It's March 14* of the year '15, or 3-14-15 — the first five digits of the number pi. It's a confluence that won't happen again for a hundred years. Math geeks are excited.
"Pi has certain fascination, due to the fact that its digits appear to be unpredictable," says Po-Shen Loh, a math professor at Carnegie Melon University and U.S. coach for the International Mathematical Olympiad. "It's usually the first irrational number that students encounter."