Factual error: The story takes place during spring of 1976 but Marty's parents drive a 1979 station wagon.
Other mistake: It is stated at the beginning of the film that the events that take place start in the spring of 1976, and span over the summer. The Climax, and final scene of the movie, take place on Halloween night. In the scene directly after Milt Sturmfuller was killed, the gas station attendant is seen reading about the slaying in the local newspaper. The date on the paper is Friday September 8, 1980.
Factual error: When Marty is on the covered bridge, after running from the pastor, he hears a tractor running. He starts yelling for Mr. Zimmerman, who is driving the tractor, and Mr. Zimmerman stops the tractor and walks to the covered bridge. It would have been nearly impossible for Mr. Zimmerman to hear Marty yelling for him over the noise of the tractor.