I'm going back in time 24hrs. The next 10 people to post in this thread get £10k from my lottery winnings.
Of more concern:
Imagine you are sitting in your time traveling machine on planet earth and you go back in time 100 years. The earth rotating about the sun, and the sun rotating about the galaxy, and the universe expanding etc etc. The earth isn't in the same point in space anymore!
So when you travel in time, you also have to travel in space exactly according to a fixed point of reference. If you are off by a tiny, tiny amount, your flotsam in space.