March 14, 15:09:02. This date and time correspond to the first six decimal places of pi (π), the infinitely long number that begins ‘3.141592…’. It was created to commemorate ‘Pi Day (π-day)’. Pi ...

Pi, a mathematical constant denoted by the Greek letter π, is the ratio of a circle's circumference C to its diameter d: π = C/d. The circumference of a circle is, in turn, equal to 2πr, where r is ...