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Pi Day (3.14) is celebrated on March 14th every year, following the American date system of Month-Day.
Pi is one of the most important mathematical constants, approximately equal to 3.14159. It represents the ratio of any circle's circumference to its diameter in Euclidean geometry, which is the same as the ratio of a circle's area to the square of its radius.
It is an irrational number, which means that it cannot be expressed as a fraction m/n, where m and n are integers.
The numerical value of p truncated to 50 decimal places is
3.14159 26535 89793 23846 26433 83279 50288 41971 69399 37510
Archimedes (287-212 BC) was the first to estimate pi rigorously. He realized that its magnitude can be bounded from below and above by inscribing circles in regular polygons and calculating the outer and inner polygons' respective perimeters.
The most digits calculated on a home PC is by Shigeru Kondo on his Xeon X5460 @3.16Ghz with 48GB RAM using Windows 2003 server x64. Kondo calculated 100,000,000,000 digits using the 64-bit version of Pagliarulo's QuickPi v4.5. It took just under 40 days beginning on January 16, 2008.
Latest record for digits on a supercomputer is 1,241,100,000,000 digits as of November 2002 by Yasumasa Kanada's lab at The University of Tokyo.
Sources: *.wiki*, mathematicianspictures.com
