Just some food for thought...
Look at yourself in a mirror. It takes light a quantifiable amount of time to reflect off your face, off the mirror, and into your eyes. So you are actually looking at yourself in the past. It is only a fraction of a fraction of a second in the past but it is still the past. In fact, everything you precieve is not happening, but has already happened. There is no present except your own thoughts in your head. Just for another example, it takes light from the sun 8 minutes to reach the earth so we never see the sun as it is now, but as it was 8 minutes ago.
And time "travel" is possible by manipulating the relative rate of the passage of time, but I do not believe simply "hopping" from one time to another is possible because time will always pass at a "normal" rate for you.
Consider this theoretical situation. Say you are on a vehicle that can travel at the speed of light. There is a clock at the point of departure and a clock at your destination and each end of the vehicle has a sophisticated theoretical telescope constantly fixed on each clock respectively. Now the vehicle accelerates to the speed of light. Looking back at the clock you left you would see it motionless since any light reflecting off the clock would not be able to reach you, you are an observer of a single moment in time. Time has "stopped". Now look at the clock ahead of you and what would you see?
This is also an interesting article about a quantum experiment that shows signs that the future can actually affect the present, which would mean the present could possibly affect the past.
http://discovermagazine.com/2010/apr/01-back-from-the-future