Why is PI Day = 14 March?

PI is the mathematical constant describing the relation between the diameter of a circle and the circumference.

PI has an unlimited number of digits, and begins with 3,14159265.....

Note the first part of it: 3,14

While most of the world would write 14 March as 14.03 (DD.MM), the US date format is exactly opposite (MM.DD), so 14 March would be written 3.14.

Even though 14 March would only be written 3.14 in the US, it is celebrated all over the world as international PI Day.

Albert Einstien was born on this date in 1879.

 

PI Approximation

While PI has an unlimited number of decimals for maximum accuracy, a more inaccurate number is sometimes used in simple math to get close to the real PI: 22/7.

22/7 is only accurate down to 2nd decimal, yet it also has it's own day: The PI Approximation Day on 22/7.