Pi Day

Pi Day is an annual celebration of the mathematical constant π (pi). Pi Day is observed on March 14 (3/14 in the month/day date format) since 3, 1, and 4 are the first three significant digits of π. In 2009, the United States House of Representatives supported the designation of Pi Day.

Pi Approximation Day is observed on July 22 (22/7 in the day/month date format), since the fraction ²²⁄₇ is a common approximation of π, which is accurate to two decimal places and dates from Archimedes.

https://en.wikipedia.org/wiki/Pi_Day