From San Francisco to Shanghai, in museums, universities, classrooms, and in private homes around the world, people are celebrating the 24th Annual Pi Day, an international holiday born at San Francisco’s Exploratorium, on Wednesday, March 14, according to press.exploratorium.edu.

The number is Pi (π), 3.1415926535…ad infinitum. It’s the number you get when you divide the circumference of a circle by its diameter. It cannot be expressed as a fraction.

It’s also the date and time of festivities at the Exploratorium and a special occasion to celebrate some of the Exploratorium’s quirky scientific traditions before the museum moves to Pier 15 in 2013. Most importantly, 3 p.m. the brass Pi Shrine will be ceremoniously removed in preparation for its reinstallation at museum’s new location.

This international “geek” holiday was founded in 1988 by Exploratorium’s physicist and Prince of Pi Larry Shaw.