After completing Back To The Future - The Game, I decided to look at the Back To The Future wiki, aka Futurepedia. Why? I wanted to see what the timeline would be like.
I was surprised while reading it that there are eight different timelines throughout the movie trilogy. Each timeline began whenever the time machine went back to the past. Any leaps into the future wouldn't affect the current timeline. I'm curious how many timelines there would now be if the Back To The Future - The Game episodes were considered canon. But it seems from the wiki that these weren't considered canon at all, which is a shame because it's a good game.
The timelines are a lot of fun to read if you're into the Back To The Future series.
Timeline 1 is pretty straightforward. This is the original, unaltered timeline. In this timeline, Biff becomes George's boss and continues bullying him.
Timeline 2 is the timeline brought into existence by Marty's accidental time journey into 1955. This timeline exists at the end of the first movie before Doc takes Marty and Jennifer into 2015. In this timeline, George becomes an author, and Biff becomes a car detailer.
Timeline 3 is the timeline Doc brings into existence by travelling to 1985 to seek Marty and Jennifer's help. In this timeline, the fate of the McFly children ought to have been greatly improved. Unfortunately, "Old" Biff's stealing the DeLorean and travelling back to 1955 retroactively changes this timeline's events and brings Timeline 4 into existence instead. Biff quickly returns the DeLorean to 2015 undetected (before any past alterations have occurred), and Doc, Marty, and Jennifer depart moments before it fades away. It is implied that Doc would bring Marty and Jennifer back to 1985 after the future excursion because their future selves still exist and are appropriately aged in 2015.
Timeline 4 is the timeline Old Biff brings into existence in 1955 by arriving from 2015 in the stolen DeLorean, almanac in hand. It is replaced with a virtually identical Timeline 5 on October 26th, 1985, when Doc, Marty, Einstein and Jennifer arrive from 2015 and observe the damage Biff has accomplished.
Timeline 5 is the alternate timeline brought into existence when Marty, Doc, Jennifer and Einstein return from 2015. This is referred to by Doc as 1985A, which is depicted in BTTF Part II. The key difference between this timeline and Timeline 4 is the simultaneous presence of two Martys (his doppelganger overseas at boarding school), two Docs (his doppelganger committed to a mental institution and unable to invent the time machine) and the alternate Einstein and Jennifer, the latter who is still unconscious from what she has witnessed in 2015 (their 1985A doppelgangers, if they have any, are never seen or mentioned).
Timeline 6 is the key timeline brought into existence when Doc and Marty arrive in 1955 to relieve Biff of his newly acquired almanac from the future, thus preventing Timeline 4 and Timeline 5 from coming into existence, but without disturbing Timeline 2 as Marty has previously accomplished. This timeline is depicted in the "1955" part of Back to the Future Part II. For clarification, this timeline can be considered a "patched" version of Timeline 2, with double Docs and Martys. It bears noting that at some point during this one-day period, three instances of Doc's DeLorean are present in Hill Valley simultaneously.
Timeline 7 is the timeline Doc and Marty exist in, separated by seven decades, at the end of Back to the Future Part II and the beginning of Part III (i.e., before Marty's trip back to 1885). It is a timeline in which Doc lives in 1885, without Marty, for only eight months and almost seven days. As it seems the careful Doc's presence has little impact on history (until 1955 when his DeLorean is unearthed), this timeline is nearly identical to Timeline 2 with Timeline 6. Because of Doc's unintended trip to 1885, on November 12th, 1955, in this timeline, four DeLorean time machines exist simultaneously because this is a timeline where a DeLorean has been stored in a mine for more than 70 years. Even as 1955 Doc is planning to send DeLorean "A" back to the future; 2015 Biff brings DeLorean "B" with an almanac inside, and 1985 Doc and Marty bring DeLorean "C" to retrieve the almanac -- there is DeLorean "D" inside the Delgado Mine.
Timeline 8 is the timeline that comes into existence when Marty arrives in 1885 to try to prevent the events that lead to Doc's death in Timeline 7 at the hands of Buford Tannen. It is this timeline that Doc and Marty appear for most of Back to the Future Part III. It is also the final timeline depicted in the trilogy, as the DeLorean will no longer travel backwards in time. Since Marty chooses not to race Needles upon his return to 1985, the future is changed again, and the alternate futures Doc and Marty have experienced in Timeline 2 and Timeline 3 are erased by this timeline. Note: Two DeLoreans exist in this timeline for five days in 1885, from September 2nd, when Marty arrived, until September 7th, when he departed for 1985.
If you're interested in reading about all the timelines in greater detail, then check out the Back To The Future timeline.
I think what I'll have to do at some point is continue the timelines as best as I can in my blog to include the games and any changes they would have possibly made to the future if they were considered canon, which I don't think a lot of people will. But it could be fun to try out.