Why Do We Have Leap Days? 

Usually, there are only four Mondays in February. But this year’s February is weird^*: It’ll have five Mondays.

Why?

It’s leap year!

A lot of folks get confused on why exactly we even have leap years. The answer is simple.

Wait! No, it’s not! It’s actually a mess. But together with the good folks at Slate I have tried to simplify it for you in video form:

See? Now, in that video I skipped a few things, and rounded the numbers a lot to make it easier to grasp. If you want the details—and it’s math, so it’s fun, and you do—wait until Monday, and I’ll have an article up with lots of details. You’ll be glad you have an extra day this month to figure it all out.

^*You know what’s weirder than having five Mondays in February? Having that first “r” in “February.”