National Yellow Pig Day

Celebrated on 07/17/2026

Quick Fact

National Yellow Pig Day, celebrated on July 17th, is a whimsical holiday that originated among mathematicians at Princeton University. The day honors a fictional yellow pig with 17 toes, and enthusiasts often decorate with yellow pig imagery and even eat yellow-colored foods.

Origins and Establishment of National Yellow Pig Day

National Yellow Pig Day was created in the early 1960s by two Princeton University mathematicians, David Kelly and Michael Spivak. The holiday emerged from a playful conversation about the number 17, which led to the invention of a mythical yellow pig with exactly 17 toes. The date July 17 (7/17) was chosen to honor this unique number.

Evolution and Modern Commemoration

Initially celebrated among a small circle of mathematicians, the holiday has since spread through academic communities and online platforms. Today, enthusiasts mark the day by sharing yellow pig memes, creating yellow pig art, and hosting small gatherings. Some traditions include eating yellow foods like lemon bars or banana pudding, and wearing yellow clothing. The holiday remains a lighthearted celebration of mathematical curiosity and whimsy.

Facts & General Observations

• The number 17 is considered a 'Fermat prime' (a prime number of the form 2^(2^n)+1), adding mathematical significance to the holiday.
• National Yellow Pig Day is not officially recognized by any government or major institution, but it has a dedicated following on social media.
• In some celebrations, participants create 'yellow pig' piñatas filled with yellow candies.

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