March 14 is Pi day. No we are not talking about the Apple, Pumpkin and Pecan flavored "pies", but "Pi" the number: approxitmately 3.14159 or more exactly "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." Pi itself has an infinite decimal expansion; because it is an irrational number, its decimal expansion never ends and does not repeat. It has been calculated to 1.26 trillion digits. Learn more on Wikipedia.

There was a Pi Day celebration in San Francisco.

There is even a Pi song: