Pi Day is an annual celebration of the mathematical constant π (pi). Pi Day is on March 14th (3/14 in the month/day date format) as 3, 1, and 4 are the first three digits of π (3.14).
The earliest know official celebration of Pi Day was organised by Larry Shaw in 1988 at the San Francisco Exploratorium where he worked as a physicist, with staff and the public marching around a circular space and later eating fruit pies.
On March 12th 2009, th US House of Representatives recognised March 14th 2009 as National Pi Day.
Some observed the entire month of March 2014 (3/14) as ‘Pi Month.’ In the year 2015, Pi Day had special significance on 3/14/18 (mm/dd/yy date format) at 9:26:53 a.m and p.m as the date and time represented the first ten digits of π. Pi Day in 2016 was also significant because its mm/dd/yy (3/14/16) represents pi rounded to the first five digits.
People observe Pi Day in numerous ways including eating pie, throwing pies and discussing the significance of the number π.
Princeton, New Jersey, hosts many events in a combined celebration of Pi Day and Albert Einstein’s birthday, which is also March 14th. Einstein lived in Princeton for more than twenty years while working at the Institute for Advanced Study. In addition to pie eating and recitation contests, there is an annual Einstein look-alike contest.