While there’s a “food holiday” for just about everything you love to eat, it turns out there are actually two separate days every year when people come together to celebrate pie: National Pie Day on January 23 and Pi Day on March 14. As you can imagine, it’s easy to confuse the two occasions when there’s, say, free pie and pizza involved, but Pi Day is about much more than stuffing your face with the flaky, fruit-filled desserts.

Now would be a great time to grab a generous slice of apple pie (and maybe some ice cream on top) before we dig into what makes Pi Day special. Learning makes you hungry, right?

Pi Day is a celebration of the mathematical constant, π (pi), or 3.14159265359. You might recognize this number if you’ve taken a geometry class! As you can see, the date is literally the first three major numbers, when you write March 14 in a numerical format, like 3/14.

That’s right: Pi Day is about math, but thankfully, someone made it fun with pies. Best of all, a lot of people tend to celebrate the occasion with pizza, too. We think that aspect makes Pi Day *better* than National Pie Day.

Pi has been calculated to over one trillion digits beyond its decimal point. As an irrational and transcendental number, it will continue infinitely without repetition or pattern. While only a handful of digits are needed for typical calculations, Pi’s infinite nature makes it a fun challenge to memorize, and to computationally calculate more and more digits.

Various ancient civilizations calculated approximations of pi, including the Egyptians and Babylonians; There’s even a reference to the dimensions of a circle in the Bible!

But the first calculation of pi as 3.14 is attributed to Greek mathematician Archimedes, who lived in the third century B.C. It was also independently determined by Chinese mathematician Zu Chongzhi (429–501), who computed pi to six decimal places. Mathematicians adopted the symbol π for the expression in the 18th century; Welsh mathematics teacher William Jones is often credited with the first use of the symbol in 1706.

In basic mathematics, Pi is used to find area and circumference of a circle. You might not use it yourself every day, but Pi is used in most calculations for building and construction, quantum physics, communications, music theory, medical procedures, air travel, and space flight, to name a few.

As you can see, Pi day is pretty awesome: Not just because of the pizzas and the actual pies, but because of the infinite possibilities the constant itself represents through it’s immeasurable uses and endless trail of digits.

How will you celebrate Pi day?

*Fun Fact! Pi Day is also Albert Einstein’s birthday! Who would have thought?*