Pi Day

Pi Day is an annual celebration of the mathematical constant π (pi). It is observed on March 14 because the date matches the first three digits of pi: 3, 1, and 4. This special day was founded in 1988 by Larry Shaw, an employee of the Exploratorium, a science museum in San Francisco.

People often celebrate Pi Day by eating pie and holding fun competitions to see who can recite pi the longest. In 2009, the United States House of Representatives officially supported Pi Day, showing how important it is for math and science. In 2019, UNESCO declared Pi Day as the International Day of Mathematics, making it a worldwide event.

There are also other days to celebrate pi! One is Pi Approximation Day on July 22, using the fraction 22/7 as an approximation of π. Another is on June 28, which represents the value of 2π or 𝜏 (tau). Pi Day helps people of all ages appreciate the beauty and importance of mathematics.

History

In 1988, Pi Day was first celebrated at the San Francisco Exploratorium by Larry Shaw, a physicist there. People walked around a circular space and enjoyed fruit pies. The museum still holds Pi Day events every year.

Later, in 2009, the U.S. House of Representatives passed a non-binding resolution to recognize March 14 as National Pi Day. Google also celebrated Pi Day with special images on its search page in 2010 and again in 2018 for the 30th anniversary. Some people even celebrated the whole month of March 2014 as "Pi Month" because the date, 3/14, matches pi. In 2015, March 14 was called "Super Pi Day" because the date, written as 3/14/15, showed the first five digits of pi.

Observance

Pi Day is celebrated on March 14 because the first three digits of the mathematical constant π (pi) are 3, 1, and 4. People often enjoy eating pie and sometimes throw pies in fun activities, playing on the similarity in sound between "pi" and "pie." Many pizza and pie restaurants offer special deals on this day, and schools may hold contests where students try to remember as many decimal places of pi as possible.

Some interesting traditions include the Massachusetts Institute of Technology, which has historically mailed or posted its application decisions for students on Pi Day. In Princeton, New Jersey, events combine Pi Day with the birthday of famous scientist Albert Einstein, including pie-eating contests and an Einstein look-alike contest. In 2024, a mathematician named Matt Parker and volunteers calculated many digits of pi by hand, showing the fun and challenge of working with this important number.

Alternative dates

Pi Day is most commonly celebrated on March 14, but some people choose other dates to honor the mathematical constant π (pi).

One such date is Pi Approximation Day, held on July 22. This date matches the fraction 22⁄7, an old and easy way to estimate pi. Another celebration is Tau Day on June 28, which honors the constant tau, equal to twice pi. Some people on this day like to eat twice as much pie! In some places, pi is also celebrated on November 10, because it is the 314th day of the year.