Self-hosted
Configuration
Rooms
Sessions
User Management
Bookings
Holidays are periods of time - either a single date or date range - where bookings can't be made. They apply to all users, for all periods and in all rooms.

The dates are inclusive, so only enter the dates that are part of the holiday itself.
Holidays are part of the session, so the holiday's dates must be within the date range of the session itself.