Tau (τ) is the 19th letter of the Greek alphabet. Some mathematicians have proposed its use over pi (π) as a circle constant. It is defined as the ratio of the circumference of a circle to the radius, rather than the diameter.
In Greek numerals, Tau has a value of 300. However, with τ being equal to 2π, its value approximated to 6.283185.
This translates to 6.28 or the 28th of June which is celebrated as Tau Day.
FYI, Pi Day falls on the 14th of March (3.14, which also happens to be Albert Einstein’s birthday) and is celebrated by eating pies! Apparently, on Tau Day one has to eat twice the amount of pie!
