The Pi Approximation Day is celebrated on the 22nd of July each year. Why? 22/7!
Pi (π) is the ratio of the circumference of a circle to its diameter and one can get its value accurate to two decimal places by dividing 22 by 7. Pi’s approximate value of 22/7 was probably proposed by Archimedes.
Using π, the sixteenth letter of the Greek alphabet, as the symbol for pi was first proposed by William Oughtred, an English mathematician and minister. Oughtred is also credited to have been the first to use ‘x’ as a symbol for multiplication. However, it was the great German mathematician, Leonhard Euler, who popularised the use of π.
The actual Pi Day is celebrated on 14th of March which also happens to be the birthday of the great physicist Albert Einstein.