How to write custom script for optional holidays

In our organization, every year employees can opt-in for 5 optional holidays as festive holidays. Below is the logic for that, how can write a server script for the same. I am going to leave control panel for leave allocation. optional holidays are part of leave policy which also have sick, casual and earned leaves.

01 January 2025 To 01 March 2025 02 March 2025 To 01 May 2025 02 May 2025 To 01 July 2025 02 July 2025 To 31 August 2025 01 September 2025 To 31 October 2025 01 November 2025 To 31 December 2025
5 4 3 2 1 0