Pi Approximation Day is held on July 22 in the day/month date format because it is the approximate value of π (22/7 = 3.14).
Whereas, Pi dayis the unofficial holiday that celebrates the mathematical constant pi (π) on March 14 in the month/day date format because the digits in this date correspond with the first three digits of π (3.14). It has become an international observance that is celebrated live and online and also celebrates Albert Einstein’s birthday.
What is Pi (π)?
Pi (π) is the mathematical constant that has been known for almost 4000 years. Its value is the ratio of any circle’s circumference to its diameter in Euclidean space or the ratio of a circle’s area to the square of its radius. The value of pi is approximately equal to 3.14159265, but it is an irrational number and its decimal representation never ends or repeats.
The lower case Greek letter π is used because it is the first letter of the Greek work περίμετρος (perimeter), which probably refers to its use in the formula perimeter divided by diameter equals the constant for all circles. The concept of π has become the most common ground between mathematicians and non-mathematicians.