What Is a Leap Year?

As it turns out, there are people who don't quite understand the concept of a leap year. And while I was looking for pictures to post on this entry, I discovered that I wasn't aware that there is some movie by the same name. I wasn't impressed by the trailer, so why don't we take it one step at a time and just resolve for now the more important and interesting question regarding the astronomical concept of a leap year with a quick, fun and educational animation?

And if today is your birthday, happy leap birthday! Hope you feel younger than the rest of us.