Can I configure the expiration date of a year's holidays?

Of course you can! You will be able to set the date on which the holidays not taken in a given year will expire.

When you create a holidays calendar configuration, you will be able to choose whether to edit this expiration date or not. If so, you will choose the exact date after which your employees will not be able to take their holidays.

To do so, follow this path: Configuration >> Calendars >> Holidays >> Create >> Maximum days >> Configure vacation expiration date.