The thing is, as far as we can tell time travel can result in paradoxes which go on forever. I've heard so many examples of it yet I can't remember any of them.
You can slow time for specific people, though. If you get close enough to a major gravity well, such as a black hole (without getting destroyed by it, though) you can make time pass slower for yourself, which also makes you age slower. The specific example I heard was every 2 years for you is 10 years in the "normal" world.
I like time travel stories. I can't remember the name, but what was that story about the lumberjack who went to the forest and found two men playing a game of chess so he sat and watched for what seemed like a decent amount of time, but when the game was over he went back to his village and found out that many years had actually passed?
