Happy March! You may have noticed that this past February we had an extra day—February 29th. That’s because 2016 is a leap year. Every four years, we add an extra day to February because our normal 365-day year isn’t quite long enough to match up with the exact amount of time it takes the Earth to make one full rotation around the sun. But, it’s actually a bit more complicated than that. Check out this video of Neil DeGrasse Tyson, an American astrophysicist and author, explaining how leap years work and why we have them.