Major plot hole in the Harry Potter series

In Harry Potter and the prisoner of Azkaban, they use a necklace that goes back in time called Time-Turner, nothing is mentioned about how much you're allowed to go back. So if that's the case, why didn't every single death in the series, every major catastrophic event get prevented, by simply travelling back in time and not let it happen? seriously every single event could be corrected!! how about going back in time and preventing Voldemort from taking over Hogwarts, for a start? or how about Snape prevents Voldemort from killing Lilly Potter? the possibilities are endless.

I think that is somewhat covered when, at least in the movie, Dumbledore says, "you know the law Ms. Granger", implying that there are specific events that may be altered.
I don't know for sure, sort of grasping at straws here a little bit. Let us remember that it is a movie, of course, and several conclusions can be drawn.

Not a plot hole, people just didn't use their resources correctly. Happened a lot in Harry Potter and happens in other movies/tv shows/anime/etc. too.

Well , it could be that you can go back in time to prevent death, but only before it happens! Once that it happens it is impossible: Even Dumbledore can not come from the Death- minister of Magic dialogue in HP7. For surre that the minister knew about time turners - remember Minerva had to ask permission from the ministry

I think it's actually troubling that the school gives what is essentially a time machine to a 13 yr. old just so she can take an extra class. Just..why? Then when Dumbledore says how dangerous they are..why would you give one to a teenager? Yes, Hermione is pretty responsible for a girl her age, but she is still a teenager. I mean what are the requirements for getting one? Could someone like Malfoy of gotten one if he wanted to take an extra class?

Anyways, I seem to recall at one point they said all the time turners were destroyed.

Originally posted by Unicor777
Well , it could be that you can go back in time to prevent death, but only before it happens! Once that it happens it is impossible: Even Dumbledore can not come from the Death- minister of Magic dialogue in HP7. For surre that the minister knew about time turners - remember Minerva had to ask permission from the ministry

This does not make any sense though. Buckbeak was killed, but then they went back and saved him.

I'm sure their are laws that need to be followed, and causality effects.

Originally posted by Darth Abonis
I'm sure their are laws that need to be followed, and causality effects.

Originally posted by Surtur
I think it's actually troubling that the school gives what is essentially a time machine to a 13 yr. old just so she can take an extra class. Just..why? Then when Dumbledore says how dangerous they are..why would you give one to a teenager? Yes, Hermione is pretty responsible for a girl her age, but she is still a teenager. I mean what are the requirements for getting one? Could someone like Malfoy of gotten one if he wanted to take an extra class?

Anyways, I seem to recall at one point they said all the time turners were destroyed.

This does not make any sense though. Buckbeak was killed, but then they went back and saved him.

In the OotP book, when Dumbledore's Army is in the Dept. of Mysteries, we learn that they smash all of the rest of the Time Turners. So goodbye MacGuffin.

Personally I don't think it's necessary to be a fault since in most fantasy worlds, travelling through time often deemed as "forbidden art". The idea is that, when we change something that already happened in the past, we can't predict what else will change (just like the Butterfly effect). I remember in Marvel Universe, Flash ran back in time to rescue his mother, but that also wrecked the timeline.
Also this can open another question: we see that there are many powerful gods in many Universes. For example, Zen-oh and grand priests of Dragon Ball Universe: if Frieza, Black Goku and many other dangerous evils can wreck things, why the gods don't interfere in the first place?

Originally posted by NotAllThatEvil
Buyback didn't die. Harry potter time travel is linear.

Buckbeak did die the first time around though. Unless the suggestion is seriously that he didn't die and Hagrid nor anyone else decided to mention this fact to Harry and his friends.

Hagrid especially has no reason to never mention this, as he had no idea timey wimey shenanigans were going on.

Rowling admits that the Time-Turner was really bad idea) She destroyed all of them in the 5 part because of it

Time travel always complicates things.