 The clock in the clock tower started running at 8:00 p.m. on  September 5, 1885. The date is provided by the caption on the  photograph Doc gives Marty at the end of the movie. The lightning  strikes the clock tower at 10:04 p.m. on November 12, 1955. This  means that the clock tower operated for exactly 70 years, 2 months,  7 days, 2 hours, and 4 minutes.