Blackout dates are days which your employees won't be allowed to book any leave on.
On the settings menu click Calendar, then click Blackout dates.
Click Add blackout day.
Enter the name of a period you want to blackout.
Select dates for your blackout period.
Select which employees you want this blackout period to apply to.
Here you can select any policies that you want to override your blackout date e.g Sick Leave.
These blackout dates now appear on your calendar.