March 14 is Pi Day. That's because pi, the ratio of the circumference to the diameter of a circle, starts with the digits 3.14159. So, March 14, at 1:59 p.m. (or a.m. if you're up) is the appropriate day and minute to celebrate pi. We should pay special attention to Pi Day in Indiana, because Indiana has a special place in the history of pi. Back in 1897, Dr. Edwin J.