I actually had been thinking of posting a groundhogs day question the same day that Tomorrow is Groundhog Day... For everyone. How does society respond? was first posted ironically, it's a sign!

In my scenario assume someone was thrust into your standard groundhog day loop, repeating a single day over and over. They are an average joe, or perhaps a little smarter and better off then average (say upper-middle class), but not rich or possessing of special traits or skills, and they had not planned to start the groundhog day loop before it happened. They have determined the cause of the groundhogs day loop and now believe they could stop it on any day. Once they exit the loop they will never be able to re-enter a new one.

So, how does one exploit the loop they are in before ending it? Specifically say that this person's primary goals are to help others. He is not a saint, and would appreciate and do anything to improve his own quality of life (and I'm interested in approaches he can take here), but he is mostly interested in helping others by using this unique opportunity.

He has the advantage that he can choose which day he exits the loop near the end of the day. Thus he can try for a 'perfect' day and if something does work out keep repeating until it does before exiting.

Now lets apply a few limitations

  1. He is pragmatic and willing to bend a few rules for the sake of the greater good, but he is still restricted by moral views. He does not want to lie or manipulate others (using his 'psychic' future predicting powers) unless there is a major and immediate good.
  2. He is not certain what happens if he dies, but he is not guaranteed to come back to life next loop. Thus he is not going to take any absurd risks
  3. He will not repeat an infinite number of loops. The constant repeating of the same day without progress can grow repetitive and eventually drive one insane if done enough. In addition he is worried about 'forgetting' seemingly silly things. He may have seen someone chronologically 2 days ago; but after 50 subjective years of groundhogs day repeating he could forget the face of his own girlfriend he saw 'yesterday' etc. Thus he can not an will not repeat forever to master every skill in the world etc. He is willing to do many repeats, and in fact could experience subjective years, but only so long as he feels he is making clear progress. Any idea that takes many subjective years to work towards should include things he can do to help him feel like he is making progress and keep sane through the efforts.
  4. He has an average to slightly below-average memory. He will be limited on how many facts he can remember each day, unless he spends a good amount of time training himself to memorize those facts and repeating them to himself every few days to reconfirm them.
  5. He would prefer to go back to a normal life after this is all over if possible. He does not particularly want publicity and, while willing to tolerate it, particularly in the short term, does not want to be some media sensation. He would prefer to find approaches that don't draw long term attention, and particularly avoid doing anything that can't be explained by him being at the right place or dumb luck, if he can avoid it. He is, however, willing to draw more attention if it does enough good to justify it.
  6. He is no older then 30, with decent savings and is a quick learner, but is not a genius, has no super powered friends, and generally is not going to be able to call in favors or use any political power to make something happen on a given day. I don't care what his job is, so it's acceptable to suggest he has a job or skill that would be useful so long it's not a particular rare job/skill and a 'normal' person could be expected to have it.

The original groundhogs day suggested doing small things around your town, by finding out exactly where you had to be to be at the right place at the right time. I don't think this was looking far enough. With the ability to know practically anything about the world you want a day in advance, enough time to plan out and even try multiple options before picking the right one, and the ability to retry crazy one-in-a-dozen potential outcomes until they work out surely a far larger amount of good could be done. Were not limited to local good either, improving the lives of some stranger in China is just as good as that of his neighbor if he can do it.

What are some viable options to exploit the groundhogs day loop to improve quality of life?

I'll throw out one option now, win the lottery. He can win one, or multiple lotteries at the end of the loop, perhaps even plan out which to win to get the most money with the least attention. Maybe he buys scratch off cards that he has determined are winners (from trial and error) all on one day and cashes them in over years so as not to draw as much attention. He could also take all his money and gamble it at a casino in an all-or-nothing gamble and keep trying till he doubles or quadruples his money.

This money could then all be donated to efficient charities. He would be 'stealing' the money from those who would win it, but he will use it to do more good then the other winners would.

