Read the State of the Tau 2021 update!

# No, really, pi is wrong… The Tau Manifesto

### by Michael Hartl

Tau Day is an annual celebration of the circle constant $\tau = 6.283185\ldots$, which takes place every June 28 (6/28 in the American calendar system). To learn more about what $\tau$ (tau) is and why it’s important, read The Tau Manifesto, or watch one of the tau videos below.

To get all the latest updates on tau, read the State of the Tau update, and join the official tau email list.

## Tau Videos

Michael is ashamed to admit that he knows $\pi$ to 50 decimal places—approximately 48 more than Matt Groening. To atone for this, he has memorized 52 decimal places of $\tau$.