Tau Day

6/28 is #TauDay, a celebration of the true circle constant. Founded with The Tau Manifesto by @mhartl, which proposed using the name τ (tau) for C/r = 6.28…

[Tau Day @TauDay]

Happy Tau Day, everyone! 2025 marks the 15th anniversary of Tau Day and The Tau Manifesto. Please enjoy this year’s State of the Tau update with some of the happenings since Tau Day last year.
https://t.co/bqh5CyBPph

[Wil @WilPollock]

Happy half @TauDay !! Today @MIT releases its regular decisions, usually at 06:28 PM in homage to my mate Michael Hartl.
Congrats to those admitted!
To those not: you will find your home.
#goEngineers
#goBeavers

[Tau Day @TauDay]

@egprentice Weird. Sorry for the trouble!

[Tau Day @TauDay]

Happy Tau Day, everyone! 2025 marks the 15th anniversary of Tau Day and The Tau Manifesto. Please enjoy this year’s State of the Tau update with some of the happenings since Tau Day last year.
https://t.co/bqh5CyBPph

[Tau Day @TauDay]

@egprentice Hmm, I definitely wouldn’t expect it to take that long. According to the website, it should ship within a week or so of ordering. Maybe you could reach out to Teespring customer support to see what’s going on?

[Tau Day @TauDay]

@mrburkemath Lots of people care! https://t.co/nr6MoHiAz7

[Tau Day @TauDay]

Some people might say the answer is π, but on today of all days it behooves us to write the answer as arctan(∞) − arctan(−∞) = ¼τ + ¼τ = ½τ. 🤓

[The Math Flow @TheMathFlow]

Solve the improper integral.

[Tobias Brandt (@tobiasbrandt.bsky.social) @T0bias_Brandt]

Happy #TauDay folks! Let's continue the good fight.

Tau Day | State of the Tau https://t.co/IG3coRDWla

[Mathnasium @Mathnasium]

🎉 Happy Tau Day! 🎉

Today, we celebrate the beauty of mathematics and the constant “tau,” which is double the value of pi! Check out our latest blog article to explore more: 👉 https://t.co/KQKA3FRtLH.

#Mathnasium #TauDay #MathIsFun

[Dave's Daily Doodle @davesdailydoodl]

Happy Tau Day Everyone! I used a pipette to drop India inks onto watercolour paper for this #TauDay picture. I'm interested to see how it dries later...

[Scottsbluff Math Team @SBMathClub]

Happy Tau Day! #iykyk

[Tau Day @TauDay]

Took a sec to realize this is a picture of Tau Day birthday boy @elonmusk, who turns 54 today.

[jessica @jessioa5]

Tau Day.

[Tau Day @TauDay]

Don’t cry—lots of people are celebrating Tau Day! https://t.co/j9S1A7yx73

[Yair Mau @MauYair]

happy Tau Day, y’all
#tauday

[MATHCOUNTS @MATHCOUNTS]

June 28 is special because today there are not only one, but TWO mathematical reasons to celebrate! Today is Perfect Number Day and Tau Day! If you know what connects those concepts to today’s date, be the first to leave your explanation in the comments 🔢💬

[SLMath (MSRI) @mathmoves]

Happy @TauDay! Join our puzzle contest featuring double the pi(e) with two Tau-themed puzzles by Prof. Peter Winkler, and support mathematics research and public outreach:

[Tau Day @TauDay]

Do you remember when you joined X? I do! #MyXAnniversary #TauDay

[SLMath (MSRI) @mathmoves]

Double the π, double the fun: this weekend we celebrate #TauDay 6.28, which means it's time for our annual puzzle contest! We welcome your support and invite all to join the contest by July 13, with this year's guest puzzlemaster, Peter Winkler: https://t.co/w5s8S1gJWw.

[Tau Day @TauDay]

SLMath (@mathmoves) is planning to run a Tau Day promotion again this year, and we’re looking for someone special to step up with a $6,280 matching gift. Interested in helping to inspire even more support for SLMath’s exceptional programs? Reach out to [email protected]. Thanks!

[Tau Day @TauDay]

Happy Half Tau Day, everyone! https://t.co/vhXtuILiLa

[Michael Hartl @mhartl]

2π = “around a circle”—yet another argument for τ