He could also try to find disasters he can warn others about to avoid them happening. No 9/11 or Chernobyl style disasters occur on that day; but surely some smaller disasters would occur around the world ever day. With time perhaps he could find out many of these 'smaller' disasters, where 'only' a few dozen to a few hundred die, and figure out who to call in an anonymous warning to in order to avoid them? Though I'm not sure how he would find any that aren't reported on his local news?

What other ways can he make large scale improvements, or small scale improvements with minimal effort (so he can do many at once).

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    $\begingroup$ I'm calling this too broad. Have you ever seen a domino display? Taking a small action today can have momentous consequences tomorrow. There is no way to know the best course of action to take for a better future unless one can see the future change in real time. If you save a child today and he grows up to be a mass murderer, did you do a good thing? $\endgroup$
    – Frostfyre
    Commented May 29, 2015 at 16:39
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    $\begingroup$ I think the bigger problem with this question is that it really depends on the day, and where the guy is for that day. There are so many options, but each of them has a lot of variables. $\endgroup$ Commented May 29, 2015 at 17:22
  • $\begingroup$ I presume "remember the winning lottery numbers" (and other related "insider trading" gambits) are either assumed or precluded? (Depending on whether starting your new life filthy rich is considered good or not.) $\endgroup$ Commented Jun 4, 2015 at 19:06
  • $\begingroup$ @AllenGould winning lottery was presumed, though limited by a desire to not get arrested for apparent lottery fraud when he wins ALL THE LOTTERIES! Other insider trading tricks that could allow quick gain of money without drawing too blantant of attention, or at least not enough to suspect fraud, are welcome; so long as their not exploitative. Any money he gains through these tricks 'steals' it from others who would have gotten it. He's willing to do so at a point, since he can do more good with it in the lottery, but no crashing the stock market or other things that really hurt others. $\endgroup$
    – dsollen
    Commented Jun 4, 2015 at 20:06

6 Answers 6



Which is not to say that there's any point in him going out and stopping crimes that day. But what he can do is use travel, phones, and computers to ferret out information on criminals and set them up to be taken down in the future.

He can basically hack his way into anything, and his huge advantage is he doesn't care if he gets caught. That's just more data for him to work with the next day. Whether it's technical hacking on a computer, or social engineering, the fact that he can try things without worrying about the consequences is a huge benefit.

So what he should do is use those techniques to find evidence of crimes on as many people as he can remember. Then when he exits the loop, he can expose that to the FBI or whatnot. He should be able to take down or significantly hurt mob bosses, white-collar criminals, drug runners, etc. Maybe even terrorists, or people currently hiding who are guilty of war crimes, things like that.

  • $\begingroup$ Why does ground hog day ability = hack into anything? Most systems are secure even against attackers who don't care if then get caught. He can't accumulate evidence so criminals could be arrested since it all vanishes at the end of the day. He can only tell the FBI about who he suspects. $\endgroup$ Commented Mar 17, 2016 at 17:09
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    $\begingroup$ Imagine a nobody walking in to the FBI and explaining detailed information about their top-10 hit list. I think he'd have a hard time explaining himself. $\endgroup$
    – Mirror318
    Commented Jun 9, 2016 at 4:44
  • $\begingroup$ @sdrawkcabdear Because with unlimited time he can essentially brute force his way past any security system. Granted, this still might take more time than dsollen might want (e.g. thousand, millions or even billions of years) but in reality it's probably closer to the case of learning one correct digit of a password at a time - far faster than brute forcing. On any give day he can probably manage to get one piece of information which, by itself nobody will think twice about losing (and if they do, so what if he gets captured to get it) but put enough of them together... $\endgroup$
    – Michael
    Commented Sep 21, 2016 at 23:09
  • $\begingroup$ @Michael point 3 says "He will not repeat an infinite number of loops" the author implicitly limits this to 50 years of retries. This could get you into a number of systems but all systems seems unlikely. $\endgroup$ Commented Sep 22, 2016 at 0:25

Actually, this is not really too broad a question as the solution is actually the same regardless of circumstances, only the details differ. This is because in this kind of loop the changes you can affect in the world are limited by the time, one day, which is generally small compared to your overall lifespan. In contrast the changes you can affect on yourself are generally much larger as the information and skills you learn in one loop usually remain.

