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

### by Michael Hartl

Tau Day is a celebration of the circle constant $\tau = C/r =$ $6.283185\ldots$ Founded in 2010 with the publication of The Tau Manifesto by Michael Hartl, Tau Day takes place annually on June 28 (6/28 in the American calendar system).

The Tau Manifesto proposed using the Greek letter $\tau$ (tau) to represent the true circle constant and ignited the Tauist Movement that continues to gain strength with each passing year. To learn more, 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 $\tau$.