No, really, pi is wrong: The Tau Manifesto

Michael Hartl · Tau Day

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’s introduction of $\tau$ (tau) as the “true circle constant” has had a significant impact on geek culture, including changing the

time of day

MIT announces its admissions decisions, being featured in the official

Google calculator

, and being supported by a large number of computer programming languages (including Microsoft .NET, Java, Rust, and Python).

Including the English-language original, The Tau Manifesto is currently available in eight different languages. Its associated holiday,

Tau Day

, has been

featured in The Wall Street Journal

and is celebrated annually on

6/28

by thousands of math enthusiasts around the world.

To get all the latest updates on tau, read the

State of the Tau update

, and

join the official Tau Email List

.