Happy National Pi Day! Pi Day is celebrated each year on March 14, a date that coincides with the numerical value of π, used in mathematics to represent the ratio of the circumference of a circle to its diameter, which is approximately 3.14. In reality, π is an irrational and transcendental number, according to piday.org, which means it goes on infinitely beyond its decimal point. National Pi Day is most appropriately celebrated with a slice of pie, sweet or savory, that can range from fruit pie to deep dish pizza pie. The possibilities are nearly as endless as π itself, but 10 states across the country have made the selection a bit easier by naming certain varieties of pie among their official state foods.