You could add Holidays to your Freshdesk Business Calendar or remove specific dates from the Holiday Calendar.
Yearly holiday list can be configured by adding specific dates to the holiday calendar. This could be done from under Admin > Team > Business Hours > Edit > Holidays, where you can add a date to your holiday calendar.
Change calendar holidays:
Kindly navigate to Admin > Team > Business Hours > Edit > and under the Holidays section, you could remove a specific Holiday from the list.