# Happy Pi Day! Pi Day is an annual celebration of the mathematical constant π (pi). Pi Day is observed on March 14 (3/14 in the month/day format) since 3, 1, and 4 are the first three significant digits of π. In 2009, the United States House of Representatives supported the designation of Pi Day.

Pi Approximation Day is observed on July 22 (22/7 in the day/month format), since the fraction ​227 is a common approximation of π, which is accurate to two decimal places and dates from Archimedes.[5

https://en.wikipedia.org/wiki/Pi_Day

The number π (/p/) is a mathematical constant. Originally defined as the ratio of a circle‘s circumference to its diameter, it now has various equivalent definitions and appears in many formulas in all areas of mathematics and physics. It is approximately equal to 3.14159. It has been represented by the Greek letter “π” since the mid-18th century, though it is also sometimes spelled out as “pi“. It is also called Archimedes’ constant. https://en.wikipedia.org/wiki/Pi