If you are born on February 29 or a leapling your birthday changes each year.

Most people say you'd age every 4 years but you still aged 365 days/1 year. So 365 days after February 29 is March 1, meaning your new birthday would be March 1 and not Feb. 29. So for the rest of your life, your birthday will be different almost every year due to your 365th day living. So next time you have a type of anniversary on Feb 29, you'll know about this 1 day difference.

Source:
http://en.wikipedia.org/wiki/February_29