Leap Year also known as Topsy Turvy day

[The Shirt]

Edward - that's because you hate all the birthday fuss! You'd only have to avoid it once every 4 years then.

 

[Sunny]

I believe they switch the birthday to February 28 or March 1, but they technically are 4 years old when they turn 1. If that makes sense.

If you want to be really technical, they'll still be the actual number of years old, but only have celebrated X number of birthDAYS. A year still = 365.24... (whatever) days, no matter what. To be super-technical, on non-leap years, they'd calculate the days and hours and celebrate on the day when their birth TIME falls.

That sounds like a lot of math...