Tau Day is a mathematical holiday. Even schoolchildren know a constant mathematical value – the number π (pi), which expresses the ratio of the circumference to the diameter of a circle and is approximately 3.14. The number π has its own holiday, with the date associated with the value of pi – March 14 (3.14). However, mathematics professor Robert Palais from the University of Utah thought there was a more precise way to express the relationship between a circle and its radius.

## History

In 2001, Palais published the article “π is Wrong” in the mathematical journal The Mathematical Intelligencer. In it, he proposed using a new constant instead of π – the circle constant 2π (6.28). In 2010, Palais’ idea was supported by Michael Hart, who received a bachelor’s degree in physics from Harvard and a Ph.D. from the University of California. Hart proposed designating the constant proposed by Palais with the letter tau, published the Tau Manifesto, and founded Tau Day. The date of the holiday is also associated with the value of the number tau and is on the 28th day of the sixth month of the year.

## Interesting Facts

Michael Hart’s The Tau Manifesto has been translated into seven languages. Its author claims that Tau Day is today by thousands of mathematical “nerds” around the world.

## How to Take Part

Are you fond of mathematics and interesting discoveries in this area? You can celebrate Tau Day in many ways.

- On Pi Day, people usually eat pie. Tau supporters argue you can safely eat a cake twice as large on Tau Day – after all, the value of tau is twice that of pi! You can also celebrate the holiday with any food that resembles a circle, such as a huge pizza!
- This is a great day to have math games and competitions with kids or discuss the latest math news with friends.
- Post information about this unusual holiday on your social networks. Let the holiday help people learn more about mathematics.

## When is Tau Day in 2024?

Tau Day is observed on June 28 each year.

### Observations

Weekday |
Month |
Day |
Year |

Friday | June | 28 | 2024 |

Saturday | June | 28 | 2025 |

Sunday | June | 28 | 2026 |

Monday | June | 28 | 2027 |

Wednesday | June | 28 | 2028 |

Thursday | June | 28 | 2029 |