Tau Day is observed worldwide every June 28, celebrating the mathematical constant tau (τ), which is approximately equal to 6.28. This day was inspired by Pi Day, which has been celebrated on March 14 since the late 1980s, and was first organized by physicist Larry Shaw at the San Francisco Exploratorium. The concept of Tau Day emerged from proposals by mathematicians Robert Palais and Michael Hartl, who suggested using tau to represent the number of radians in a full turn, contrasting with the more commonly known pi (π). While not widely adopted in the mathematical community, a small group of enthusiasts celebrates Tau Day, often humorously suggesting that participants should eat twice the amount of pie, as both "pi" and "pie" sound alike and pies are circular.