In order to save the world from a nuclear holocaust in 2045, Doc Brown must push the technological age back at least 50 years preventing Mattel Hoverboards and Mr. Fusion from being created.
2010
1972
2021
1966
2003
1976
1999
2019
1968
1988
2012
2015
2014
2017
1984
1997
2002
2001