A little reason to celebrate
Tau Day
Hobby · Fun · June 28
Tau Day is about tau, the circle constant equal to two times pi, which compares a circle's circumference to its radius.
Tau Day falls on Monday, June 28, 2027. That is 244 days away.
Tau is a number for circles. Divide the distance around any circle by its radius and you get the same answer every time, about 6.28. Mathematicians write it with the Greek letter tau, and it equals exactly two times pi.
The case people make for tau is about angles. In radians, one full turn around a circle is tau. A half turn is half of tau, a quarter turn is a quarter of tau, and so on. Fractions of the circle line up with fractions of the number, which some find tidier than counting in multiples of pi. Fans of pi have their own arguments, and the two camps tend to trade them in good humor.
Most of the people who mark the day are math teachers, students and hobbyists who like a friendly debate. Some draw circles and measure them with string to see the constant appear. Others memorize a few digits, sketch the unit circle with tau labels, or bake two pies on the reasoning that tau is twice pi.
You do not need any special tools to try it. A jar lid, a piece of string and a ruler will do. Wrap the string around the lid, measure it, then divide by the distance from the center to the edge. Your answer will wobble a little depending on how careful you are, but it should land somewhere near six and a quarter.
The digits after 6.28 keep going forever without repeating, just like pi's.
Ways to celebrate
- Measure a jar lid with string and divide by its radius.
- Relabel a unit circle sketch using fractions of tau.
- Memorize the first few digits of tau.
- Share the half turn and quarter turn idea with a friend.
- Bake two pies and split them with neighbors.
Dates
| Year | Date |
|---|---|
| 2026 | Sunday, June 28 |
| 2027 | Monday, June 28 |
| 2028 | Wednesday, June 28 |
| 2029 | Thursday, June 28 |
| 2030 | Friday, June 28 |
Also on June 28
Categories: Hobby daysFun days