Happy Pi (π) Day ✍️ Pi Day is an annual celebration of the mathematical constant π (pi), observed on March 14 because the date (3/14) matches the first three digits of π. The celebration was first organized in 1988 by Larry Shaw at the Exploratorium. Since then, it has become a popular event among mathematicians, scientists, teachers, and students. Pi Day celebrations often include eating pie, reciting the digits of π, and organizing math-related activities. In 2009, the United States House of Representatives officially recognized the day. Later, in 2019, the UNESCO declared March 14 as the International Day of Mathematics, giving Pi Day a global scientific significance.