In Back to the Future II, Marty and Doc go back to 1955 to get the sports almanac from Biff to save the future while trying to avoid their younger selves. When they succeed they burn it while the storm is brewing. Marty 1 goes back to 1985, then Doc 2 goes to 1885 and Marty knows by a letter, then goes to the Doc of 1955 after Marty 1 goes back to 1985 and the Doc faints.
So I'm confused. When does the lighting hit the clock tower so Marty 1 goes back to 1985 while Marty 2 burns the almanac and learns Doc is in 1885?