Corrected entry: The outdoor night scenes are illuminated by high-pressure sodium vapor streetlights, which did not come into use until the mid-1980s. Streetlights of the 1970s used mercury vapor lamps, which give a quite different bluish-white light.
Corrected entry: When Darlene is parking her car in a "more quiet place", you can see the tire marks of where she is going to park, from previous takes.
Correction: She's parking in a public park, right in a parking stall that may have been used by any nmber of previous vehicles, not necessarily hers. There are other vehicles coming in going during the scene, which suggests the park was a fairly popular place for a make out point.
Corrected entry: In the scene the morning after the taxi driver murder, the detectives were driving on a San Francisco street where a 'bus lane only' diamond was visible/painted on the street. These did not exist then.
Correction: The first bus lane was actually made in 1939, and were highly used by the 60's, during the zodiac killings.
Corrected entry: Toward the end of the movie there is the scene where Robert Graysmith goes to Arthur Leigh Allen's work place and stares at him for a long time. In this scene you can see Leigh's name tag, but his name is spelled "Lee" not "Leigh". This could be considered not a mistake, however in an earlier scene we see case files with his name specifically spelled "Leigh".
Correction: Case files and a name tag come from completely different sources. Entirely possible for the name tag to be spelled incorrectly, and just not corrected by Arthur yet.
Corrected entry: Some of the computers shown in the scenes at the newspaper, set in the 1970's, are a newer style than what was available at the time. They look like they are from the 1980's.
Correction: This needs to be more specific. Which computers? Which scenes?
Corrected entry: When Robert Graysmith goes to Arthur Leigh Allen's work place The text on the screen reads "1983". The calendar in the shop behind Leigh shows the date "February 1980".
Correction: Not necessarily a mistake. I still have last year's calendar hanging in my kitchen. Some of us are just lazy.
Seems like an error to me. Being lazy to take down an old calendar is understandable, but the movie text states the date is December 1983 and the calendar is showing February 1980. Leaving an old calendar up for almost 4 years in public view seems unlikely, and suddenly stopping even using that calendar in February seems equally unlikely. I'm inclined to think that the scene was shot with all props in place, and date text for those final scenes was added towards the end of editing and the calendar was overlooked at that point.
Correction: I don't know about San Francisco but I remember that in New York City sodium vapor lights were being installed in the late 60s - early 70s.