Thus the best use you can make of this is to study anything you have any interest in. The study might involve experimentation needed to build some invention or physical exercise. It specifically includes studying yourself. That takes time and reflection. A time loop is the ideal place for it.

And then after you get bored with that use the advance knowledge of the day to break the loop and do some manipulation. You could of course use that advance knowledge to make lots of money, but it is generally better not to optimize too much on things that are not hidden inside your head.

A person who has studied quantum physics "on his free time" is weird and unusual, a person who makes a bunch of highly profitable investments in a short time is subject to visits by people who check in their sense of humour when they arrive at work. It would look pretty much like insider trading or money laundering from outside. The same is true for most other get rich schemes.

So just use the nearly infinite time at your disposal to make yourself the best person you can be and then move on with your life. For example if you wish to help other people, become someone who can and then, after the loop ends, go do it.

  • $\begingroup$ I would argue that there are plenty of one-off methods to acquire a lot of money using foreknowledge without excessive scrutiny - for instance, winning a large jackpot lottery once would attract no more attention than any other winner gets. $\endgroup$
    – Michael
    Commented Sep 21, 2016 at 23:12
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    $\begingroup$ @Michael No argument there. The key term here is "one off". My point wasn't really that you can't make lots of money, just that the amount of effort you can put to it without issues is limited, so that most of your in-loop time and effort should go elsewhere, Making money falls squarely under the category of last loop manipulations, really. $\endgroup$ Commented Sep 25, 2016 at 14:18

Wonderful question! I have a few of my own:

Does the person have a strong sense of calling in their life?

People with a strong sense of calling - pastor, missionary, doctor, environmentalist, social justice advocate - will have the easiest time of it. They can perfect knowledge in their area of pursuit. Take pastor for example. The person might not have the time and money to attend seminary. Now they can study Greek, Hebrew, theology, pastoral counseling, etc and try out what they learn on the people around them. As for using the information they learn like a "psychic", they would of course interpret the Groundhog day thing as a miracle and assume all the knowledge they learn about other people is a gift from God that can be used to persuade others that God exists and loves them.

However people without a strong sense of calling (like the Bill Murray character, who hated his job) will have to go through more trial and error. Such a person could become almost anything, but their temperament, likes and dislikes will steer them toward something that interests them. That is why self-understanding is the most important first goal.

Does the effect of exercise or physical activity persist?

Can a person become ready for a marathon? The Bill Murray character learned how to play piano. This required conditioning his hands and fingers, not just learning theory. So how much physical training can they engage in that will persist across the days? This will limit which activities are beneficial.

Cyber Security!

With perseverance, one could break into most computer systems in the world from a public terminal. One could learn these skills and obtain information from our nation's enemies, organized crime syndicates, corrupt politicians, etc, then anonymously release it to the right places to maximize the benefit to law and order, international peace, etc.

Find Missing Persons

You could perform an exhaustive search within several hours' travel radius and find all kidnapped people, enslaved immigrants, drug factories, etc. To avoid personal danger, you call in tips and study the police response to see if any criminals were found. This would yield one significant, one time benefit.

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    $\begingroup$ Most cyber security systems are designed to be resistant to several hundred years of brute force attacks. You would go insane/forget everything you knew before you could crack it. Lets face it you could relive the same day for only 50 or 60 years before going totally crazy and a good crypto system would still be locked. $\endgroup$ Commented Mar 17, 2016 at 17:19
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    $\begingroup$ @sdrawkcabdear two words... "social engineering" $\endgroup$
    – Michael
    Commented Sep 21, 2016 at 23:14
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    $\begingroup$ @Michael What if the target takes more than a day to respond to his email? What about air gapped systems? $\endgroup$ Commented Sep 22, 2016 at 0:27
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    $\begingroup$ @sdrawkcabdear I assume he'll just go to the person's office. One day he'll be the A/C guy to fix the cooling (because he learned the previous loop that the AC needed to be fixed, and intercepted the real cooling guy). The next day he'll be the temp filling in for the secretary that called in sick because he secretly won a free vacation in her name... $\endgroup$
    – Michael
    Commented Sep 22, 2016 at 1:12
  • $\begingroup$ @Michael that works for offices near his starting position, that are open on his ground hog day. Requiring you to physically access the place is a huge limit to the set of systems accessible. Its still a big help $\endgroup$ Commented Sep 22, 2016 at 1:20

Call the local high school physics teacher and convince them of what's going on. Have them contact the closest quantum physicists and convince them as well. Have them organize a global internet forum of world-class quantum physicists to discuss the opportunity. Have each forum attendee provide one intimate secret which the looper can memorize, streamlining the process of gathering forum participants during subsequent loops.

"Hi Mr. Kaku, Thank you for speaking to me. I am a time traveler and as proof of that claim, later today, you will tell me that your mother's eyes were green.
Please call the following conference phone number to join the discussion. Bye."

Time loops are extremely rare. As far as any of us know, none have occurred since the birth of science. Giving the task of optimizing a timeloop opportunity to the strongest minds on the planet, is the best way to maximize its positive effect. The tests they would devise and have the looper perform at the end of each passing iteration, would illuminate the otherwise unperceivable nature of time, allowing our science to advance dramatically.

Yes... I stole this answer from Stargate, but they stole it from Bill Murray, so...

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    $\begingroup$ After reading this answer, I like to wonder if the asker of the question is in a time loop. I actually thought up the same thing but decide against it because I thought if people believed it then they might kill the guy or make him break the time loop. Though asking the question on this and similar sites online would be a better answer as no one would believe him anyways. $\endgroup$
    – Necessity
    Commented May 29, 2015 at 20:49
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    $\begingroup$ Adam Nicholis... +1 Great Thought! @dsollen... During your next iteration through today, could you please add a comment to one of my posts listing tonight's winning lotto numbers! I'll split the winnings with you tomorrow! $\endgroup$ Commented May 29, 2015 at 20:56
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    $\begingroup$ @AdamNicholls The asker of this question had thought the first thing he would do in a timeloop is post a question like this.. Rather he thought of this while in a timeloop or not is undisclosed. In other news it's been more then a day since this was asked, the Daleks haven't invade and the TARDIS was not harnessed in an attempt to gain ultimate power that backfired when an innocent, but handsome, civilian wandered too close and set of the quantum compactor too soon. Not saying that is at all relevant but...just saying anyone who stopped that must be pretty brilliant and amazing right? $\endgroup$
    – dsollen
    Commented Jun 1, 2015 at 14:38
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    $\begingroup$ @dsollen Well, yeah, obviously (maybe) $\endgroup$
    – Necessity
    Commented Jun 1, 2015 at 14:51
  • $\begingroup$ I don't think 24 hours is enough time for this to work setting up such a conference would simply eat too much of your day. A better option would be to learning the physics yourself, then get a theory for time loops in place, and then contacting a professor at your closest university. Also I would not go by "you will tell me that your mothers eyes are green" - he might believe that I got the color from some other place, I would go with "your SSN is...", and just keep guessing until I got an answer that was accepted. $\endgroup$
    – Taemyr
    Commented Aug 27, 2015 at 12:24

Blockchain your way to victory.

Do insider-trading/fortunetelling on anything that will get you money before the day is out. Stock-trading sometimes has 3-day limits on getting you the proceeds, so that may be out. It might be scratchers lottery tickets at $600 a pop.

Get the money as soon as possible during the day, and start purchasing computing power to do blockchains on cryptocurrency. Digits are small, and worth memorizing.

As soon as you have enough in cryptocurrency, the next day you can start spending that to buy computing power, to make further gains in the blockchains. You can also start making that money and renting machines and such, virtually, and at any point in the day (12:05:AM, then roll over and go back to sleep)

Money will help you do the other things that you need to get done.

