feat: Add Holidays feature to block availability on public holidays (calcom#25561)

* feat: add holidays feature for automatic availability blocking- Add UserHolidaySettings model for storing user preferences- Generate static holiday data for 20 countries using date-holidays- Create HolidayService for runtime holiday queries- Add TRPC router with endpoints for country selection and holiday toggles- Create Holidays tab UI in Availability page with conflict warnings- Integrate holiday blocking into getUserAvailability calculation- Show holiday indicator on blocked dates in booker page- Add warning in OOO modal when dates overlap with holidays

* feat: add optimizations, tests, and code quality improvements

- Add memoization/caching to HolidayService for better performance
- Optimize checkConflicts DB query with OR conditions for specific dates
- Add HolidayService unit tests (10 tests)
- Add error handling with Alert component for failed queries
- Memoize HolidayListItem component to prevent unnecessary re-renders
- Extract magic numbers into constants.ts
- Use TRPCError consistently in handlers
- Add missing i18n keys for error messages
- Update handlers to follow Cal.com patterns (default exports, minimal comments)
- Add regeneration instructions in constants

* refactor: replace static JSON with Google Calendar API integration

- Add GoogleHolidayService to fetch holidays from Google Calendar public calendars
- Add HolidayCache Prisma model for caching API responses
- Add GOOGLE_CALENDAR_API_KEY and HOLIDAY_CACHE_DAYS env variables
- Support 38 countries via Google Calendar holiday calendars
- Update HolidayService methods to async with database caching
- Update all TRPC handlers for async holiday methods
- Fix UI to display holiday dates correctly
- Remove static holidays.json and generate script

* use we instead of calcom in i18n message

* address cubics comments

* move holidays from availability to ooo

* public holidays filter for holidays

* follow i18n _one and _other pattern

* remove holiday feature flag

* revert lint command code change

* revert lint command code change 2.0

* revert lint command code change 3.0

* bye bye my christmas emoji :crying-emoji

* remove comments

* refactor(holidays): add repository pattern, split services, and add tests

- Create HolidayRepository for database operations
- Split GoogleHolidayService into GoogleCalendarClient and HolidayCacheService
- Add dependency injection to HolidayService and HolidayCacheService
- Update TRPC handlers to use HolidayRepository
- Add tests for HolidayRepository and calculateHolidayBlockedDates
- Update calendar IDs to use official holiday format (244 countries + religions)

* fix: address PR review feedback

- Remove unused date-holidays package
- Add pluralization for and_more_holidays_with_conflicts translation
- DRY: spread GOOGLE_RELIGIOUS_HOLIDAY_CALENDARS into GOOGLE_HOLIDAY_CALENDARS
- Add select to userHolidaySettings query in getUserAvailability
- Optimize checkConflicts with pre-computed timestamps

* refactor(holidays): apply proxy pattern and move logic to service

- Rename HolidayCacheService to HolidayServiceCachingProxy (proxy pattern)
- Remove HOLIDAY_CACHE_DAYS env var, use constant directly
- Add isSupportedCountry() method to HolidayService
- Add getUserSettings() and updateSettings() to HolidayService
- Move toggleHoliday logic from handler to service
- Move checkConflicts logic from handler to service
- Add findBookingsInDateRanges() to HolidayRepository
- Simplify all handlers to just call service methods

* feat(bookings): add backend validation to prevent booking on holidays

Adds explicit holiday conflict validation during booking creation to
handle the race condition where a host enables a holiday after a guest
selects a date but before they submit the booking.

Changes:
- Add checkHolidayConflict validation with HolidayRepository integration
- Integrate ensureNoHolidayConflict in RegularBookingService
- Add BookingOnHoliday error code with proper HTTP 400 response
- Handle holiday error display in BookEventForm with name interpolation
- Hide trace ID for expected validation errors
- Add unit tests for holiday conflict validation

* fix failing type check

* fix: address PR review comments for holiday feature

- Change error code from BAD_REQUEST to INTERNAL_SERVER_ERROR in
  toggleHoliday handler (errors are internal failures, not bad input)
- Refactor ensureNoHolidayConflict to use Promise.all for parallel
  user checking instead of sequential loop

* refactor: use Promise.all with logging in loop for holiday check

- Check all users in parallel using Promise.all
- Log conflicts inside the loop as they are detected
- Wait for all checks to complete before throwing error

* fix(holidays): use host timezone for holiday conflict checks

The holiday feature was checking booking dates against holidays using
server/local timezone instead of the host's timezone. This caused
bookings near midnight boundaries to incorrectly pass or fail the
holiday check.

Example: A booking at Dec 24th 8PM UTC (which is Dec 25th in IST)
was not being blocked for an Indian host with Christmas as a holiday.

