestjs/common'
 import type {
   BookingEvent,
+  BusyOptions,
   CalendarGateway,
   CalendarRef,
   HostCalendarAccess,
@@ -88,7 +89,12 @@ export class JmapCalendarGateway implements CalendarGateway {
     return list.map((c) => ({ id: c.id, name: c.name }))
   }
 
-  async getBusyIntervals(access: HostCalendarAccess, fromUtc: Date, toUtc: Date): Promise<Interval[]> {
+  async getBusyIntervals(
+    access: HostCalendarAccess,
+    fromUtc: Date,
+    toUtc: Date,
+    options?: BusyOptions,
+  ): Promise<Interval[]> {
     const session = await this.session(access)
     const accountId = this.calAccountId(session)
     const resp = await this.call(
@@ -109,9 +115,85 @@ export class JmapCalendarGateway implements CalendarGateway {
     }
     const list = (out[1]?.list ?? []) as Array<{ utcStart: string; utcEnd: string; busyStatus?: string }>
     // Drop free/tentative-cancelled markers; count confirmed + tentative as busy.
-    return list
+    const busy = list
       .filter((b) => b.busyStatus !== 'free')
       .map((b) => ({ startUtc: new Date(b.utcStart), endUtc: new Date(b.utcEnd) }))
+
+    if (!options?.ignoreAllDayEvents) return busy
+
+    // Best-effort all-day exclusion. Principal/getAvailability collapses every
+    // event to a plain UTC interval with no all-day flag (Phase 0 finding —
+    // reference_stalwart_calendar_jmap), so we cannot tell an all-day event from
+    // a same-length timed event by its busy interval alone. To honour the flag we
+    // separately query CalendarEvent over the window and read each event's
+    // showWithoutTime / date-only `start` to recognise all-day events, then drop
+    // any busy interval that an all-day event covers.
+    //
+    // This is intentionally fail-soft: if the (occasionally flaky) CalendarEvent
+    // query errors, we keep ALL busy intervals (fail toward over-blocking, never
+    // toward a double-book) rather than propagating and breaking slot computation.
+    try {
+      const allDay = await this.allDayIntervals(access, accountId, fromUtc, toUtc)
+      if (allDay.length === 0) return busy
+      return busy.filter((b) => !allDay.some((ad) => coversInterval(ad, b)))
+    } catch (err) {
+      this.logger.warn(
+        `ignoreAllDayEvents: all-day detection failed for ${access.email}, keeping all busy intervals: ${(err as Error).message}`,
+      )
+      return busy
+    }
+  }
+
+  // Returns the UTC spans of all-day events in [fromUtc, toUtc). An all-day event
+  // in JSCalendar is signalled by showWithoutTime:true and/or a date-only `start`
+  // ("YYYY-MM-DD") with no `timeZone`; multi-day all-day events carry a P..D
+  // duration. We expand each to [start-of-day, start-of-day + duration) in the
+  // event's local zone (falling back to UTC), which is enough to overlap-match
+  // the busy intervals getAvailability produced for the same events.
+  private async allDayIntervals(
+    access: HostCalendarAccess,
+    accountId: string,
+    fromUtc: Date,
+    toUtc: Date,
+  ): Promise<Interval[]> {
+    const resp = await this.call(
+      access,
+      [CORE, CALENDARS],
+      [
+        [
+          'CalendarEvent/query',
+          {
+            accountId,
+            filter: { before: toUtc.toISOString(), after: fromUtc.toISOString() },
+          },
+          'q',
+        ],
+        [
+          'CalendarEvent/get',
+          {
+            accountId,
+            '#ids': { resultOf: 'q', name: 'CalendarEvent/query', path: '/ids' },
+            properties: ['start', 'duration', 'timeZone', 'showWithoutTime', 'recurrenceOverrides'],
+          },
+          'g',
+        ],
+      ],
+    )
+    const got = resp.find((r) => r[0] === 'CalendarEvent/get')
+    if (!got) return []
+    const events = (got[1]?.list ?? []) as Array<{
+      start?: string
+      duration?: string
+      timeZone?: string
+      showWithoutTime?: boolean
+    }>
+    const out: Interval[] = []
+    for (const ev of events) {
+      if (!isAllDay(ev)) continue
+      const span = allDaySpan(ev)
+      if (span) out.push(span)
+    }
+    return out
   }
 
   async createEvent(access: HostCalendarAccess, event: BookingEvent): Promise<{ uid: string; id: string }> {
@@ -197,6 +279,73 @@ function toJsCalLocal(utc: Date, tz: string): string {
   return `${get('year')}-${get('month')}-${get('day')}T${hour}:${get('minute')}:${get('second')}`
 }
 
