One way Caltech celebrates Pi Day is with a schoolwide pie eating event for the undergrads! Every year on March 14 at 1:59 AM (in honor of the first 6 digits of pi), a huge long table with five different types of pie is laid out. This year Pi Day was during finals week, so students took a break from studying and exams to eat free pie. Departments and classes also celebrate Pi Day - for example, the CMS department had pie at noon for everyone in the department in the CS building, and one of my classes celebrated with Uncle Tetsu cheesecake (not pie, but close enough :P). How did you celebrate Pi Day?