Has no one told you the Earth rotates one extra day every year?

You’ve probably heard that Earth takes 365 days to orbit the Sun. So far, so good.

You might also have heard that Earth completes one rotation every day, which makes intuitive sense because the Sun rises and sets every 24 hours, and that’s what a “day” is, right?

But here’s the kicker…

Earth actually rotates 366 times per year.

Wait, what?

Yep. That means Earth spins around its axis one more time than there are days in a year. If your brain just short-circuited, you’re not alone.

This weird little fact feels paradoxical — like something a smug astronomer might drop into a bar conversation just to stir up confusion. But it’s not a trick. It’s a very real and very understandable outcome of how we define “a day.”

Let’s untangle it.

The astronomical fine print

To understand what’s going on, we need to talk about two kinds of “days.”

A sidereal day is how long it takes Earth to complete one full rotation relative to the fixed stars. It’s about 23 hours, 56 minutes.

A solar day is how long it takes Earth to rotate so that the Sun appears in the…