Hello Leila:
Since Leap Years are any year that can be evenly divided by 4 (such as 2012, 2016, etc) except if it can can be evenly divided by 100, then it isn't (such as 2100, 2200, etc) and except if it can be evenly divided by 400, then it is (such as 2000, 2400) maybe you could work out a PCR calculation that work this out?
Cheers.
Antoine