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With the use of a time turner, that opens a whole "Pandora's Box" of possibilities. While the use of one can be problematical, when the Ministry of Magic found out how dangerous Voldemort was, why didn't they simply use a time turner to go back and stop him before he became dangerous?

(I know this does open a lot of plot holes, but witches and wizards don't seem to worry about laws of science, so it would seem strange that magic that seems to easily supersede laws of physics (like brooms that fly without propulsion) would worry about the problematical issues of time travel.)

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    Do you mean, this way youtu.be/YsYWT5Q_R_w ? ;)
    – ykombinator
    Feb 26, 2012 at 9:11
  • 4
    The only answer is that here is no answer, other than "that's how the author wrote it". Hence the reason I pretty much hate any science fiction involving time travel, as it almost inevitably leads to ridiculousness like this. The only show I've ever seen that wasn't ruined after introducing time travel was "Misfits" and that's only because it's supposed to be ridiculous anyway.
    – Kevin
    Apr 13, 2012 at 19:21
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    I always wonder instead : Why Voldemort did not use a Time Turner?
    – Matemáticos Chibchas
    Apr 19, 2013 at 0:15
  • 27
    More than a year after this was asked, and I still read it "Why couldn't Tina Turner have been used to stop Voldemort".
    – Avner Shahar-Kashtan
    May 30, 2013 at 7:13
  • 16
    For the same reason they didn't fly the One Ring to Mount Doom...
    – Gaius
    Apr 1, 2015 at 11:31

16 Answers 16

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This is specifically discussed in the Pottermore moment "The Time Turner". In short, time-turners cannot be used to affect major changes without incurring dire (but unspecified) consequences.

Using them to remove someone as important as Voldemort would, presumably result in massive ramifications:

Even the use of the very limited amount of Time-Turners at the Ministry’s disposal is hedged around with hundreds of laws. While not as potentially dangerous as skipping five centuries, the re-use of a single hour can still have dramatic consequences and the Ministry of Magic seeks the strictest guarantees if it permits the use of these rare and powerful objects. It would surprise most of the magical community to know that Time-Turners are generally only used to solve the most trivial problems of time-management and never for greater or more important purposes, because, as Saul Croaker tells us,

- “ just as the human mind cannot comprehend time, so it cannot comprehend the damage that will ensue if we presume to tamper with its laws. “

Obviously this is drastically subverted by the entire plot of Harry Potter and the Cursed Child where a new sort of time-turner (one capable of going back multiple years) is used to resurrect a major character.

The short answer would seem to be that you absolutely can use a multi-year time-turner this way, but that the Ministry would rather you didn't, in case there were any dire side-effects.

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    @Axelrod - On the contrary, causing that much damage to time sounds like the sort of thing that would rip the universe a new space-hole and kills us all.
    – Valorum
    Jan 22, 2016 at 18:52
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    @Axelrod - A previous time-traveler in the Potter universe (Eloise Mintumble) caused "great disturbance to the life paths of all those she met, changing the course of their lives so dramatically that no fewer than twenty-five of their descendants vanished in the present, having been “un-born”. Finally, there were alarming signs, during the days following Madam Mintumble’s recovery, that time itself had been disturbed by such a serious breach of its laws. Tuesday following her reappearance lasted two and a half full days, whereas Thursday shot by in the space of four hours."
    – Valorum
    Jan 22, 2016 at 18:56
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    That's terrible.
    – user40790
    Jan 22, 2016 at 19:09
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    @Axelrod - Well, it certainly was for poor Thursday.
    – Valorum
    Jan 22, 2016 at 19:10
  • 3
    Can you make horcruxes by ripping the space-time continuum instead of your soul?
    – Nacht
    Apr 2, 2017 at 22:57
57

I wasn't able to find a canonical answer to this, but I found one that is logical and lines up with the effects of Time-Turners in the books here.

Quoting from that page:

Luckily, time travel in Harry Potter doesn’t exactly work that way. The time traveler cannot change the past because what is experienced in the past has already been changed.

So the Ministry would be unable to go back in time and destroy Voldemort unless they already went back in time and destroyed Voldemort, thus negating the need to do so.

This lines up perfectly both with the book and movie versions of the events involving the time-turners. Remember in the movie, that Harry, Ron, and Hermione were alerted to the coming of the Ministry officials and Dumbledore when a rock mysteriously flew though the window and hit Harry. Later on, we see Hermione throwing the rock.

