Tuesday, March 14 is Pi Day, a day to celebrate the mathematical constant 3.14159265 (and on and on and on). Pi is the symbol used to represent the ratio of a circle’s circumference to its diameter. 

The date — 3/14 — is also the day that restaurant chains offer up deals on pies and pizzas. Whether you’re celebrating for the mathematical constant, a slice of pepperoni pizza or both, take advantage of these deals on Tuesday, March 14.  More Here