When Is National Pi Day 2025 Date. Find out the dates, history and traditions of national pi day Pi day is observed every year on march 14 to commemorate the mathematical constant of pi.

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 pi. Pi day is observed every year on march 14 to commemorate the mathematical constant of pi.