The book also falls into this pattern.

Note added for all of those that this doesn't make sense to

In science fiction, there have been several different ideas about what time travel entails. The time travel described in the Potterverse is described in the Wikipedia Time Travel article as Immutable time or predestination paradox. It's not unique to the Potterverse at all.

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    @Casebash, those things had already happened too. Recall that they didn't actually see Buckbeak get executed; they just saw the executioner swing his axe and heard a thud. Later we learn that he was just taking out his frustration on a pumpkin. Sirius' escape is even easier: he was locked in the tower, with nobody keeping watch. They actually helped him escape shortly before Dumbledore talked to Harry & co. in the hospital wing, they just didn't know it yet.
    – Joe White
    Feb 26, 2012 at 13:47
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    I can't believe this was accepted as the answer. It makes no sense whatsoever
    – Kevin
    Apr 13, 2012 at 19:15
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    This "already happened" philosophy is actually not really true, and here is why: remember that Hermione explained Harry that meeting yourself is dangerous and a lot of wizards killed their past or future selves. Killing your past self is definitely not consistent with the "already happened" theory because if you are killed in the present, you won't be able to travel in time in the future. So apparently there's more to the theory.
    – Malcolm
    May 24, 2012 at 21:30
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    @NominSim - they don't go back to change the past, they go back to save Sirious & Buckbeat, something they'd already done at that past point, so effectively they just go back to the past to "fulfil" that bit of their future. It makes perfect sense if you assume that you can't change history - read the link David Stratton posted in his edit.
    – Nick Shaw
    May 25, 2012 at 8:03
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    No, the history is the way it is because they came back and affected it, which locks them into doing it again. really, this is standard fixed, unalterable, time travel. It's the only one that allows an orderly universe that obeys rules, and does not allow for alternate realities. Once you allow for alternate realities, you star wondering if earth 1218 is the only one, I mean what if Wolverine doesn't have a healing factor in another universe because of something Spartacus did to eliminate the mutant gene?
    – David Stratton
    May 26, 2012 at 0:09
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+250

From JK Rowling's entry on time-turners on Pottermore:

According to Professor Saul Croaker, who has spent his entire career in the Department of Mysteries studying time-magic:

'As our investigations currently stand, the longest period that may be relived without the possibility of serious harm to the traveller or to time itself is around five hours.'

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    Ooo, that's interesting! I must catch up on Pottermore. Here's a well-written article on time travel in Harry Potter that I've read quite a few times when time-turner questions have come up. Thanks for leaving this new information. +1
    – Slytherincess
    Aug 5, 2013 at 14:42
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Remember what Reg says in Douglas Adams' Dirk Gently's Holistic Detective Agency? He claims he's tried to fix some similar problems in history by using time travel, but that those attemts have always backfired and have turned something else much worse.

Remember this conversation of Harry and Dumbledore in the Prisoner of Azkaban?

‘But – I stopped Sirius and Professor Lupin killing Pettrigrew! That makes it my fault, if Voldemort comes back!’

‘It does not,’ said Dumbledore quietly. ‘Hasn't your experience with the Time-Turner taught you anything, Harry? The consequences of our actions are always so complicated, so diverse, that predicting the future is a very difficult business indeed … […] You did a very noble thing, in saving Pettigrew's life.’

If Harry is effectively helped Voldemort rise again with what seemed like a noble action, would you dare to go back in time several decades to kill the young Riddle and bear all the consequences of your action? Could you be sure you're acting for the better in the end?

Remember what Gandalf answers when Frodo asks why he ordered to keep Gollum captive instead of killing him?

“[...] He deserves death.”

“Deserves it! I daresay he does. Many that live deserve death. And some that die deserve life. Can you give it to them? […]”

You have to be very careful before you demand to kill people for their sins.

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    I love this answer!! except that then, perhaps, using the time turner in the first place should not have happened.
    – balanced mama
    Dec 8, 2013 at 1:19
  • 5
    This reminds me of a large number of sci-fi universes where they try to go back in time and kill Hitler to stop WW2 from ever happening, and then something even worse happens (like the Soviets getting too strong and starting a war even more horrible than WW2, etc.)
    – vsz
    Jan 4, 2014 at 14:00
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I finally found the answer to this question today. I was reading the books again and saw this passage in Order of the Phoenix, during the Battle at the Ministry:

Harry stuck his head out of the door and looked around cautiously. The baby-headed Death Eater was screaming and banging into things, toppling grandfather clocks and overturning desks, bawling and confused, while the glass-fronted cabinet that Harry now suspected had contained Time-Turners continued to fall, shatter and repair itself on the wall behind them.

