It's March 14th:  Pi Day! March 14th = 3/14 which is 3.14, Pi! It's also Albert Einstein's birthday BTW. For a refresher on Pi let's turn to our friends at PiDay.org:

Pi (Greek letter “π”) is the symbol used in mathematics to represent a constant — the ratio of the circumference of a circle to its diameter — which is approximately 3.14159.... As an irrational and transcendental number, it will continue infinitely without repetition or pattern.

Or, if you learn best through What Does the Fox say parodies check this out:

How about the Pi Song from Chris Hardwick and Mike Phirman?