- Saturday, November 12
- 6:00 a.m. Doc and Marty arrive from 1985 in Timeline 10. Doc advises Marty that Biff's initial acquisition of the almanac must not be interfered with, so that the elderly Biff will return the time machine to 2015 thinking he’s succeeded.
- Later that same morning. The elderly Biff arrives in 1955 with the almanac. He then locates his younger self later that day at Western Auto, picking up his car - and having an argument with Terry over the $302.57 repair bill. As this goes on, Marty smuggles himself into the back seat of Biff's car.
- Accompanied by Babs, Lorraine has just picked up her outfit for the dance from Ruth's Frock Shop. As young Biff boasts to her that he will marry her someday, she rebuffs his advances. Biff is then about to jump into his car to drive home and get ready for the evening, when he encounters an elderly stranger occupying the driver’s seat. Although the stranger is mysteriously able to start the car, Biff apparently fails to recognize him as his older self, who then informs him that "Today’s your lucky day."
- Marty, hiding in the back seat of the car, is an intimate witness to the elderly Biff’s demonstration of the power of the almanac, but he does not interfere, as Doc has advised. The young Biff tells his older self he’ll "...take a look at it."
- 6:38 p.m. Thinking he’s done enough to change the future, and intending to escape detection, the elderly Biff departs in the DeLorean to the same moment he departed in 2015.
- 9:28 p.m. Marty retrieves the sports almanac from an unconscious Biff, while Doc departs the Lyon Estates construction site to fly towards the roof of Hill Valley High School.
- Marty fights off Match, Skinhead and 3-D and keeps them from jumping the younger Marty, allowing the events of that timeline to occur as they had before. Marty avoids any direct contact with his younger self, but loses the almanac to Biff again.
- Pursuing Biff, Marty ultimately retrieves the almanac from him. Biff crashes his '46 Ford a second time. Burning the almanac, Marty and Doc are able to visually confirm the erasure of the alternate 1985 throught items they had taken with them from that alternate future.
- 9:44 p.m. The hover-converted DeLorean, with Doc on board, gets unexpectedly struck by lightning just outside Lyon Estates and is sent seventy years back in time to January 1, 1885 due to an on-board malfunction Doc neglected to correct. This creates Timeline 12, which begins at Doc's entry point in 1885 and timeline 11 fades away.
- Saturday, November 12
- Unbeknownst to Marty and Doc at the time, the overload of the time circuits when the DeLorean got struck by lightning also caused the DeLorean to be temporally duplicated. The temporal duplicate DeLorean was simultaneously sent seventy years into the future to 2025.
- Back to the Future trilogy
- Back to the Future: The Game
- Episode 1: It's About Time (Mentioned only)
- Back to the Future (IDW Publishing)