<P> Pi Approximation Day is observed on July 22 (22 / 7 in the day / month format), since the fraction ​ ⁄ is a common approximation of π, which is accurate to two decimal places and dates from Archimedes . </P> <P> Two Pi Day, also known as Tau Day, is lightly observed on June 28 (6 / 28 in the month / day format). </P> <P> In 1988, the earliest known official or large - scale celebration of Pi Day was organized by Larry Shaw at the San Francisco Exploratorium, where Shaw worked as a physicist, with staff and public marching around one of its circular spaces, then consuming fruit pies . The Exploratorium continues to hold Pi Day celebrations . </P> <P> On March 12, 2009, the U.S. House of Representatives passed a non-binding resolution (111 H. Res. 224), recognizing March 14, 2009 as National Pi Day . For Pi Day 2010, Google presented a Google Doodle celebrating the holiday, with the word Google laid over images of circles and pi symbols; and for the 30th anniversary in 2018, it was a Dominique Ansel pie with the circumference divided by its diameter . </P>

Where did the numbers for pi day and pi minute come from