To add an absence for multiple days, go to Operations - Time Card. Select the dates you want to add absences for and click Add absences:
Adding absences for multiple days in Timecard in Astrow Web
Add/Edit absence window opens and you can make the absence for the days selected:
Adding / editing absences for multiple days in Timecard in Astrow Web
You can also include the non-working days when adding the absence.
The functionality of adding absences for multiple days is available only with ESS license and Self Edit Absences permission. It is also important to set in Configuration - System - Application config. the maximum days for self edit bookings / absences for the past and future.