Pi Day

Pi Day
Larry Shaw, the organizer of the first Pi Day celebration at the Exploratorium in San Francisco
Significance3, 1, and 4 are the three most significant figures of π in its decimal representation.
CelebrationsPie eating, discussions about π[1]
DateMarch 14
Next timeMarch 14, 2020 (2020-03-14)
First time1988
Related toPi Approximation Day

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.[2][3] In 2009, the United States House of Representatives supported the designation of Pi Day.[4]

Pi Approximation Day is observed on July 22 (22/7 in the day/month format), since the fraction227 is a common π, which is accurate to two decimal places and dates from Archimedes.[5]

Two Pi Day, also known as Tau Day, is lightly observed on June 28 (6/28 in the month/day format).[6]


In 1988, the earliest known official or large-scale celebration of Pi Day was organized by Larry Shaw at the San Francisco Exploratorium,[7] where Shaw worked as a physicist,[8] with staff and public marching around one of its circular spaces, then consuming fruit pies.[9] The Exploratorium continues to hold Pi Day celebrations.[10]

On March 12, 2009, the U.S. House of Representatives passed a non-binding resolution (111 H. Res. 224),[4] recognizing March 14, 2009 as National Pi Day.[11] For Pi Day 2010, Google presented a Google Doodle celebrating the holiday, with the word Google laid over images of circles and pi symbols;[12] and for the 30th anniversary in 2018, it was a Dominique Ansel [fr] pie with the circumference divided by its diameter.[13]

The entire month of March 2014 (3/14) was observed by some as "Pi Month".[14][15] In the year 2015, March 14 was celebrated as "Super Pi Day".[16] 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.[17]

Other Languages
العربية: يوم ط
অসমীয়া: পাই দিৱস
asturianu: Día de π
বাংলা: পাই দিবস
беларуская (тарашкевіца)‎: Дзень Пі
български: Денят Пи
català: Dia Pi
čeština: Den pí
dansk: Pi-dag
Deutsch: Pi-Tag
eesti: Pii päev
Ελληνικά: Ημέρα του πι
español: Día de π
Esperanto: Pi-tago
فارسی: روز پی
français: Journée de pi
한국어: 파이의 날
հայերեն: Պի թվի օր
हिन्दी: पाई दिवस
hrvatski: Dan broja pi
Bahasa Indonesia: Hari Pi
íslenska: Π dagur
עברית: יום פאי
ಕನ್ನಡ: ಪೈ ದಿನ
ქართული: პის დღე
Kiswahili: Siku ya Pi
lietuvių: Pi diena
македонски: Ден на бројот пи
മലയാളം: പൈ ദിനം
Nederlands: Pi-dag
नेपाली: पाई दिवस
日本語: 円周率の日
norsk: Pi-dagen
norsk nynorsk: Pi-dagen
ଓଡ଼ିଆ: ପାଇ ଦିବସ
português: Dia do Pi
română: Ziua pi
русский: День числа пи
Scots: Pi Day
සිංහල: පයි දිනය
Simple English: Pi Day
slovenčina: Deň pí
slovenščina: Dan pi
کوردی: ڕۆژی پای
srpskohrvatski / српскохрватски: Dan broja π
svenska: Pi-dagen
தமிழ்: பை நாள்
తెలుగు: పై డే
Türkçe: Pi Günü
українська: День пі
Tiếng Việt: Ngày số pi
文言: 圓周率日
粵語: 圓周率日
中文: 圓周率日