 There exist enough clues in all three movies to reconstruct the  travels of the DeLorean precisely (to within a few minutes at worst,  except 2015 Biffs arrival in 1955 and Docs personal travels).  There are a few interesting things to note: Not counting the time  Doc traveled by himself, the DeLorean spent nearly 71 years (on its  own time scale) from its first time travel to its destruction. By  the time Marty made his ultimate return to 1985, he was approx. 14  days, 3 hours, and 27 minutes older than he should have been;  Jennifer, on the other hand, is 7 hours and 26 minutes younger than  she should have been. Another interesting conclusion is a point of  contention. There are two theories, one of which drops the last  item. On November 12, 1955, between the time Biff arrived (or 6 am,  whichever came later) and 6:38 pm (the time he left), there were  four DeLoreans present in Hill Valley (ordered from its point of  view): (1) The instance when Marty was trapped in 1955 in the  original movie, (2) the instance when Biff came to 1955 to give  himself the almanac, (3) the instance when Marty and Doc came back  to 1955 to take the almanac back, and (4) the instance when it was  waiting in the abandoned mine. Those who do not agree with (4) argue  that according to the "ripple effect" timeline as presented in the  films, there wouldnt be a DeLorean hidden by Doc in the mine until  later that evening, when the lightning blast would accidentally send  Doc back to 1885, thereby altering the timeline. It is *entirely  true* that *we* do not ever witness a moment in the films where all  four instances coexist, but the text "ordered from its point of  view" above should hint at a solution. Once the DeLorean is in 1885,  consider what it would detect (if it were in a position to witness  the comings and goings of its former selves): over 70 years of  peace, then (1) arrives, then (2) and (3) arrive in some order; (2)  then leaves at 6:38, (3) leaves around 10 pm, and (1) leaves at  10:04. (4) itself leaves soon after that. If we grant that all three  of those instances (1