The Chicago Tribune (3/14, Ford) reports that "Monday is Pi Day," in honor of "the number that expresses the ratio of a circle's circumference to its diameter" and "starts with 3.14159. Thus, March 14, or 3/14, for Pi Day." The celebration started in San Francisco in 1989 and "has spread around the world, and math teachers, students and other self-proclaimed math fans amused or intrigued by pi celebrate the number." The Tribune points out that "one highlight of many Pi Day events is a competitive recitation of the numerous digits of pi, which modern computers have calculated to a trillion decimal places." Chicago's Morgan Park Academy has a "record" of 312 digits, and one Walter Payton College Prep student who now attends Yale University "remembered a mind-blowing 500 digits."