To change the start/end date and default number of days for Holiday Allowance in your organisation (appears on Resources), custom settings for Holiday Allowance must be edited in Preempt Global Settings.
Go to Setup.
Use the search bar to find Preempt Global Settings.
Click on Manage button.
Click on Global.
Click on the Edit button.
Search for Holiday Allowance (Use Ctrl+F). You can change the End Date (1) and the Start Date (2) of the period for which Holiday Allowance will be calculated and the default number of days of Holiday Allowance (3) in your organisation.
Click on Save.