The Pleistocene era, more commonly known as the Ice Age, lasted from about 2586000 B.C. to 9700 B.C.
On April 15, 1986, Marcus Irving travels to January 8, 19654 B.C. in his Yugo time machine, temporarily stranding Marty McFly and Dr. Emmett Brown. They managed to escape sabre-tooth tigers shortly before Irving returned to bring them forward to 1997, as he was afraid of the butterfly effect their presence could cause that far in the past.
On May 2, 1991, Biff Tannen stole a DeLorean time machine from the Institute of Future Technology and traveled into the future to October 25, 2015. Doc used a sub-ether time-tracking scanner which allowed him to pilot an 8-passenger DeLorean time machine full of time travel volunteers to bump Biff's DeLorean to 88 m.p.h. and bring him back. However, Biff avoided them by traveling to October 25, 1000000 B.C., followed by October 25, 64000000 B.C., before he was finally brought back to 1991.
- Back to the Future: The Ride
- Universal Studios: Theme Park Adventure
- Back to the Future (IDW Publishing)