+// True if a JSCalendar event represents an all-day event: either the explicit
+// showWithoutTime flag, or a date-only `start` ("YYYY-MM-DD" with no time part).
+function isAllDay(ev: { start?: string; showWithoutTime?: boolean }): boolean {
+  if (ev.showWithoutTime === true) return true
+  return typeof ev.start === 'string' && /^\d{4}-\d{2}-\d{2}$/.test(ev.start)
+}
+
+// Convert an all-day event to a concrete UTC interval. `start` is a local date
+// (date-only) or local date-time; `duration` defaults to one day. We anchor the
+// span at local midnight in the event's zone (or UTC if absent) so it overlaps
+// the busy interval getAvailability emitted for the same event.
+function allDaySpan(ev: { start?: string; duration?: string; timeZone?: string }): Interval | null {
+  if (!ev.start) return null
+  const datePart = ev.start.slice(0, 10)
+  if (!/^\d{4}-\d{2}-\d{2}$/.test(datePart)) return null
+  const startUtc = localMidnightToUtc(datePart, ev.timeZone)
+  if (!startUtc) return null
+  const days = Math.max(1, durationToDays(ev.duration))
+  const endUtc = new Date(startUtc.getTime() + days * 86_400_000)
+  return { startUtc, endUtc }
+}
+
+// Interpret "YYYY-MM-DD" at 00:00 in `tz` (default UTC) as a UTC instant. We
+// derive the zone offset for that date via Intl and subtract it from the naive
+// UTC midnight.
+function localMidnightToUtc(date: string, tz?: string): Date | null {
+  const naive = new Date(`${date}T00:00:00Z`)
+  if (Number.isNaN(naive.getTime())) return null
+  if (!tz) return naive
+  try {
+    const offsetMs = zoneOffsetMs(naive, tz)
+    return new Date(naive.getTime() - offsetMs)
+  } catch {
+    return naive
+  }
+}
+
+// Offset (ms) of `tz` from UTC at instant `at` (positive east of UTC).
+function zoneOffsetMs(at: Date, tz: string): number {
+  const parts = new Intl.DateTimeFormat('en-US', {
+    timeZone: tz,
+    year: 'numeric', month: '2-digit', day: '2-digit',
+    hour: '2-digit', minute: '2-digit', second: '2-digit',
+    hour12: false,
+  }).formatToParts(at)
+  const get = (t: string) => Number(parts.find((p) => p.type === t)?.value ?? '0')
+  const hour = get('hour') === 24 ? 0 : get('hour')
+  const asUtc = Date.UTC(get('year'), get('month') - 1, get('day'), hour, get('minute'), get('second'))
+  return asUtc - at.getTime()
+}
+
+// Whole days in an ISO-8601 duration like "P2D" / "P1W". All-day events use
+// day/week granularity; sub-day parts (PT..) round up to at least one day.
+function durationToDays(duration?: string): number {
+  if (!duration) return 1
+  const weeks = Number(/(\d+)W/.exec(duration)?.[1] ?? 0)
+  const days = Number(/(\d+)D/.exec(duration)?.[1] ?? 0)
+  const total = weeks * 7 + days
+  return total > 0 ? total : 1
+}
+
+// True if all-day interval `ad` fully covers busy interval `b` (so `b` is the
+// busy span of an all-day event and should be dropped when ignoring all-day).
+function coversInterval(ad: Interval, b: Interval): boolean {
+  return ad.startUtc.getTime() <= b.startUtc.getTime() && ad.endUtc.getTime() >= b.endUtc.getTime()
+}
+
 // Milliseconds → ISO-8601 duration (whole minutes are enough for bookings).
 function isoDuration(ms: number): string {
   const totalMinutes = Math.round(ms / 60000)
diff --git a/services/platform-api/src/schemas/event-type.schema.ts b/services/platform-api/src/schemas/event-type.schema.ts
index 0f6126f..18c187e 100644
--- a/services/platform-api/src/schemas/event-type.schema.ts
+++ b/services/platform-api/src/schemas/event-type.schema.ts
@@ -59,6 +59,12 @@ export class EventType {
   @Prop({ trim: true })
   color?: string
 
+  // When true (default), all-day calendar events on the host's calendar are NOT
+  // treated as busy — so e.g. an all-day "On leave" marker or a holiday does not
+  // block every slot of the day. Set false to honour all-day events as busy.
+  @Prop({ default: true })
+  ignoreAllDayEvents!: boolean
+
   @Prop({ default: true, index: true })
   isActive!: boolean
 }