Pi Day is an annual celebration of the mathematical constant (pi). Pi Day is observed on March 14 (3/14 in the ''month/day''

format Format may refer to: Printing and visual media * Text formatting, the typesetting of text elements * Paper formats, or paper size standards * Newspaper format, the size of the paper page Computing * File format, particular way that informati ...

) since 3, 1, and 4 are the first three

significant figures Significant figures (also known as the significant digits, ''precision'' or ''resolution'') of a number in positional notation are digits in the number that are reliable and necessary to indicate the quantity of something. If a number expre ...

of . It was founded in 1988 by Larry Shaw, an employee of the

San Francisco San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...

, California science museum, the Exploratorium. Celebrations often involve eating pie or holding pi recitation competitions. In 2009, the

United States House of Representatives The United States House of Representatives, often referred to as the House of Representatives, the U.S. House, or simply the House, is the lower chamber of the United States Congress, with the Senate being the upper chamber. Together the ...

supported the designation of Pi Day.United States. Cong. House. Supporting the designation of Pi Day, and for other purposes. 111th Cong
Library of Congress

UNESCO The United Nations Educational, Scientific and Cultural Organization is a specialized agency of the United Nations (UN) aimed at promoting world peace and security through international cooperation in education, arts, sciences and culture. I ...

's 40th General Conference designated Pi Day as the

International Day of Mathematics The International Day of Mathematics is 14 March. It is also known as the Pi Day, because the mathematical constant (pi) can be rounded down to 3.14. UNESCO's 40th General Conference decided Pi Day as the International Day of Mathematics in N ...

in November 2019. Alternative dates for the holiday include July 2222 July in the ''day/month'' format (22/7, an approximation of ) and June 28 (6.28, an approximation of 2 or tau).

History

In 1988, the earliest known official or large-scale celebration of Pi Day was organized by Larry Shaw at the

San Francisco Exploratorium The Exploratorium is a museum of science, technology, and arts in San Francisco, California. Characterized as "a mad scientist's penny arcade, a scientific funhouse, and an experimental laboratory all rolled into one", the participatory natur ...

, where Shaw worked as a

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate ca ...

, with staff and public marching around one of its circular spaces, then consuming fruit pies. The Exploratorium continues to hold Pi Day celebrations. 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 A Google Doodle is a special, temporary alteration of the logo on Google's homepages intended to commemorate holidays, events, achievements, and notable historical figures. The first Google Doodle honored the 1998 edition of the long-running ...

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 In geometry, the circumference (from Latin ''circumferens'', meaning "carrying around") is the perimeter of a circle or ellipse. That is, the circumference would be the arc length of the circle, as if it were opened up and straightened out t ...

divided by its

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...

. The entire month of March 2014 (3/14) was observed by some as "Pi Month". In the year 2015, March 14 was celebrated as "Super Pi Day". It had special significance, as the date is written as 3/14/15 in month/day/year format. At 9:26:53, the date and time together represented the first 10 digits of , and later that second Pi Instant represented all of 's digits.

Observance

Pi Day has been observed in many ways, including eating pie, throwing pies and discussing the significance of the number , due to a pun based on the words "pi" and "pie" being

homophone A homophone () is a word that is pronounced the same (to varying extent) as another word but differs in meaning. A ''homophone'' may also differ in spelling. The two words may be spelled the same, for example ''rose'' (flower) and ''rose'' (pa ...

s in English (), and the coincidental circular shape of many pies. Many

pizza Pizza (, ) is a dish of Italian origin consisting of a usually round, flat base of leavened wheat-based dough topped with tomatoes, cheese, and often various other ingredients (such as various types of sausage, anchovies, mushrooms, ...

and pie restaurants offer discounts, deals, and free products on Pi Day. Also, some schools hold competitions as to which student can recall pi to the highest number of decimal places.

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private Land-grant university, land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern t ...

has often mailed its application decision letters to prospective students for delivery on Pi Day. Starting in 2012, MIT has announced it will post those decisions (privately) online on Pi Day at exactly 6:28 pm, which they have called "Tau Time", to honor the rival numbers pi and tau equally. In 2015, the regular decisions were put online at 9:26 am, following that year's "pi minute", and in 2020, regular decisions were released at 1:59 pm, making the first six digits of pi. June 28 is "Two Pi Day", also known as "Tau Day". 2, also known by the Greek letter tau () is a common multiple in mathematical formulae. Some have argued that τ is the more fundamental constant, and that Tau Day should be celebrated instead. Celebrations of this date jokingly suggest eating "twice the pie".

Princeton, New Jersey Princeton is a municipality with a borough form of government in Mercer County, in the U.S. state of New Jersey. It was established on January 1, 2013, through the consolidation of the Borough of Princeton and Princeton Township, both of whi ...

, hosts numerous events in a combined celebration of Pi Day and

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...

's birthday, which is also March 14. Einstein lived in Princeton for more than twenty years while working at the

Institute for Advanced Study The Institute for Advanced Study (IAS), located in Princeton, New Jersey, in the United States, is an independent center for theoretical research and intellectual inquiry. It has served as the academic home of internationally preeminent scholar ...

. In addition to pie eating and recitation contests, there is an annual Einstein look-alike contest. File:Pi pie2.jpg, Pi Pie at Delft University File:Pi day sale.jpg, A grocery store selling pies for $3.14 on Pi Day File:Cremepiday.png, Creme pie in celebration of Pi day showing the greek letter and the first digits of Pi.

Alternative dates

Pi Day is most frequently observed on March 14, but related celebrations have been held on alternative dates. Pi Approximation Day is observed on July 22 (22/7 in the ''day/month'' format), since the

fraction A fraction (from la, fractus, "broken") represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight ...

is a common approximation of , which is accurate to two decimal places and dates from

Archimedes Archimedes of Syracuse (;; ) was a Greek mathematician, physicist, engineer, astronomer, and inventor from the ancient city of Syracuse in Sicily. Although few details of his life are known, he is regarded as one of the leading scienti ...

. Two Pi Day, also known as Tau Day for the mathematical constant tau, which is approximated as 6.28, is observed on June 28 (6/28 in the ''month/day'' format). Pi Approximation Day is also observed on the 10th of November since it is the 314th day of the year.

Notes

References

External links