# What Is Pi Day? Definition and Ways to Celebrate 2

### Question: What Is Pi Day? When Is It?

Answer: March 14 (03/14) is Pi Day, in honor of the number named pi. Pi is the ratio of a circle’s circumference to its diameter, which comes out to be 3.14159… (The calculation has been carried out past a trillion digits so far). Pi is an important mathematical constant, so a day was designated to honor it.

### When Was the First Pi Day?

Larry Shaw at the San Francisco Science Museum named the Exploratorium founded Pi Day in 1988. Originally, celebrations involved contests seeing who could recite the most digits of pi and eating pie. The United States House of Representative made Pi Day official in the US in 2009 (111 H. Res. 224). In 2019, UNESCO’s 40th General Conference named Pi Day as the International Day of Mathematics.

### How to Celebrate Pi Day

There are lots of ways to honor the number pi:

• Eat pie or pizza. Watch for great Pi Day deals!
• Make Pi Day cookies. Yes, there are even cookie cutter shaped like pi.
• Watch movies with a math theme or the word “pi” in the title. Try “Life of Pi” or “Pi”.
• Wear a Pi Day t-shirt. Some great Pi Day-themed shirts are also funny, like chicken pot pi (with a chicken in a flower pot and the letter pi), Pi-rates (a swashbuckling pi, complete with eyepatch and cutlass), and Octo-pi (octopus + pi).
• Run a Pi Day marathon. You can go 3.14 kilometers or miles.
• Memorize as many digits of pi as you can.
• Since Pi is an irrational number, you could simply be irrational all day.