Then in Half Blood Prince, after Aragog dies, Hermione mentions this in a conversation with Hagrid:

‘... I don’ reckon it’d be safe fer anyone but me ter go near the colony at the mo’,’ Hagrid finished, blowing his nose hard on his apron and looking up. ‘But thanks fer offerin’, Hermione ... it means a lot ...’
After that the atmosphere lightened considerably, for although neither Harry nor Ron had shown any inclination to go and feed giant grubs to a murderous, gargantuan spider, Hagrid seemed to take it for granted that they would have liked to have done and became his usual self once more.
‘Ar, I always knew yeh’d find it hard ter squeeze me inter yeh timetables,’ he said gruffly, pouring them more tea. ‘Even if yeh applied fer Time-Turners –’
‘We couldn’t have done,’ said Hermione. ‘We smashed the entire stock of Ministry Time-Turners when we were there in the summer. It was in the Daily Prophet.’

So the reason they couldn't use Time-Turners to fight Voldemort is simply that there weren't any more. The entire stock was destroyed. They couldn't even turn back time to before they were destroyed, because there wouldn't be any left with which to turn back time to begin with. :)

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    But why didn't they use them before Harry was born or when he was young? If the only reason is because they were destroyed, seems to me they waited way to long to use them. If they were going to use them shouldn't they have done so when he first came to power?
    – xecaps12
    Apr 7, 2012 at 2:36
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    Because they didn't know the extent of his power yet. They knew he was a really powerful dark wizard, but assumed he died when he attacked Harry. Remember, the Ministry controlled the Time-Turners. They were really hard to get. By the time Dumbledore knew Voldemort had returned, the Ministry refused to acknowledge it until after the Time Turners were destroyed. Fudge certainly wouldn't just hand a Time-Turner out to go back and stop someone who already was dead, especially when considering the difficulty of doing so without creating a paradox.
    – Gabe Willard
    Apr 7, 2012 at 2:48
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    That is only a stock of un-used time turners though. What about ones already out in the world? +1 anyway for a clear and canon answer.
    – balanced mama
    Dec 8, 2013 at 1:23
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If you remember when the existence and use of the time-turner was introduced in Book 3, Dumbledore said in the hospital wing to Hermione, "three turns should do it" for three hours. Now I don't think it was addressed ever that you could set it for hours, days, weeks, etc so I believe it was only in hours. Now say they went back in time to stop Tom Riddle when he was in Hogwarts, 50 years ago. 365 days in a year, 24 hours per day so to go back in time one day they would need to turn it 24 times. 50 years, 365 x 50 = 18,250 days. 18,250 x 24 for the hours = 480,000. Goodluck turning it 480,000 times. Same concept even if they went back a little earlier than that.

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    Yes, you're right. It would be really difficult for Harry and Hermione to use the Time Turner at that point, but someone could have used it waaaaay earlier on - like when Voldemort first started to come to power.
    – phantom42
    Oct 15, 2013 at 20:23
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    Someone's been watching HISHE :)
    – DVK-on-Ahch-To
    Oct 15, 2013 at 21:41
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    Gee, if only there was some sort of supernatural force the characters could command to turn it 480,000 times for them....
    – jwodder
    Oct 15, 2013 at 21:43
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    Nobody said it had to be turned by hand and not by a spell or some other contrivance. But, even more so, there's no indication that time turner (or others) cannot be set for a day - or that a turn isn't an hour and that the amount each turn lasts is linear and not logarithmic. But if it would save many lives, I'm sure there are those who would have been willing to turn it half a million times to bring back a loved one.
    – Tango
    Oct 16, 2013 at 6:18
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    480,000 and a few more to account for leap years :-)
    – maguirenumber6
    Apr 2, 2015 at 12:56
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Because this would create a paradox (http://en.wikipedia.org/wiki/Bootstrap_paradox).

