Consider the magic power of being able to 'reset time' in the style of Groundhog Day or The Edge of Tomorrow, ie revert one's environment and physical state to that of an earlier time while retaining memories of the previous timeline, then being able to relive or change that timeline (and being the only person who is aware that there ever was an alternative). Let's say that unlike some examples, it is not necessary to die to invoke this ability, it can be done 'at will', and that the distance back in time that a resetter jumps is not fixed, but controllable within a range that reflects their own natural ability and training.

Given that, the 'level 1' ability to jump back, say, 24 hours, is actually nowhere near as convenient or powerful as the ability to reset a shorter length of time: instead of getting wounded in a battle and having to reset the whole day and fight the whole battle again successfully as you did before until you get to the part you wanted to change, it would be more useful to be able to just jump back 10 mins (or less) and only have to re-fight the most recent stages.

This is especially true since I'm imagining butterfly effects to have a pronounced impact at making the 'new reality' diverge fairly quickly from the old one, at least on a local level. In particular, stochastic processes (like rolling dice) can't be reliably reproduced more than a few metre-seconds from the warlock's world-line.

Fighting warlocks with the ability to do 'short resets' are therefore potentially more valuable than those who can only do 'long resets', and for an ordinary leader looking to hire a warlock as a bodyguard (because they make great bodyguards), testing the range of their power is important.

It's easy for a warlock to prove that they are able to time-reset at all: you choose a random phrase and write it down, then some time later the warlock tells you what you wrote; if they get it wrong you tell them what the phrase was so they can reset and know it (although if the warlock is legitimate, you'll never see this outcome); if they get it right then they must be legit. It's also possible to test that a warlock can reset at least a certain length of time: you write down a random phrase, then a few minutes later the warlock writes something down and gives it to you (having reset into that intervening period with the future knowledge of the answer); then after the designated length of time you open both papers and compare them, showing the warlock if appropriate; the warlock needs to be able to reset back at least as far as the gap to provide the right answer.

What test can validate a warlocks' claim to be able to reset at most a certain length of time?

If a warlock is actually only able to jump back six hours but claims to be able to do one, I can't seem to devise a test that can't be fooled by the warlock taking the necessary knowledge, waiting five hours until the required 'landing time' comes within their range, then going back and pretending they jumped back one hour when they said they did. Other than methods which involve the warlock getting executed, which I'd prefer to avoid.

A few clarifications:

  • There is no way for a non-warlock to detect when a warlock has reset.
  • The butterfly effect from the warlock acting slightly differently after a reset can be reduced with careful training, but cannot be entirely eliminated. For instance, asking the warlock to shake a cup of dice would almost certainly change the result of the throw if the warlock reset to before the shake.
  • Multiple warlocks exist (and their interaction is something I'm still grappling with), but the test should not require additional warlocks, and ideally should be immune to cheating by them (ie the candidate is not a warlock themselves, but has the assistance of someone who is).
  • $\begingroup$ A power like that of Max Caulfield in the video game Life is Strange, then? $\endgroup$ – Joachim Aug 28 '19 at 16:43
  • $\begingroup$ surprise them and knock them out and put them in a pit see how long they have to be unconscious before they stay in the pit. $\endgroup$ – John Aug 28 '19 at 17:00
  • $\begingroup$ @John humans don't tend to take kindly to being knocked out and thrown into a pit, nor do their brains. $\endgroup$ – abestrange Aug 28 '19 at 21:07
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    $\begingroup$ What you are calling 'time-resetting' is actually short-range time travel. The warlock goes to the state he was in at the time he arrived, but with knowledge of subsequent. Effectively it's only the warlock's mind, knowledge & memory that has been shifted back in time. Time-resetting per se would involve changing the warlock's surroundings in an earlier state while retaining his knowledge & memories etc. Interestingly this will have to have a limit or a range. Changing the entire universe is excessive. $\endgroup$ – a4android Aug 29 '19 at 6:21
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    $\begingroup$ No smart warlock would admit to having this power, let alone prove what the limits of its range were. Only dumb warlocks would stick their necks out by proving the limits of their power. $\endgroup$ – a4android Aug 29 '19 at 6:28

You actually gave the answer in your parameters.

Shake a cup of dice. Both you and the warlock memorize the results. Wait 59 minutes, then write your secret phrase. A warlock who has jumped back an hour or less will be able to write down both the dice roll and the phrase. A warlock who has jumped back further will have a different result on the dice roll. Do not yet reveal the secret phrase.

Edit in response to comments: Immediately roll the dice a second time and have the warlock memorize the result. He is now bound by two random events he cannot predict through time jumping. Wait 5 minutes and then have the warlock recite the second dice roll and reveal his written answers. A warlock who has waited past the second dice roll in order to jump back more than an hour and land in between will be wrong on the second dice roll.

