There are tons of iconic national holidays to celebrate this month: National Pancake Day, National Earmuff Day, National Open An Umbrella Indoors Day. But nothing comes close to Pi day. Because while these other national holidays come to an end, Pi Day actually doesn’t come to an end, because though Pi technically isn't infinite, it does, in a sense, never fully end.

Pi, formally known as π in the world of mathematics, is the ratio of the circumference of a circle and the diameter of a circle. Circles are infinite since the line of a circle never ends. In simpler terms, for the circumference, if you take your finger and trace a circle, you will never reach a breaking point. This means circles, and evidently the circumference of a circle, is infinite. The diameter is the length across.

So does that mean the number is infinite as well? Technically no, though no one has ever been able to find a true end to the number. It's actually considered an "irrational" number, because it keeps going in a way that we can't quite calculate.

Pi dates back to 250 BCE by a Greek mathematician Archimedes, who used polygons to determine the circumference. He proved that the number is somewhere between 3.1408 and 3.1429. Basically by that point Archimedes determined that people would indulge on tons of apple pie on Mar. 14, even if days weren’t determined by a calendar year quite yet.

As time went on, more mathematicians continued to get closer and closer to the final number. In 150 ACE the number was determined to be around 3.146, then in 1630 the number expanded to 39 digits. Now the number is reported to have 2.7 trillion digits, the most recent recorded number was found in 2010.

To conclude, as famously described by Hazel Grace Lancaster in *The Fault In Our Stars, *“some infinities are bigger than other infinities.” And in this case, the world still has no idea how far this infinity could go.

Nevertheless, there is one infinity we can count on ending during pie day... which is how many slices of apple pie you can stuff in your stomach on Mar. 14.