Originally posted by: wmgan
In any case, the time travel aspect of Azkaban always bothered me. I think making time travel a possibility in Harry's world was the single worst mistake that Rowling made in the series, because that leads to the question -- why didn't Aurors USE them to stop Voldemort before he gained power? Or, if they were a recent invention and they couldn't go back too far, why not go back and stop Voldemort from coming back in GoF? Etc. etc. I love stories about time travel but only if that's the driving force behind the story (like Back to the Future, Lightning by Dean Koontz, etc.). Otherwise, introducing that factor tends to muddle things up.

I've actually been thinking about this, because you made me think about it in a way I hadn't considered before. But ultimately I realized why it wouldn't be able to work. Based on the book (and even more apparent in the movie) is that Rowling's view of a time travel is a fixed timeline, unlike, say, Back to the Future, where you can actually change events. For example, Harry saving himself and Hermione with the Patronus in all instances of that timeline, not just when he went back and did it. If Voldemort could have been stopped that way, then it would have already happened, and it obviously didn't.

More importantly, and probably logistically why no Auror would try it is because it would create a horrible paradox. If they did destroy Voldemort in the past, there would be no reason in the future for them to go back to the past and attempt it, which means that no one would, so Voldemort wouldn't be defeated, etc...