The Scientific Secrets Behind February 29

It's more complex than you thought

We all know that there are 24 hours in a day, 365 days in a year, except for leap years, when there's an extra day added onto the end of February. 

But why do we even have them?

A full spin around the sun is actually a quarter of a day longer than we account for, and inserting an extra day into the mix every 4 years keeps things on track. 

This may seem a bit confusing and li more trouble than it's worth, but needing to keep track of the days of the year accurately played a very large role in something that arguably had a greater impact on human evolution than anything else.

SciShow host Hank Green explains why keeping a calendar is more convoluted than we thought, and some ways people have tried to keep track of time in the past were incredibly confusing and even less reliable: