Yep, time travel is taking place all the time(boy, I hate that phrase). In one direction, but always.

According to Einstein of course... it can go at different rates, depending upon your speed, or even an enormous warping of space-time caused by gravity can affect it.

According to my physics teacher, if you were to go a quarter of a way into a certain black hole's event horizon, held in place by a powerful spaceship, and waited there for ten seconds, then pulled yourself out... 10 thousand years would pass.

I think most of us would probably prefer to stick with normal time travel. Still... it's interesting to think that the concept of manipulating time is no longer just science fiction.