Why do we have a
leap year? Why do we have a
leap year?
Hmmmmm....
Our calendars have 365 days, right? Right. We call that particular cycle from January 1 through December 31 our "calendar year". It's just about equal to the time it takes us to orbit our sun. But, is our calendar year really 365 days long? Nope! Here's why.
The Earth actually takes a tad longer to make a complete orbit around the sun. It takes 365.25 (or 365 and "one-quarter") days to orbit the sun once (one quarter of a day is equal to 6 hours). That's called our "solar year". But our calendars are only 365 days long. Uh oh, that's a problem. It's pretty darn hard to put a quarter of a day on a calendar, never mind try to live a quarter of a day. As the years go by - 1st, 2nd, 3rd - we become more and more out of step with the our calendars. By the 4th year, we have "gotten ahead" of our calendars by one full day.
So, to keep us from getting too far ahead of our calendars (which, by the way, really did happen and you can read about it on this web site) every four years we add an extra full day to our calendars to keep them up-to-date with our solar year. We call this extra day a "leap day", and the year it falls on a "leap year". If we didn't do this, we'd really be in trouble. Our seasons would get all changed around. Pretty soon, well not too soon, but in about 720 years or so, our seasons would be about 6 months out-of-step with the calendars.
If you lived in the northern hemisphere, your calendar would be showing December, but in reality, it would be like a warm summers day because the Earth would actually be positioned with respect to the sun for the middle of July!
If you lived in the southern hemisphere, your calendar would be showing December as well (which is really your summertime) but it would be cold because the Earths actual position with respect to the sun would be for July, which is your wintertime.
Well, it's a good thing someone came up with the idea
to put a leap day in our calendars and a leap year we can have fun with. 
Rivet! Do you know who that certain someone is? (The answer is
on this site) That extra day puts us back in step with our calendars and all set for
another four years. Isn't that something? Rivet!
Hey! How'd that frog get in here?
