Birthdays are great, aren't they? Really, we should have more of them — so why not try to do that by opting to celebrate mathematically significant dates rather than being a slave to the annual event?
Really, birthdays are arbitrary anyway, so you may as well switch to maths. You'll learn something, it will be interesting, and you should (possibly, maybe) receive more presents! Just make sure you can explain the significance of the dates to people by watching this video. [YouTube]