Holiday Entitlement - Pro Rata

Hello,

I'm currently setting up new job titles on Fourth based on a new hotel our company will manage. With this, we are honouring their current terms and conditions. 

Long service holiday entitlement is rewarded. This is one additional day per year worked (up to 5 years). Holiday Year is Jan to Dec.

However, they also have a stipulation that if their year anniversary falls after the start of the holiday year, they are entitled to a pro rata amount.

Jan to May - full additional day
June to Sep - half additional day 
Oct to Dec - no additional day 

i.e. if someone started in Feb 2024, they will celebrate a year in Feb 2025. Currently the set up is they would only receive the additional day in Feb 2026 (after a full year) but they should receive a full additional day as of Jan 2025. 

Because I can't amend the global settings as we have other locations with other T&Cs, I'm trying to find the best way to set this up (if at all possible). I thought perhaps using decimals (i.e. 0.5 Years - additional day) but when I've tested this, it rounds to the nearest full number. 

Any ideas would be greatly appreciated as don't want to go down the manual route of updating each year! 

Thanks,

Emily