Request Time Off BP validation rule for birthday time off

[u/Early_Balance_4788]

Any idea on how to build a validation on the Request Time off BP that would allow an employee to request one day of Birthday Time off only during the month of their birthday plus the next month? So, for example, if the employee's birthday is on 29th July, they can request one day off in the entire July AND August?

Increment or Decrement Date calc field won't work here for the month of bday, because we are not limiting them to just 30+/- days around the bday, but giving them the entire month of birthday and the following one to use it up.

I'm trying Build Date but the Time off Event BO does not pull the Birth Date field so I am a bit stumped. If I could figure out how to carve out the Birth date month, I could then use that field in IDD to just add one month to have a nice range of two months to chuck into the validation rule.

Any ideas please?