If the Many Worlds Interpretation of quantum physics is correct, then time travel is synonymous with sliding between parallel worlds. Every single jump to a different time would create a new world line due to the insertion of new causations. The interesting side effect of this is that one could effectively reverse entropy in one world line by taking energy from another world line and transferring it to the target world line. This would violate the conservation of energy locally within world line, but not globally when including all world lines. Interestingly, this would also suggest that there is infinite global energy between all possible world lines. Somehow, one wonders if this means conservation of energy should prohibit time travel.
In practice however, this is not an issue, because time travel requires such enormous amounts of energy that it is generally impossible to transfer enough energy to make up for the cost of transport.