Why we have leap days explained via video.

We Have Leap Days Every Four Years, Right? Right?

We Have Leap Days Every Four Years, Right? Right?

Bad Astronomy
The entire universe in blog form
Feb. 28 2016 9:15 AM

Why Do We Have Leap Days? 

Leap day
28 days hath February, except every four years, except every 100 years, except every 400 years.


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



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.”

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

Andrew Bouvé is an Emmy-nominated freelance video producer and motion graphics artist. He lives in Washington, D.C.