Changes:
- Add .utc() to holiday date formatting for consistency
- Fetch host's timezone in checkHolidayConflict
- Convert booking time to host's timezone before comparison
- Add findUserSettingsWithTimezone to HolidayRepository
- Update error message to clarify it's the host's local time
- Add timezone edge case tests

* fix(holidays): align holiday blocking with OOO pattern for consistent timezone handling

- Simplify calculateHolidayBlockedDates to match OOO pattern using dayjs.utc()
- Fix date range query to use full day bounds (startOfDay/endOfDay) so holidays
  stored at midnight UTC are correctly found during booking validation
- Remove separate checkHolidayConflict booking-time validation - holidays now
  block through oooExcludedDateRanges like OOO does
- Remove getHolidayOnDate from HolidayService (no longer needed)
- Remove findUserSettingsWithTimezone from HolidayRepository (no longer needed)
- Clean up related tests

Holiday blocking now works exactly like OOO:
1. Holidays are added to datesOutOfOffice in calculateHolidayBlockedDates
2. buildDateRanges processes them via processOOO with .tz(timeZone, true)
3. oooExcludedDateRanges excludes those dates from availability
4. ensureAvailableUsers uses oooExcludedDateRanges to block bookings

This ensures consistent timezone handling where Dec 25th blocks all hours
of Dec 25th in the host's timezone, regardless of booker's timezone.

* update test

* update .env.example file

Author: dhairyashiil

.env.example

@@ -127,6 +127,14 @@ NEXT_PUBLIC_HELPSCOUT_KEY=
 NEXT_PUBLIC_FRESHCHAT_TOKEN=
 NEXT_PUBLIC_FRESHCHAT_HOST=
 
+# For holiday feature:
+# Step-by-step: Get a Google Calendar API Key
+# 1. Go to Google Cloud Console: https://console.cloud.google.com/
+# 2. Select or Create a Project
+# 3. Enable Google Calendar API (APIs & Services → Library , Search for Google Calendar API)
+# 4. Create the API Key (APIs & Services → Credentials)
+GOOGLE_CALENDAR_API_KEY=
+
 # Google OAuth credentials
 # To enable Login with Google you need to:
 # 1. Set `GOOGLE_API_CREDENTIALS` below

apps/web/modules/settings/my-account/out-of-office-view.tsx

@@ -4,9 +4,11 @@ import { useEffect, useState } from "react";
 
 import { useCompatSearchParams } from "@calcom/lib/hooks/useCompatSearchParams";
 
-import OutOfOfficeEntriesList from "@calcom/features/settings/outOfOffice/OutOfOfficeEntriesList";
 import { CreateOrEditOutOfOfficeEntryModal } from "@calcom/features/settings/outOfOffice/CreateOrEditOutOfOfficeModal";
 import type { BookingRedirectForm } from "@calcom/features/settings/outOfOffice/CreateOrEditOutOfOfficeModal";
+import { HolidaysView } from "@calcom/features/settings/outOfOffice/HolidaysView";
+import OutOfOfficeEntriesList from "@calcom/features/settings/outOfOffice/OutOfOfficeEntriesList";
+import { OutOfOfficeTab } from "@calcom/features/settings/outOfOffice/OutOfOfficeToggleGroup";
 
 export default function OutOfOfficeView() {
   const [openModal, setOpenModal] = useState(false);
@@ -15,6 +17,7 @@ export default function OutOfOfficeView() {
 
   const params = useCompatSearchParams();
   const openModalOnStart = !!params?.get("om");
+  const selectedTab = params?.get("type") ?? OutOfOfficeTab.MINE;
 
   useEffect(() => {
     if (openModalOnStart) {
@@ -37,6 +40,11 @@ export default function OutOfOfficeView() {
     setCurrentlyEditingOutOfOfficeEntry(null);
   };
 
+  // Show HolidaysView when holidays tab is selected
+  if (selectedTab === OutOfOfficeTab.HOLIDAYS) {
+    return <HolidaysView />;
+  }
+
   return (
     <>
       <OutOfOfficeEntriesList

apps/web/pages/api/trpc/holidays/[trpc].ts

@@ -0,0 +1,4 @@
+import { createNextApiHandler } from "@calcom/trpc/server/createNextApiHandler";
+import { holidaysRouter } from "@calcom/trpc/server/routers/viewer/holidays/_router";
+
+export default createNextApiHandler(holidaysRouter);

apps/web/public/static/locales/en/common.json

@@ -4110,6 +4110,26 @@
   "booking_response": "Booking Response",
   "list_view": "List view",
   "calendar_view": "Calendar view",
+  "holidays": "Holidays",
+  "holidays_description": "We will automatically mark you as unavailable for the selected holidays",
+  "country_for_holidays": "Country for holidays",
+  "select_country": "Select country",
+  "no_holidays": "No holidays",
+  "holidays_list": "Holidays",
+  "no_holidays_selected": "No holidays selected",
+  "select_country_to_see_holidays": "Select a country to see available holidays",
+  "holiday_settings_updated": "Holiday settings updated",
+  "holiday_no_availability": "No availability on this holiday",
+  "holiday_booking_conflict_warning_one": "You have {{count}} booking on holidays",
+  "holiday_booking_conflict_warning_other": "You have {{count}} bookings on holidays",
+  "holiday_overlap_info": "Holiday notice",
+  "holiday_overlap_message_single": "{{date}} is {{holiday}}, which is already blocked as a holiday",
+  "holiday_overlap_message_multiple": "{{count}} days in this range are holidays ({{holidays}})",
+  "no_holidays_found_for_country": "No holidays found for this country.",
+  "booking_count_one": "{{count}} booking",
+  "booking_count_other": "{{count}} bookings",
+  "and_more_holidays_with_conflicts_one": "... and {{count}} more holiday with conflicts",
+  "and_more_holidays_with_conflicts_other": "... and {{count}} more holidays with conflicts",
   "assignment_reason": "Assignment Reason",
   "saved": "Saved",
   "booking_history": "Booking History",