You will need to enter the Holiday (or Bank Holiday) at Admin > Config > Core Set up and click on Holidays. At the bottom of the page, select the particular Holiday, Bank Holiday or staff Training Day from the Holiday dropdown menu and enter the start and end dates. If it is a Bank Holiday the start and end date will be the same date.
Do not enter a weekend date as a start or end date. The registers will open the next week day after the end date provided.