What on Earth is Tau Day? Aren't you thinking about Pi Day... and aren't you about three months too late?" you might be asking.
Nope. I'm thinking of of Tau Day, a celebration of Tau (τ).
"That's all well and good, Dave, but what's Tau and why is it so special?"
Glad you asked! For those who aren't familiar, I'll let Dr. Kevin Houston, mathematician at the University of Leeds do the talking:
If you couldn't watch the video: Circles are defined by their radii, not their diameters. As such, Pi (π) as a the universal circle constant carries along with it some fundamental flaws. Instead, it has been proposed to replace π with a more logical circle constant, τ, where τ is the ratio of a circle's circumference to it's radius: τ = C/r = 6.2831... In other words, τ = 2π.
If you really want to learn more about the subject, including a variety of mathematical arguments for the use of τ instead of π, check out the Tau Manifesto by Michael Hartl. It's a real good lunchtime read, especially if you feel like revisiting your days in calculus class.
The beauty part of Tau Day? You get two eat twice as much pi(e) as you would on Pi Day.