See also: 1985A
Timeline 4 or Timeline C, sometimes called the "Biffhorrific timeline", was an alternate history created when "old" (78) Biff Tannen, from 2015, gave Grays Sports Almanac to his younger self, 18 year old Biff Tannen, on November 12, 1955. Doc Brown, Marty McFly, Jennifer Parker, and Doc's dog Einstein returned from 2015 to a different-looking 1985 than the one they had departed. Doc described the alternate reality as 1985A, and soon discovered that the history of that timeline had started diverging at some point before 1958. Eventually, it was determined (by asking Biff) that the skewing of the timeline had begun on November 12, 1955, and Doc and Marty traveled to that day, arriving a few hours before Old Biff's visit was to begin.
Before Doc and Marty's intervention, however, Timeline 4 was changing the course of historical events from 1955 onward.
Behind the scenes
- As with the other timelines, some of the alternate reality can be witnessed directly, while other aspects of it can be inferred from newspaper headlines and dialogue. In effect, Timeline 4 is happening in the final hour of Back to the Future Part II from the moment that old Biff is seen collapsing (as 2015 alters to 2015A), until the moment that Marty's burning of the almanac causes objects from 1985A to return to what was normal for Timeline 2.