  • $\begingroup$ Does this prevent a warlock from waiting five further hours, then jumping back to the correct time (but using a longer jump than the one they're claiming to be capable of)? $\endgroup$ – Stephen Aug 28 '19 at 19:23
  • $\begingroup$ That's a good point. Editing to account for this $\endgroup$ – IAntoniazzi Aug 28 '19 at 19:38
  • $\begingroup$ One problem I see with this, is that dice rolls are not truly random. Unless the warlock influences the way the dice-roller shakes the cup, the result will be identical. $\endgroup$ – Arkenstein XII Aug 28 '19 at 20:09
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    $\begingroup$ In OP's parameters they stated that a dice roll is sufficiently random that the result would change if the warlock reset. $\endgroup$ – IAntoniazzi Aug 28 '19 at 20:11
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    $\begingroup$ The trouble with this is that because you as a non-warlock don't retain your memory during resets, you won't remember the original result of the second dice roll; you'll only remember the result from the 'final' iteration $\endgroup$ – Stephen Aug 28 '19 at 22:38

There's a foolproof way you can test it, but it requires a special setup and program.

Basic explanation:

  • Lock the testee in a special room for 24 hours
  • Door is locked by a randomized password
  • Every 15 minutes (or how ever frequently you want) the password is re-randomized
  • At the end of 24 hours, the testee may request what the password was at ONE point in time
  • They then go back as recently as possible and unlock the door, leaving the test room
  • See how close to the end of 24 hours they emerge

If they go back too far, the passwords will be re-randomized and no longer valid by the time they would be activated.

Use a huge array of sensors to feed into the password randomizer to ensure high enough entropy, including biometric sensors, infrared and visible camera feeds, pressure sensors in the floor, humidity sensors, and hell even use their browsing data or gameplay input for while they're burning 24 hours.

Generate passwords that are a long string of random words so its possible to memorize but impossible to brute force, such as: "Correct battery horse staple"


W6 can go back 6 hours. He goes into the cell at 00:00 and waits in the cell until 24:00. He then uses a terminal to request the password for 18:00-18:15 and memorizes it. He then goes back to 18:04, unlocks the door, and walks out.

If W6 gets the password for 19:00, goes back to 18:06, tries to unlock at 19:00, it will fail because it will have been randomly re-generated. Now he'll have to wait until 24:00 to try again.

EDIT: Oh and if they don't leave the room before 24:05, slowly flood the room with poisonous gas to force them to jump back in time. This prevents them from waiting around after the test to make a 6 hour jump look like a 5 hour jump.

EDIT 2: OP does not specify if this takes place in the modern age. However, this approach can still work without any modern tech. Use a well secured cell that the testee can't simply break out of. Then use your preferred physical random number generator to give you sufficiently large numbers, and use those to choose words from a dictionary.

Have this done at an undisclosed location decently far away, and have a messenger deliver the testee's time slot password request and then their ultimate answer. Also burn the password list after the 24 hour test.

No computers are necessary for this, they just makes it easier and less prone to human error / influence.

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    $\begingroup$ Won't work. Let's say that in the first timeline W6 is tested in, the randomly generated password for 1800-1815 was "correct battery horse staple". But when W6 jumps back, because random events can turn out differently, the password won't be the same: it could be "union albatross pixel foggy". So even if W6 is being honest, they won't be able to get out. $\endgroup$ – Keith Morrison Aug 28 '19 at 22:24
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    $\begingroup$ Random events can only turn out differently from the point that the person jumped back to onward. So in Timeline 1, at 18:00 the password was set in the program, and at 18:15 a new one would be generated. Jumping from 24:00 in Timeline 1 to 18:06 in Timeline 2 would have the same password on file, since it was generated at 17:59.999. The divergence point for timelines is after the password generation point. From my understanding, going back in time wouldn't change any random event that happened in the timeline before the jump destination. $\endgroup$ – abestrange Aug 28 '19 at 22:41
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    $\begingroup$ Okay, my mistake. At first blush, that looks like it would work. $\endgroup$ – Keith Morrison Aug 29 '19 at 6:32

What test can validate a warlocks' claim to be able to reset at most a certain length of time?

I think you are focussing on the wrong metric to measure warlock effectiveness. Rather, measure their effectiveness by how favorable an outcome they can get for you, by using their time rewind ability, in an independent set of events.

In real life, while this ability of time reset may be usable countless times, it is bound to produce some fatigue on the warlock. A good warlock then is one who can make use of his abilities to get the best outcome in as many resets as doesn't burn them out.

For example, set up a game of football such that you have the best 11 players of the state play against warlock + 10 very bad players, and the measure of warlock's success is how favorable an outcome he can get from those these 10 bad players. Like not being completely routed, to making good number of saves, to having level scores, to actually winning.

