Every year Pi day is celebrated on March 14th around the world.

Pi (Greek letter “π”) is the symbol used in mathematics to represent a constant — the ratio of the circumference of a circle to its diameter — which is approximately 3.14159.

Pi Day started 28 years ago at San Francisco's Exploratorium. Physicist Larry Shaw, who worked in the electronics group at the museum, started celebrating pi on March 14, 1988, primarily with museum staffers. The tradition has grown to embrace math enthusiasts from all walks of life.