Pi Day is celebrated every March 14, because the date written the American way, 3/14, matches the first three digits of π. This countdown goes one step further and ticks down to 1:59 a.m. Eastern Time, the moment when the date and clock together read 3/14 1:59, or 3.14159. The next Pi Day is Sunday, March 14, 2027.
How a museum party became an international day
The first Pi Day celebration was organized in 1988 by physicist Larry Shaw at the Exploratorium, the hands-on science museum in San Francisco. Staff and visitors marched around a circular space and then ate fruit pies. The idea spread through schools and math departments, and on March 12, 2009, the US House of Representatives passed a non-binding resolution (H.Res. 224) recognizing March 14 as National Pi Day.
In November 2019, UNESCO’s General Conference proclaimed March 14 the International Day of Mathematics, first celebrated in 2020. So outside the US you may hear both names for the same date. Fittingly, March 14 is also Albert Einstein’s birthday (1879), and physicist Stephen Hawking died on March 14, 2018.
Why 1:59?
π begins 3.14159, so the extra digits 1, 5 and 9 become the time. Some people mark the moment at 1:59 a.m. and others wait for 1:59 p.m., which is much more practical for classrooms and offices. A few go further and celebrate at 1:59:26, adding the next two digits. If you need an afternoon version, you can create your own countdown on this site with any time you like.
Ways to celebrate
- Eat pie, obviously: fruit pie, pot pie, pizza pie; many bakeries and pizza chains run Pi Day specials, often priced at $3.14.
- Hold a digit-recitation contest: see who in your class or office can recite the most digits of π from memory.
- Measure circles: wrap a string around plates, cans and bike wheels, divide by the diameter and watch the answer creep toward 3.14.
- Write a “pi-ku”: a short poem with lines of 3, 1 and 4 syllables.
- Try a pi puzzle: NASA’s Jet Propulsion Laboratory has published a Pi Day Challenge of space-themed math problems for students in past years.
Pi Day traditions you may not know
MIT has long timed its admissions decisions around Pi Day. Since 2012 it has released them online on Pi Day at 6:28 p.m., a nod to tau (τ = 2π ≈ 6.28). Fans of tau even have their own day on June 28, joking that it means twice the pie. Pi Approximation Day on July 22 celebrates 22/7, the fraction Archimedes used to bound π.
Plan ahead
If you are a teacher, March 14 often falls close to spring break, so check your school calendar early. Share this countdown link with your class or put it on the board in full-screen mode; watching the seconds roll toward 1:59 is a surprisingly good way to get students curious about the number itself.