Yellow Pigs Day
annually on July 17th
Yellow Pigs Day is celebrated with things related to yellow pigs, but the main focus of the day is on celebrating the number 17. The day was created in the early 1960s by two Princeton math students, Michael Spivak and David Kelly, after they had been working with and listing the properties of the number 17. The days' name likely was a reference to David Kelly's collection of yellow pigs. The day's mascot became a yellow pig with 17 toes, 17 eyelashes, and 17 teeth. Since the early 1970s, Kelly has run the Hampshire College Summer Studies in Mathematics (HCSSiM), a summer high school math program for talented students, where a fun approach to doing math is emphasized. The day is celebrated there more than anywhere else, and many alumni from the program return to celebrate. Kelly traditionally gives a lecture on the number 17. The two biggest ways the day is celebrated, both there and by celebrants all around the world, is by the eating of yellow pig cake and the singing of yellow pig carols. The day is also marked with math-themed shirts with yellow pigs on them, the playing of ultimate frisbee, and the folding of origami yellow pigs, among other things.
How to Observe
Celebrate the day by learning about and working with the number 17. The sum of the first 4 prime numbers—2, 3, 5, and 7—is 17. Seventeen itself is a prime number. According to some studies, when people must pick a number between 1 and 20, they are more likely to choose 17 than any other number. Heptadecaphobia is the fear of the number 17. Today can be celebrated by eating a yellow cake that is shaped like a pig, or some yellow marzipan pigs. You may also make some yellow origami pigs, get some yellow pig plush toys, or play ultimate frisbee. One of the most important ways to celebrate the day is to sing yellow pig carols.