Unfortunately, time travel via wormhole isn't possible. Sorry. Here's why:

Picture an ant on a piece of paper. That's us, on the fabric of space. Now, wrap the paper into a tube, with the ant on the inside. that's us on space-time. Now, if the ant wants to go back in time, he needs to go through the paper and to the point he needs to be, then back through. This requires a wormhole.

Scientific American says we can make wormholes. In order ot amke one large enough to transport a person / thing, we'd need all the matter in the universe's worth of energy just to go IN, then the same amount to come back out. Einstein proved that with E = mc^2, proving effectively the only way to travel in time is to travel very very fast, and the only way to create a wormhole of any significance is with energy equivalent to many many times what you're transporting.

I know, it sucks.

But that's physics for you. Now, if you're into supersring theory and bvelieve in the testament of human perserverance, you might say we'll eventually be able to bend the 10th dimension, so we can simply WALK into the past. That, however, is far, far FAR off.

Also, if time travel were possible, wouldn't we already know?