Pi Day

Pi Day is a holiday that celebrates the mathematical constant, Pi (∏). It is celebrated on March 14 because the first three digits of Pi are 3.14 -- although true enthusiasts mark the actual time of the holiday as 1:59 p.m., also known as the Pi Minute, or 1:59:26 p.m., the Pi Second. (While it is possible to estimate with great precision the moment at which the holiday occurs, it is impossible exactly to define.) Pi Jokes are traditionally told on Pi Day. March 14 is also, coincidentally, the birthday of Albert Einstein. On March 11, 2009, the House of Representatives passed a resolution making March 14th officially National Pi Day.CNET: National Pi Day?... (March 11, 2009)

The earliest approximations of pi appear from the Babylonians over 4000 years ago. According to an artifact dating back to approximately 1700 B.C., they measured it as 3.125. Another artifact, an Egyptian papyrus document, showed that the Egyptians used 3.1605 as a constant to calculate the area of circles as far back at 1650 B.C. The ancient mathematician Archimedes calculated the value of pi by using the Pythagorean Theorem. He determined that pi was between 3 1/7 and 3 10/71.ExplOratorium: A Brief History of π

Despite this longstanding knowledge of the constant, a universal symbol was not used to describe it until the 1700s. William Jones was the first to appropriate the use of the symbol "π" in 1706. Leonhard Euler began using the symbol in 1737 after which it became popularized.ExplOratorium: A Brief History of π