Pi Day!

Why are so many people excited about today, 3/14/15? It's "Pi Day," so called because the number pi rounded to the nearest ten-thousandth is 3.1415. If you want to round off to the nearest billionth, pi is 3.141592654, so if you trust your clock enough, you can get especially rapturous over Pi Day at 9:26 and 54 seconds! (I'm posting this after the morning 9:26, but you can still celebrate the evening one... the last 3/14/15 9:26 of the century.)