If you were to measure the circumference of a circle, then divide it by its diameter, you will always get the same result (depending on how accurately you measure, of course). That number is π (pi) and it is approximately 3.1415926…
On March 14 1988, physicist Larry Shaw organized the first Pi Day celebration at the Exploratorium in San Francisco. Staff and patrons marched around in a circle, then ate pie. Simple and elegant.
Pi Day is celebrated around the world every year but 2015 is special; it is Ultimate Pi Day. Once every century, the numbers representing the date (3/14/15) are the same as the first 5 digits of pi (3.1415).
If you want to take the celebration to its extreme you can celebrate Ultimate Pi Moment which occurs at 9:26.53 (3.141592353).
Some people mark the occasion by participating in a 3.14 mile (5.05334 km) run and probably enjoy some pie after.
Personally, I’m going to celebrate Pi Day by wearing my favorite t-shirt and maybe eating some pie because there’s never a bad reason to have pie.
Here are some cookbooks that will help with the celebration.
175 Best Mini Pie Recipes by Julie Anne Hession
Crazy About Pies: Irresistible Pies for Every Sweet Occasion by Krystina Castella
Pie School: Lessons in Fruit, Flour and Butter by Kate Lebo
as found on http://torontopubliclibrary.typepad.com/bookbuzz/2015/03/have-some-pie-on-pi-day.html