Let's say Dumbledore went back in time to kill Voldemort when he was a child. Once he killed Voldemort, Voldemort would obviously no longer exist. Therefore, the reason why Dumbledore went back in time (i.e. Voldemort) wouldn't exist either - making this scenario impossible.

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  • That's very easily solved - after killing Voldemort, Dumbledore leaves a note for himself telling him what to do...
    – komodosp
    Jul 31, 2022 at 9:58
2

Time turners are for strictly academic use. It would be incredibly dangerous to go back and kill someone that we knew existed. See every story dealing with time travel.

Hermione was able to use one because she didn't interact with herself. If she ever was found to use it in some other way, she could get in huge trouble, and not just from the law. Time travel is very dangerous stuff, not worth risking, even for such a noble cause.

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  • Who said anything about killing him? If it were early enough, Azakaban would have done the job. Do you have a reference about the "only for academic use" issue?
    – Tango
    Feb 26, 2012 at 4:34
  • @TangoOversway: No, other than that's the only purpose they are even hinted at in the series. And even tossing him in Azkaban would have been just as dangerous...
    – PearsonArtPhoto
    Feb 26, 2012 at 4:35
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    Of course, they do interact with themselves by throwing the rock through the window at Hagrid's.
    – Ken Liu
    Apr 11, 2012 at 16:04
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    Time travel is very dangerous stuff, not worth risking, even for such a noble cause. But it is fine to take a few more classes in high school ^_~
    – Sardathrion - against SE abuse
    Apr 12, 2012 at 9:50
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    Of course, they do interact with themselves by throwing the rock through the window at Hagrid's and let's completely ignore the patronus?
    – Rob
    Apr 12, 2012 at 15:29
2

Harry Potter and the Prisoner of Askaban "Horrible things happen to wizards who meddle with time, Harry."- Hermione Granger to Harry Potter

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While not explained in the books in much detail, we can guess at its functionality from the ways it was used. It seems that time turners have two major laws governing their functionality:

  1. Their range is limited, they can only take you back a few hours at most (confirmed in an interview what Treborcram mentioned in another answer)

  2. They cannot violate causality, in the sense they don't allow you to change anything which was observed. So if you look at a glass for an hour, you can't go back in time an hour an smash it. Had they witnessed the hippogriff's execution, they could have probably been unable to go back in time and save it.

If we want to be really picky, we can even define "observed" in a quantum physics kind of way. There is a fan fic which greatly expands on the use of time turners, and remains consistent with the original books in their capabilities.

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  • Even if it has a limited "range", that doesn't explain why someone did/could not use a time turner more immediately after Voldemort began his attacks. Similarly, someone who was not present at, say a murder, could go back and stop the murder.
    – phantom42
    Jan 4, 2014 at 16:20
  • phantom42 : in this case we have to go with the "all time turners were destroyed in the battle at the ministry" concept. It happened before it was officially acknowledged that Voldemort is back.
    – vsz
    Jan 4, 2014 at 18:05
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    In HPMOR, time turners are used tactically to call for aid any time, anywhere. You are attacked, you call for help, and the aurors can go back in time, mount broomsticks, and arrive at the exact time when you were attacked (so they don't violate causality)
    – vsz
    Jan 4, 2014 at 18:08
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Things you do in the present change the future. Thing you've done in the past changed the present. In the theory of multi-history, history will change toward what you've done in the past. Every decision will make a different history. May be someone tried to go to the past and kill Voldemort, and the history went another route. Our story goes to another history route where they didn't do it. Just enjoy the movies and books :)

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  • I couldn't find anything called the theory of multi-history -- is this a scientific theory? Did you possibly mean the Chaos Theory? :)
    – Slytherincess
    Apr 14, 2012 at 2:54
  • Yah, a scientific theory. I don't remember who is creator of hits. Please try 'Brief History of Time', author: Stephen Hawking, I lost my book years ago. May be it's one you mentioned. Not sure what it called in English, I read one in my native language, sorry :)
    – Shinigamae
    Apr 14, 2012 at 8:51
  • Well, it's not really my responsibility to authenticate the sources in your answer :) IMO, if you're going to cite a specific theory, you need to be prepared to provide a source for the works that you're basing your answer on. Sources are important at this site because anyone can claim a theory or quote is authentic. Unless you have something to back it up, it's really only conjecture. :)
    – Slytherincess
    Apr 14, 2012 at 14:10
  • Oh got it. I'm just passing by because the topic about HP :) really my knowledge of science is narrow, just say what I think about the topic, not to instruct anyone to a theory. But I really got what you want to tell 'Sources are important at this site'. I'm new here and it is the first rule I know.
    – Shinigamae
    Apr 14, 2012 at 18:02
  • I think that source was Back to the Future.
    – Cees Timmerman
    May 25, 2012 at 13:33
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I like to take the "You've already travelled back in time" stance. The Time Turner works by sending you to the past. Anything you do in the past, you've already done. If someone had killed Voldemort, he would have never been alive to kill people and become a threat, meaning that there would be no reason to go back in time.

