March 14 is Pi Day. It is a day to celebrate the mathematical constant pi (π) and to eat lots of pie.
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.28 (6/28 in the month/day format). - Wikipedia
How to Celebrate?
Pi is a homophone of pie - the 2 words are pronounced similarly but are spelled differently and mean different things. Celebrate Pi Day by having lots and lots of pie.
Have a pie baking contest. Ask participants to bake pi shaped pies. Combine it with a pie eating competition.
Have a pi recitation contest. Anyone who can recite the most digits of the constant gets to take home a pie. - Fun Holiday Calendar