【Watch Sukeban Deka the Movie 2: Counter】

It's a big day for number nerds.

The Watch Sukeban Deka the Movie 2: Counterdate Nov. 23 – really 11/23, since formatting makes a difference here – marks Fibonacci Day, a time when people on the internet take a moment to remember high school math class. The day owes its name to a 13th century Italian mathematician who is popularly known as Fibonacci (though that's not his name).

You probably know him better as a math lesson. The Fibonacci sequence is a series of numbers in which each one is the sum of the two numbers that came before it. So Nov. 23, or 1-1-2-3, is a simple example that the calendar circles back to every year: 1+1=2, 1+2=3. (The next number in the sequence is 5. You get the picture.)

The Fibonacci sequence pops up in everything from music to computer science. There's evidence that its use predates the Italian mathematician for whom it's named. The numbers even pop up in natural science, to help explain the patterns we find there.

It's such a recurring presence in the world, in fact, that a quarterly publication exists just to talk about that (a fact I just learned today). If you're still confused, browsing through social media on Fibonacci Day is honestly a great way to get a handle on things.

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