As much as I would like to travel through time their would only be limited times that you could travel to without also traveling trough space because: The earth is moving around the sun as well as moving outwards through the verse so to move to the time of the dinosaurs you would have to make a few jumps so that you don't come out somewhere in space where the earth is going to be in a few billion years
Space. The concept of time traveling to the past seems...implausible to me. To the future, maybe, but once you go back to the past, you'll wind up back to the present where you left in the first place and then you'd be stuck going back because that's the present. It just seems like you'd be stuck in an inevitable loop. Also, if that loop weren't to happen, I'd imagine going back and changing things would just mess everything up in the present/future.