Pi Approximation Day is held on July 22, or in the more common day/month date format as 22/7, which is an approximate value of π.

Pi Day is celebrated on March 14, or in the month/day date format as 3/14; since 3, 1 and 4 are the three most significant digits of π. March 14 is also the birthday of Albert Einstein so the two events are sometimes celebrated together.