In the Back to the Future films, the longest jump seen on screen is from BTTF3; Marty's jump from 1885 to 1985, precisely 100 years into the future when he uses the stolen time-train to travel home.
The final scenes of BTTF3 (notably the fact that the Jules Verne has been hover-converted) would seem to suggest a jump from 1885 to 2015 (130 years into the future), but it's not made clear whether this happened in a single jump or multiple jumps.
In the TV show, Marty and the Doc travel back to the Jurassic age, approximately 180 million years ago. They encounter a dinosaur called Tiny.
In the BTTF ride, the riders experience a jump in to the Cretaceous period where they are attacked by a T-Rex, presumably somewhere around 68 million years into the past.