Pi Day is next celebrated on March 14th 2020 all over the world. Why March 14th? Well, that's because the Greek letter Pi (π) is used in mathematics to represent a constant - originally this was the ratio of a circle's circumference to its diameter, but it has various definitions now and is used in many mathematics and physics formulas.
Pi is most commonly shown as being 3.14159 but this is just an approximate value. It's an irrational number, and its decimal representation never ends.
Take a look at what one million digits of pi looks like!
