There is nothing like time travel in a movie to get your head spinning. Who is going where and what happens when they get to the future and how does that impact the past? It's enough to make your head hurt and nose bleed (that's why they called it "time travel sickness" on Lost).
The mysterious Mr. Dalliard made this awesome graphic of the ways that people have traveled through time, what that means for them, and just how they did it. Hopefully this makes the journey through time a little bit easier to swallow:
Click On Image To Expand.