Pi Day - wikipedia Pi Day For National Pie Day, see American Pie Council § National Pie Day. Pi Day Larry Shaw, the organizer of the first Pi Day celebration at the Exploratorium in San Francisco. Significance 3, 1, and 4 are the three most significant figures of π Celebrations Pie eating, discussions about π Date March 14 Next time March 14, 2019 ( 2019 - 03 - 14 ) Frequency Annual Related to Pi Approximation Day Part of a series of articles on the mathematical constant π 3.14159 26535 89793 23846 26433... Uses Area of a circle Circumference Use in other formulae Properties Irrationality Transcendence Value Less than 22 / 7 Approximations Memorization People Archimedes Liu Hui Zu Chongzhi Aryabhata Madhava Ludolph van Ceulen Seki Takakazu Takebe Kenko William Jones John Machin William Shanks Srinivasa Ramanujan John Wrench Chudnovsky brothers Yasumasa Kanada History Chronology Book In culture Legislation Pi Day Related topics Squaring the circle Basel problem Six nines in π Other topics related to π Pi Day is an annual celebration of the mathematical constant π ( pi ). Pi Day is observed on March 14 ( 3 / 14 in the month / day format ) since 3, 1, and 4 are the first three significant digits of π. In 2009, the United States House of Representatives supported the designation of Pi Day. 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. Two Pi Day, also known as Tau Day, is lightly observed on June 28 ( 6 / 28 in the month / day format ). Contents 1 History 2 Observance 3 See also 4 References 5 External links History 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. 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. 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 π. Observance Pi Day has been observed in many ways, including eating pie, throwing pies and discussing the significance of the number π, due to a pun based on the words `` pi '' and `` pie '' being homophones in English ( / paɪ / ), and the coincidental circular nature of a pie. Massachusetts Institute of Technology 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 ''. June 28 is `` Two Pi Day '', also known as `` Tau Day ''. 2π, also known by the Greek letter tau ( τ ) 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, hosts numerous events in a combined celebration of Pi Day and Albert Einstein 's birthday, which is also March 14. 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. Pi Pie at Delft University Blackberry Pi Pie A grocery store selling pies for 3.14 dollars, Pi Day 2015 See also Mole Day Sequential time Square Root Day References ^ Jump up to : Landau, Elizabeth ( March 12, 2010 ). `` On Pi Day, one number ' reeks of mystery ' ''. CNN. Retrieved March 14, 2018. Jump up ^ Bellos, Alex ( March 14, 2015 ). `` Pi Day 2015 : a sweet treat for maths fans ''. theguardian.com. Retrieved March 14, 2016. Jump up ^ Program on Sveriges Radio -- Swedish national radio company Read March 14, 2015 ^ Jump up to : United States. Cong. House. Supporting the designation of Pi Day, and for other purposes. 111th Cong. Library of Congress. Jump up ^ `` Pi Approximation Day is celebrated today ''. Today In History. Verizon Foundation. Retrieved January 30, 2011. Jump up ^ Tau Day : Why you should eat twice the pie -- Light Years -- CNN.com Blogs Archived 12 January 2013 at the Wayback Machine. Jump up ^ Berton, Justin ( March 11, 2009 ). `` Any way you slice it, pi 's transcendental ''. San Francisco Chronicle. Retrieved March 18, 2011. Jump up ^ Borwein, Jonathan ( March 10, 2011 ). `` The infinite appeal of pi ''. Australian Broadcasting Corporation. Retrieved March 13, 2011. Jump up ^ Apollo, Adrian ( March 10, 2007 ). `` A place where learning pi is a piece of cake '' ( PDF ). The Fresno Bee. Jump up ^ `` Exploratorium 22nd Annual Pi Day ''. Exploratorium. Retrieved January 31, 2011. Jump up ^ McCullagh, Declan ( March 11, 2009 ). `` National Pi Day ? Congress makes it official ''. Politics and Law. CNET News. Retrieved March 14, 2009. Jump up ^ `` Pi Day ''. Google Doodles. Google. Retrieved October 9, 2012. Jump up ^ `` 30th Anniversary of Pi Day ! ''. www.google.com. Retrieved 2018 - 03 - 19. Jump up ^ Main, Douglas ( March 14, 2014 ). `` It 's Not Just Pi Day, It 's Pi Month ! ''. Popular Science. Retrieved July 22, 2014. Jump up ^ `` Pi Month Celebration & Circle of Discovery Award Presentation College of Computer, Mathematical, and Natural Sciences ''. Cmns.umd.edu. March 11, 2014. Retrieved July 22, 2014. Jump up ^ https://www.forbes.com/sites/ericmack/2015/03/14/happy-super-pi-day-heres-how-to-celebrate/ Jump up ^ Ro, Sam ( March 13, 2014 ). `` March 14, 2015 Will Be A Once - In - A-Century Thrill For Math Geeks ''. Business Insider. Retrieved March 13, 2014. Jump up ^ Smith, K.N. `` Wednesday 's Google Doodle Celebrates Pi Day ''. Jump up ^ McClan, Erin ( March 14, 2007 ). `` Pi fans meet March 14 ( 3.14, get it ? ) ''. msnbc.com. Retrieved January 24, 2008. Jump up ^ `` I have SMASHING news ! ''. MIT Admissions. Retrieved March 12, 2012. Jump up ^ McGann, Matt. `` Pi Day, Tau Time ''. MIT Admissions. Retrieved March 18, 2012. Jump up ^ `` Keep your eyes to the skies this Pi Day ''. MIT Admissions. Retrieved March 14, 2018. Jump up ^ `` It 's Pi Day today. But these people say we should refuse to celebrate it ''. The Independent. March 13, 2018. Retrieved March 14, 2018. Jump up ^ `` Pi Day Turns 25 : Why We Celebrate an Irrational Number ''. March 14, 2013. Retrieved March 14, 2018. Jump up ^ Bartholomew, Randyn Charles. `` Why Tau Trumps Pi ''. Scientific American. Jump up ^ Landau, Elizabeth. `` In case Pi Day was n't enough, it 's now ' Tau Day ' on the Internet ''. CNN. Jump up ^ `` Tau Day - Come Eat Twice the ( Pi ) e ''. ^ Jump up to : `` Princeton Pi Day & Einstein Birthday Party ''. Princeton Regional Convention and Visitors Bureau. Retrieved March 14, 2013. External links Wikimedia Commons has media related to Pi Day. Exploratorium 's Pi Day Web Site NPR provides a `` Pi Rap '' audiovideo Pi Day Professor Lesser 's Pi Day page Events commemorating achievements in the sciences Anniversary celebrations Alfred Russel Wallace centenary Darwin Centennial Celebration ( 1959 ) Regular holidays Ada Lovelace Day Darwin Day DNA Day Evolution Day Mole Day Pi Day Yuri 's Night Year long events First International Polar Year ( 1882 -- 1883 ) Second International Polar Year ( 1932 -- 1933 ) International Polar Year ( 2007 -- 2008 ) International Geophysical Year International Year of Planet Earth International Year of Astronomy International Year of Chemistry International Year of Crystallography International Year of Light International Space Year World Year of Physics 2005 Holidays, observances, and celebrations in the United States January New Year 's Day ( federal ) Martin Luther King Jr. Day ( federal ) Confederate Heroes Day ( TX ) Fred Korematsu Day ( CA, FL, HI, VA ) Idaho Human Rights Day ( ID ) Inauguration Day ( federal quadrennial, DC area ) Kansas Day ( KS ) Lee -- Jackson Day ( formerly Lee -- Jackson -- King Day ) ( VA ) Robert E. 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See also : Lists of holidays, Hallmark holidays, public holidays in the United States, New Jersey, New York, Puerto Rico and the United States Virgin Islands. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Pi_Day&oldid=842803495 '' Categories : 1988 establishments in California March observances July observances Observances about science Pi Recurring events established in 1988 Unofficial observances Hidden categories : Webarchive template wayback links Use mdy dates from March 2018 Infobox holiday fixed day Talk Contents About Wikipedia অসমীয়া Asturianu বাংলা Беларуская ( тарашкевіца ) ‎ Български Català Чӑвашла Čeština Cymraeg Dansk Deutsch Eesti Ελληνικά Español Esperanto فارسی Français 한국어 Հայերեն हिन्दी Hrvatski Bahasa Indonesia Íslenska Italiano עברית ಕನ್ನಡ ქართული Kiswahili Lietuvių Magyar Македонски മലയാളം Nederlands नेपाली 日本 語 Norsk Norsk nynorsk ଓଡ଼ିଆ Polski Português Română Русский Scots සිංහල Simple English Slovenčina Slovenščina کوردی Srpskohrvatski / српскохрватски Suomi Svenska தமிழ் తెలుగు ไทย Türkçe Українська Tiếng Việt 文言 粵語 中文 52 more Edit links This page was last edited on 24 May 2018, at 19 : 24. 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Question: when did the u.s. government recognize pi day as a holiday
Answer: 2009