Pi Day observed globally on March 14

Key facts

• Pi Day is celebrated annually on March 14 to honour the mathematical constant Pi (π) and the birth of physicist Albert Einstein.
• Pi represents the ratio of a circle’s circumference to its diameter, which is approximately 3.14 regardless of the circle's size.
• The first Pi Day was celebrated in 1988 by physicist Larry Shaw at the Exploratorium in San Francisco.
• The United States House of Representatives officially recognized March 14 as Pi Day in 2009.
• The United Nations Educational, Scientific and Cultural Organization (UNESCO) declared March 14 as the International Day of Mathematics in 2019.
• The symbol π was popularized by mathematician Leonhard Euler in 1737, while the first known calculations were made by the ancient Greek mathematician Archimedes.
• The Massachusetts Institute of Technology (MIT) traditionally releases undergraduate admission decisions on Pi Day at 6:28 p.m. Eastern Time, a reference to Tau Time.
• Buffon’s Needle is a probability experiment devised by French mathematician Georges-Louis Leclerc, Comte de Buffon, to estimate the value of Pi.