I feel like celebrating on March 1st when it's not a leap year makes the most sense. If someone was born on February 29, then their birthday is the day after February 28.
I feel like celebrating on February 28th when it's not a leap year makes the most sense. If someone was born on February 29, then their birthday is the day before March 1.
I feel like celebrating only on February 29th during a leap year makes the most sense. If someone was born on February 29, then that's their birthday and their rate of aging is slowed by %80.
A year, basically, since you were born after the 28th but also before the 1st, so the next year before the first would already be a year again. Mar 1st would be a year and a day, technically.
If you want to argue for celebrating on the 28th, I would argue that you are actually 1 year older the day before your birthday. That is why you can buy alcohol the day before you turn 21. At least where I live.