A day for celebrating Pi – the ratio of a circle’s circumference to its diameter.
Pi Day is celebrated in a variety of ways. Parties or other observances may be held by mathematics departments in educational institutions. Harvard’s Math department, for instance, has a pi recitation contest as well as a pie eating contest. Mathematics or science clubs might gather to consider the role that the number Ï€ has played in their lives and to imagine the world without Ï€. During such an event, pi celebrants may approximate Ï€, devise alternative values for Ï€, eat pie, play piÃ±ata, drink PiÃ±a Colada, eat pizza (which itself is called pizza pie), listen to the song “Pi” by Kate Bush, watch Pi, or recite Pi. The song 867-5309/Jenny is sometimes sung, replacing the digits with the first several digits of pi.*
*source: wikipedia – Pi Day