Pi Day: π Day

3/14 is the day to celebrate the ratio of the circumference of a circle to its diameter.
And here is pi:

The first time a day was dedicated to pi was on March 14, 1989 at the Exploratorium, a museum of science, art and human perception in San Francisco. Pi Day is celebrated by performing pi-related activities; some serious and some less so, such as creating pi puns; baking, throwing and eating pies; and singing pi songs.