Pi is a mathematical constant that is the ratio of a circle's circumference to its diameter, and it is also one of the most revered mathematical constants in the known world.[1] Pi Day was first officially celebrated on a large scale in 1988 at the San Francisco Exploratorium.[2] Since then, Pi Day has been celebrated by millions of students and math-lovers each year. The holiday is celebrated on 14th March, since 3 (the month of March) 1 and 4 (the 14th day) are the first three and most well-known digits in the decimal form of pi. Though you can observe this fun little holiday however you choose, there are a few pi day celebrations that are popular and guarantee a good time for everyone!