This semiregular mathematical holiday celebrates 1/3, a simple fraction that appears on the calendar once every seven years when the third day of the year falls on a Thursday.
Though it is, by itself, a finite number, it also represents eternity in the form of 1/3 = 0.33333333...
Celebrations
Thirdsday is observed on January 3 (1/3) in the U.S., but for most of the world the date 1/3 refers to March 1. Consequently, it is celebrated on different days in different cultures.
Thirdsday cannot be celebrated halfway, but thirdway. Split a pizza or cake with two friends. Drink a third of a six-pack.
Discovered by mathematics blogger Jim Propp, Thirdsday recognizes the importance of thirds in our daily lives.
"Thirdsday is better than Pi Day for a whole bunch of reasons.," he explains. "For one thing, 1/3 turns up a lot more than Pi and is much more useful in most people’s daily lives. Also, 1/3 doesn’t snootily insist on having its own special symbol, and its decimal expansion is a lot easier to remember."
He suggests doing things by thirds on Thirdsday and offers a trick borrowed from math educator James Tanton for trisecting a pile of candies:
If you’ve got a pile of candies, split it into a smaller pile and a larger pile (don’t worry about the exact sizes).
Now take the larger pile and split it as evenly as you can by eye into two equal halves.
Take one of those halves and combine it with the previously smaller pile.
Keep doing this over and over: take the larger pile, split it in half, and merge one of those halves with the other pile. The more you do this, the closer you get to a two-to-one split of the candy