Restricted absences are just that; periods of time where people are not permitted to book time off. This is often used during critical periods for the business, such as the financial year end.
If you have been assigned the Configuration Manager role within the Absences application, you'll see the ‘Mandatory Absence’ option in the Configuration Menu. Clicking on this option will give you the default absence plan upon which you can define Mandatory or Restricted dates.
Select the applicable dates from the calendar and then select the option ‘No one can take time off’.