Pi Day and also Pi Approximation Day, are two days held as holidays, in which to celebrate a mathematical constant, pi. The date March 14th, is also Albert Einstein’s birthday, so often the events are sometimes celebrated together.

There are even jokes for Pi day (although somewhat corny), such as Q: What do you get when you take the sun and divide it’s circumference by it’s diameter? A: Pi in the sky and by.

Pi, which is also a Greek letter, is used as the symbol for the ratio of the circumference of a circle to it’s diameter. And Pi is a much celebrated day especially for maths enthusiasts around the world on March 14th. Pi=3.1415926535…

And now with the use of computers, it has been calculated to over a trillion digits past the decimal. Which means that Pi is an irrational number, while also being transcendental, so it will continue infinitely without repeating.

First used by William Jones in 1706, the symbol for pi, was popular also after being taken on by the Leonhard Euler a Swiss mathematician in 1737.