Get the smartest people to help

Similar to @HenryTaylor's answer (but not quantum physicists). ie: Get the smartest people in the world to help you figure out what could/should be done (Gee, what's this site doing?). Not a problem for personal safety, you have a good escape and evasion plan (or start a separate forum for increasing your skills in that) that only needs to take you long enough to reach the reset point (ie: go to bed early). Then you only add one or two people a day to the forum. If someone starts hunting you that day, you likely know who the problem was, and/or can stop at the prior level of involvement and start investigating who was hunting you, and how the interaction between prior involved people was causing this to happen. In any case, when you select your exit-day, obviously you don't set up a forum that day, and none of them know that they helped you.

Btw, mother's eye color and SSN are particularly bad questions for this. Either is learnable by thorough investigation of a target. If someone called you up out of the blue and told you they knew your mother's eye color, would you conclude that they're a time-traveler, or would you suspect a prank or someone who knew you/your mom?

I'd call them on their personal unlisted phone number, at 1:AM; and (on first iteration: ask them to write down what they're thinking/pick a random word or phrase/number), then tell them that (on the next iteration). Might be best to use a text-to-speech application, to prevent tone, inflection and spacing of the words from causing any unforeseen variation in their selection of something random. Anyone who lies, can be told they're thinking of lying the first time, and to do it correctly.

Get EVERYONE to help

If you want the whole world to work on the problem of what's most useful to do, you can release information on future micro-quakes publicly, then alert reporters who you've dug up personal information/blackmail on to report widely. Then you can get started by brain-storming on a wikipedia page (or some high-traffic site; blackmail a google executive into hosting, if they don't believe). You could also pay each reporter to go purchase scratchers tickets from a location (on first iteration) until you tell them how many tickets down they need to go, and in what pattern to scratch to pull in actual money - if you want a surefire way to get a lot of publicity.

You can also work on winnowing down to the most useful/connected people you need to reach first. Who can convince the most with the least effort. Then you can spend less time on convincing people and more time on memorizing the things that need to be memorized.

You might want to convince George Soros or Bill Gates. Call them up on their private phones. Then maybe providing them some stock market data, and convincing them to give you passwords to one of their existing (or just created) portfolios. Then tell them to spend a billion dollars and get some shi...stuff moving.

The problem with big lotteries

Winning a big lottery is going to be a problem - they typically don't hand you the cash the same day (numbers are often pulled after working hours/there's still paperwork to do). So you're not going to be able to know which ones are going to get you investigated and which ones are not, or what the threshold of "winning too many" is (consequences may take days to manifest). You also have the problem of getting the tickets purchased (time/space constraints); but taskrabbit and the like make this much easier. Of course that may ruin your non-publicity status, as if more than one taskrabbit publicly comments that they purchased a winning lottery ticket for an anonymous someone in [place]... a reporter might take note of it. Have you tried to buy a lottery ticket from Europe? Or from a state or two away on the other side of the Mississippi?

Actual suggestions

Of course, those are some smart ways of doing the actual thing. Writing some fiction means that your protagonist is going to end up with some actual suggestions, which you're going to need.... here's some:

Once you've got money, you can also post hacker-challenges: Find a bug within 12-20 hours, and win a million bitcoin. Done right after you release all the bug-fixes from the prior iteration.

Any task-intensive search project: Have each researcher break it up into one day search chunks, and then tell them which day they should search on for each iteration (which will also help you keep sane, and track of how many days you've spent doing shit). All you need to do is remember which day the successful solution was found on for each project. Conversely, you can even prevent local optimum solutions, and find global optimum solutions by traversing the whole search-space, even if you find a pretty good candidate early on. Say, SETI or astronomical searches. Gene therapy research.


The easiest way to do good is with giant piles of cash. Memorize every horse race, every match, every game, every lottery that happens that day. Practice setting up all the accounts you need as fast as possible. Many of them pay out fast. Dump all of your savings into every chained-bet possible, particularly the long odds bets or ones with jackpots.

Sure, it will probably be noticed but there's no explicit laws against time travel.

End the loop and dump your tens of millions of dollars into the most effective charities you can find. (remember, the marginal cost of saving a human life is between \$1000 and \$4000 so you can save far more lives than the character in groundhog day)

Pay any taxes due, move somewhere out of the way and pay an actor to pretend to be you if anyone from the media comes looking for "that guy who won all that money".


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