In fact, if you had multiple warlocks to evaluate, you could set a tournament of such matches - with every warlock having the ability to reset, the one who can stay the longest with the matches all swinging in his favor wins.

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    $\begingroup$ I think this is the optimum answer; give practical tests and see what the outcome is, and base the decision on that. It would be like a baseball team testing a batter; they might have utterly atrocious technique, but if it works, who cares? $\endgroup$ – Keith Morrison Aug 28 '19 at 22:33
  • $\begingroup$ Right. the ability to jump short distances only benefits the warlock; his employer couldn't care less how tedious the repetitions are. $\endgroup$ – ths Aug 30 '19 at 13:53

Give them multiple tests, with increasing waiting time. First test: you reveal the answer after 1 hour, second test after 2 etc.

With this method sooner or later their landing spot will get out of range to answer the question in time!

When they start to get wrong, or hesitate, to get more time on order for their landing spot to get in range, that's when you get them.

  • $\begingroup$ I can intentionally answer wrong past the first hour if I so choose. This invalidates the waiting period. I can artificially shorten but not artificially lengthen the amount of time. $\endgroup$ – IT Alex Aug 28 '19 at 16:16
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    $\begingroup$ Also, as a non-warlock myself, I cannot see the timelines in which they hesitate. Ultimately, I only see the timeline in which they present their 'final answer'. The test needs to be designed in such a way that the only thing the warlock could have done to get the right answer, involves a reset of the correct duration. $\endgroup$ – Stephen Aug 28 '19 at 17:52
  • $\begingroup$ Further, suppose I can only jump 6 hours. I get the answer for the 1 hour, and reset. Then I just pretend not to know for five hours, and when the appropriate time comes, voila. $\endgroup$ – Keith Morrison Aug 28 '19 at 22:32

Let's say we want to test a warlock for 5 minutes.

  • Have 4 ten-sided dice in a cup.

  • At t=0 roll the dice by inverting the cup onto a table. The result is now determined but no-one knows what it is until the cup is lifted up.

  • At t=1 min the warlock must answer what the numbers are.

  • At t=6 min The cup is lifted to reveal to answer to everyone.

  • At t=7 min If the warlock was wrong, he is killed.

Only a good-quality warlock would still be alive after 7 minutes. He would have the t=6-7min period to memorise the 4 numbers and shift back to the t=0-1min landing-zone.

A poor-quality warlock would not actually be killed because he would just shift to a few hours before the test and try again (or decline the job). Each time he tries there will be a different number. Potential he could just keep trying until be gets lucky but it would take on average 10000 attempts. At one hour each, that's more than a solid year of 24/7 testing.

The only way the candidate would be killed is if they had no time-reset ability at all and you could screen out suicidal non-warlocks with a preliminary test.

  • $\begingroup$ I'm leaning towards the conclusion that killing the warlocks (or doing something else to force them to curtail their future time branches) is an inevitable part of the test. I was hoping that someone could devise a 'non-lethal' logic construct. But I guess threatening to kill a time-reverser any further in the future than "I already shot you in the head" is actually not really a threat at all; warlocks would probably have a much more pragmatic approach to death and injury than humans in general. $\endgroup$ – Stephen Aug 30 '19 at 9:25
  • $\begingroup$ The alternative is to magic-up a way to make them forget what the correct answer was after their time limit has expired. $\endgroup$ – smatterer Aug 30 '19 at 9:34

Have all the warlocks stay in a special room for whatever your minimum timeframe for employment is. (let's say 6-8 hours for a minimum jump time as the upper limit).

Surprise them at the end with a situation that would force a quick jump (assuming they will go for a short jump by default). The shock should carry back with them causing a visible reaction in the timeline they jump back to. Use that to gauge the minimum jump distance.

Alternatively, have jumping have a visible tick by default as well (something hard to fake).

  • $\begingroup$ If I understand the original poster right, all warlocks can do long resets but as they get better they gain the ability to do shorter resets, but don't lose the ability to do longer ones as he says that there are some that "can only" do long resets and others that "can" do short resets. $\endgroup$ – Samuel Robert Aug 28 '19 at 16:31
  • $\begingroup$ Indeed, all warlocks begin with the ability to reset to a range of times around 24 hours; with training and experience they can expand their range forwards and/or backwards, but retain all the range they previously had. Longer-range warlocks are definitely valuable, but for different purposes. For the specific purpose of close-range bodyguard, I think a well-developed short range would be more valuable? $\endgroup$ – Stephen Aug 28 '19 at 18:01
  • $\begingroup$ I misconstrued the original question. I will be editing shortly. $\endgroup$ – IT Alex Aug 28 '19 at 18:09

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