Pythagorean Theorem Day or Pythagoras Theorem Day is celebrated when the sum of the squares of the first two digits in a date equals the square of the last digit in the date.
The holiday gets its name from Pythagoras' Theorem, which defines the relationship between the sides of a right triangle or a right-angled triangle – a triangle where one angle is at 90 degrees. According to the Theorem, in a right triangle, the square of the hypotenuse (the longest side of the triangle) is equal to the sum of the square of the other two sides. The Theorem is named after Greek mathematician and philosopher, Pythagoras, who is thought to have formulated the proof for it.
The holiday is also sometimes called Right Triangle Day or Pythagoras Day.
Upcoming Pythagorean Theorem Days
Whether you write your dates in the mm/dd/yy format or the dd/mm/yy format, here are some dates you can celebrate this unique mathematical holiday in the near future.
August 15, 2017 (8/15/17 or 15/8/17): 8² + 15² = 17²
December 16, 2020 (12/16/20 or 16/12/20): 12² + 16² = 20²
July 24, 2025 (7/24/25 or 24/7/25): 7² + 24² = 25²
Here are some ways you can make the most of this uncommon holiday:
Learn more about the Pythagoras Theorem and its real life applications.
Celebrate the day by eating foods that are cut in right angle triangles. Make a pizza or bake a cake or cookies in the shape of a right triangle. Too much work for you? Why not make triangular Rice Krispie treats?