Pi Day is celebrated on March 14th (3/14) around the world. Pi (Greek letter “”) is the symbol used in mathematics to represent a constant — the ratio of the circumference of a circle to its diameter — which is approximately 3.14159. Pi has been calculated to over one trillion digits beyond its decimal point.

March 14 is Pi Day. It is a day to celebrate the mathematical constant pi (π) and to eat lots of pie. Celebrated in countries that follow the month/day (m/dd) date format, because the digits in the date, March 14 or 3/14, are the first three digits of π (3.14), Pi Day was founded by Physicist Larry Shaw in 1988.