Tau Day | State of the Tau 2026
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State of the Tau 2026
Happy Tau Day, everyone!
When I first proposed using the Greek letter $\tau$ (tau) for the circle constant in 2010, I never imagined it would still be going so strong 16 years later. But here we are on 2026-06-28, and the number $\tau = C/r = 6.28\ldots$ remains as relevant as ever. I’d especially like to express my gratitude to you, since Tau Day would be nothing without all the terrific tauists who’ve made it all the way to tau’s Sweet Sixteen.
And of course it’s twice as sweet with twice as much pie! 😋
Tau’s Sweet Sixteen
One of the most inspiring things about Tau Day is the sheer variety of different ways people celebrate it. In honor of tau’s Sweet Sixteen, here are 16 examples from last year:
Happy Tau Day!
Classic sine wave spaghetti project in praise of Tau 🙌✨
P.s. if I can get 40 more followers today I’ll have Tau thousand (a τ-sand) followers 🥰 tell your friends! pic.twitter.com/d48AaXtTaN<br>— Ayliean (@Ayliean) June 28, 2021
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... pic.twitter.com/KxPnt6SNVo<br>— Dave's Daily Doodle (@davesdailydoodl) June 28, 2025
🥧 Happy Tau Day (6.28)! Double the Pi, double the fun. #TauDay | #MathHumor | #MPSLearningInAction pic.twitter.com/itwXi5LVqD<br>— Mustang Public Schools (@MustangSchools) June 28, 2025
🎉 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 pic.twitter.com/e5GxHYDeyl<br>— Mathnasium (@Mathnasium) June 28, 2025
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. pic.twitter.com/nXe6ugsjr2<br>— SLMath (MSRI) (@mathmoves) June 27, 2025
#PiDay vs. #TauDay<br>3.14 = Einstein's birthday<br>6.28 = My daughter's birthday<br>I'm still on the fence.<br>— John Preskill (@preskill) March 14, 2025
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 🔢💬 pic.twitter.com/S0hVBigKdy<br>— MATHCOUNTS (@MATHCOUNTS) June 28, 2025
Get ready to circle around some math fun! Tau Day is coming up on June 28, where we celebrate the mighty τ (tau) instead of π. Twice the fun, twice the circle! 🎉 pic.twitter.com/GsyLyymduq<br>— Nerdy Talk (@NerdspotE) June 28, 2025
It’s Tau Day for those who celebrate it!! 🙌🎉
Tau is 2xPi = 6.28 pic.twitter.com/0bF9pbutIy<br>— Art Wong (@ArtWong128) June 28, 2025
happy Tau Day, y’all #tauday pic.twitter.com/T2xBpNvJ2G<br>— Yair Mau (@MauYair) June 28, 2025
Today is Tau Day (𝛕=6.28) pic.twitter.com/6YFbIzldcU<br>— Diver (@DeepDiverQ) June 28, 2025
Tau Day. https://t.co/Uss7aM8dHK pic.twitter.com/nwJ4qTlSZl<br>— jessica (@jessioa5) June 28, 2025
Happy Tau Day 06.28 pic.twitter.com/kyKlBNCbuI<br>— Daimion Kai Zafox 🌿🌼🌸 (@DaimionKaiZafox) June 28, 2025
🎉 It’s 6.28—time to celebrate the constant that goes the distance. Happy Tau Day to the scholars who never do things halfway! 🧠🚀 #AcademicExcellence #TauDay pic.twitter.com/e6l0pcu0Hd<br>— The Honor Society of Phi Kappa Phi (@phikappaphi) June 28, 2025
𝜏 vs. 𝜋<br>Tau vs. Pi<br>6.28 vs. 3.14
Today, these two mathematical constants face off in the ultimate nerdy showdown. For decades, Pi Day has reigned supreme—celebrated with pies, puns, and prestige. But today—June 28—tau steps into the ring. And it’s not just here to play. It’s… pic.twitter.com/ct1K1y1rnw<br>— Emerald Education (@edu_emerald) June 28, 2025
Tau 🙌🏽!! pic.twitter.com/lAVV5jgPXo<br>— Gautam Godse (@gautamgodse) June 29, 2025
Among many standouts, I’m especially pleased to see pioneering quantum information theorist John Preskill on the list above. (Technically, Preskill’s post was on Half Tau Day, but I’m going to count it.) Preskill probably wouldn’t remember this, but I actually had him for a physics course (Physics 136c) back when I was a graduate student at Caltech. He was also the Ph.D. advisor for my longtime friend Sumit Daftuar, who gets a separate shout-out in the acknowledgments of The Tau Manifesto, second only to “$\pi$ Is Wrong!” author Bob Palais.
Tau-pilling Claude, et al.
Speaking of Bob Palais, Bob sent me this...