# Why do we have leap years?

Happy February 29th!! It's an extra day in the year, are you using it for work or for fun? I'm doing both... but mostly fun! Do you know why we have leap years? Well, it's because with the Gregorian calendar we have a common year that has 365 days. This doesn't match up with the tropical (or solar) year though. A tropical year (the time it takes for the earth to fully orbit the sun) is __365 days, 5 hours, 48 minutes and 45 seconds__. This puts us behind the orbit path by about .2422 days each year, hence the leap year [almost] every four years, so we can keep catching up to the tropical year.

I know, I know, what do I mean "almost" every for years... Well get your thinking cap on, because this is a little tough to track for most people. Leap years happen when the year is evenly divisible by 4, but if the year can also be evenly divided by 100,** it is not a leap year... **unless the year is also evenly divisible by 400.

**Then it**. One more time?

*is*a leap year### Leap year Rule:

The year must be evenly divisible by 4;

If the year can also be evenly divided by 100, it is *not* a leap year;

unless...The year is also evenly divisible by 400. Then it *is* a leap year.

According to these rules, the years 2000 and 2400 were/are leap years,
while 1800, 1900, 2100, 2200, 2300, and 2500 were/are *not* leap years.

And that about sums it up! Thanks for tuning in on this extra day, I hope you found a special use for your catch up day!