SatJul 17

Yellow Pig Day – July 17, 2021

We celebrate the number 17 with Yellow Pig Day on July 17. Although this might sound like a pork-appreciation day, it’s actually a day to enjoy the wonders of mathematics, and particularly the special properties of the number 17. Whether you’re a math rookie or a world-leading professor, we have all the mind-boggling facts and history of Yellow Pig Day right here, along with some super-smart suggestions of how to make it a great day!

History of Yellow Pig Day

In the 1960s, students Michael Spivak and David Kelly were studying math at Princeton. Together, they spent a lot of time considering the qualities of the number 17 and became obsessed with its incredible combination of simplicity and complexity that was recurrent in the mathematics they were using and developing.

Their obsession grew into a desire to celebrate the number 17 with its own special day, and they created a mascot for their event in the form of a yellow pig. But they morphed their pig into a beast with 17 teeth, 17 toes — 17 everything! — to encapsulate their passion for the number 17.

From its small beginnings, Yellow Pig Day has become a huge hit in the academic calendar, with students and teachers alike coming together to celebrate this special number, as well as math in general. Classes sing yellow pig carols, share cake, and play games based around the number 17. Some people even create origami yellow pigs and yellow pig T-shirts to wear with pride.

Both of its founders still work in the field of mathematics. Kelly continues to be involved in the organization of the holiday each year, commemorating the day with food, songs, and a reunion. His obsession with the number 17 is still going strong, and he even gives a special lecture on the subject every summer. He founded the Hampshire College Summer Studies in Mathematics (HCSSiM), a six-week program for mathematically talented high school students, designed to inspire and encourage them in the general field of mathematics, though it also probably includes the number 17 somewhere!

Yellow Pig Day timeline

1940s
Birth of the Founders

Yellow Pig Day founders Michael Spivak and David Kelly are born.

1960s
Yellow Pig Day Invented

Michael Spivak and David Kelly create Yellow Pig Day following their obsession with the number 17.

1971
Math-Students Inspired

David Kelly founds the Hampshire College Summer Studies in Mathematics (HCSSiM).

1977
Carols Composed

The carol ‘The March of the Yellow Pig’ is composed to commemorate the day and is still sung on college campuses in celebration.

Yellow Pig Day FAQs

Why is this such a popular day?

Despite its small origins, Yellow Pig Day gained a cult following amongst mathematicians and it’s become a fantastic moment to celebrate math.

When can I celebrate real pigs?

October 4 is when we celebrate World Animal Day, and is the ideal time to pay tribute to other kinds of pigs.

Why did they use a yellow pig?

It’s unclear why the founders chose a yellow pig as their mascot, but we’re glad they did as it makes Yellow Pig Day such a fun way to celebrate math!

Yellow Pig Day Activities

  1. Collect 17 things

    Celebrate the number 17 by collecting 17 things from your favorite category — flowers, books, chocolates, the choice is yours!

  2. Draw a yellow pig

    Create your own Yellow Pig Day mascot for the day, and make sure to include the number 17 somehow for extra credit!

  3. Research the number 17

    The number 17 has some fascinating properties, as well as a resonance throughout history. You’ll be surprised by what you find!

5 Intriguing Facts About The Number 17

  1. It’s a prime number

    As a prime number, it’s a number that is greater than 1 that cannot be formed by multiplying two smaller numbers.

  2. It’s the sum of the first four prime numbers

    If you add the first four prime numbers together (2+3+5+7) you’ll get the number 17. That’s one of the things Yellow Pig Day founders loved so much about it!

  3. It’s democratic

    The 17th Amendment of the United States Constitution grants citizens the right to a democratic vote on their chosen senators.

  4. It’s a sporting record

    In 1993 the Pittsburgh Penguins achieved the longest winning streak in NHL history with 17 wins.

  5. It’s poetic

    The popular poetic form, the haiku, is structured using 17 syllables, in three lines of 5, 7, and 5 syllables.

Why We Love Yellow Pig Day

  1. Math is useful!

    From simple arithmetic to complex algebra, we use math in our everyday lives, often without even realizing it.

  2. It makes math fun

    When things get complicated, it can be easy to switch off from math. But Yellow Pig Day reminds us that math can be fun and informative — a winning combination!

  3. It’s an excuse to geek out

    When you’re passionate about something, you can make it exciting for other people, just like Yellow Pig Day founders did with the number 17. What things can you geek out on to inspire others?

Yellow Pig Day dates

YearDateDay
2021July 17Saturday
2022July 17Sunday
2023July 17Monday
2024July 17Wednesday
2025July 17Thursday

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