Marty and Doc arrive at night. They find a completely different Hill Valley. They try to figure out what happened. Marty confronts Biff. .... Doc arrives and incapacitates Biff, allowing him and Marty to flee to 1955. ~ 1 day. Marty secretly follows the 1955 Biff and witnesses him receive the almanac from his older self (November 12). More @Wikipedia
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