For an easier to understand (for me) example, let's say you walk into a room, and your future self gives you a high-five and leaves the room. When you travel back in time, you have to give your past self a high-five. Maybe you were always planning to do that. Maybe you were planning to do something else but slipped. Maybe magic itself forced you to conform to the timeline. Either way, you just high-fived your past self, who will go back in time and go through the same issue you did.

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    This adds nothing to any of the existing, more detailed answers.
    – Chenmunka
    Jul 14, 2015 at 14:17
0

In Harry Potter and the Prisoner of Azkaban, when Harry and Hermione go back in time, what they did had already happened. Had someone gone back in time to stop Voldemort and succeeded, Voldemort would never have killed Lily and James, and the series would never have happened. However, someone would have had to have enough awareness of this to go back in time and stop Voldemort.
I hope this helps; I don't think I phrased it very clearly.

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-1

From Harry Potter and the Half Blood Prince:

"'Ar' I always knew yeh'd find it hard ter squeeze me inter yeh timetable," [Hagrid] said gruffly, pouring them more tea. "Even if yeh apploed for Time-Turners -"

"We couldn't have done," said Hermione. "We smashed the entire stock of ministry Time-Turners when we were there in the summer. It was in the Daily Prophet."

  • Chapter 11, Page 218, Paragraphs 4-5

Stop bringing up this argument. They smashed every single time turner in the battle at the end of book 5, time turners (I'm assuming) are too complicated for some average Joe to make, and I doubt a Voldemort-controlled Ministry would be allowed to make any. This is not a plot hole, even the 'How It Should Have Ended' Harry Potter parody caught this non-plot-hole when Harry said "Hermione, something might conveniently destroy the time turners making that the last one, you'd got to keep it"

(the scene I'm quoting is at about 0:58)

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    This was already mentioned in GabeWillard's answer, and comments in there even bring up the issue of, why weren't they used before Voldemort tried to kill Harry as a baby?
    – Izkata
    Apr 18, 2013 at 2:25
-1

paradox theory is the simple reason and used in many scifi to explain this same issue. see time machien for me. pretty much if you go back in time to change the event that made you go back in time int he first place then you never go back in time to alter the event. it makes a wibbly wobbly loop known simpley as a paradox and it writes itself out.

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Then the person would have to relive all of the years he had experienced, up until the present time. Who would want to do that? I might add that he would have to remain hidden from other people.

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    (1) This is little more than a duplicate of Floaty's answer from Sep 25, 2014 (which got downvoted) and others before it.  (2) The Potterverse is full of heroes, including many who would be willing to die to save others.  (In fact, Lily did die to save Harry.)  There probably would have been plenty of volunteers to make this much lesser sacrifice in order to save the thousands of people Voldemort and the Death Eaters tortured and/or killed.
    – Peregrine Rook
    Jan 22, 2016 at 18:40
  • Thank you Milo for correcting my English. I know that there are many heroes in Potterverse but think about it. They'll have to live alongside their past self and what are they gonna do about the fact that there are two of them (Different age, maybe)
    – Terrence Callaghan
    Jan 24, 2016 at 15:35
  • (1) I did think about it.  I know Dumbledore said that there are things worse than death, but I believe that he would rank torture, and surviving the torture and/or death of your loved ones, as worse than living a life in hiding.  (2) "Different age, maybe"?  How can a time-traveler possibly be the same age as his past self?
    – Peregrine Rook
    Jan 24, 2016 at 17:57
  • What about their identification? You can't possibly have data of two same person. Oh, about that, what I meant to say was the life stages, adolescence, teenager, child, etc.. My English is so bad, sorry.
    – Terrence Callaghan
    Jan 26, 2016 at 6:54

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