Pi Day is an annual celebration of the mathematical constant pi π in the US. Pi Day is observed on March 14 (3/14) since 3, 1, and 4 are the first three significant digits of π.
The earliest known official or large-scale celebration of Pi Day was organized by Larry Shaw in 1988 at the San Francisco Exploratorium.
Pi Day can be celebrated in a number of ways, most commonly by eating pies, discussing its significance, holding math quizzes etc.
Some ideas and resources to celebrate Pi Day in English: