So, in order to make up for errors in the Calendar, today is the 29th Feb, when an extra day is added to the year to straighten things out.
One thing I do loathe about Leap years is, people who are born on the 29th February like to have a good old laugh about being 'only 5 years old,' or similar when they're 20 chronologically.
I'd shut them up by saying "So you're 5 then? In that case it is illegal for you to drink, have sex, vote, drive etc etc!" Now pick your jaw back off the floor and go and play with your Lego, child.