Pennyless Joe, the broke archeologist, finds an old pawn shop selling something curious. A ceramic vial labeled "Groundhog Day Potion". It's a bargain for $1.99. (He buys it, because he is not quite that broke).

Pennyless Joe is very intelligent (though not financially savvy) and well versed in archeology and alchemy.

After buying and studying the potion sample, he learns that the potion is real, still potent and allows the imbiber to "Groundhog" - relive an entire day with full memory of what happened on the first iteration of that day, but you only relive the day a single time.

He also knows there is no way to duplicate the potion, because it requires a long-extinct herb and the magic in the potion will be spent at the start of the replayed-upon day.

But alas, by breaking the seal, the millennia old potion begins to lose potency. Pennyless Joe's alchemical knowledge tells him that the potion will only be useful by December 24th of 2016.

So Penniless Joe wants to use the potion to reverse his wealth predicament, and make the most cash out of this single day.

what should his winning strategy be for this one day, to get really rich?


This does not break or invalidate any answer already posted at the time of this edit so:

Penniless Joe does not have much money on him after buying the $1.99 potion. He does have an income, but it barely meets his monthly expenses.

You can make any assumptions about his credit rating or any other ease/hardness of obtaining credit.

Also keep in mind that he has one year to use the potion.

P.S.: please do not answer with some potion-duplicating infinite loophole. It is intended to be a single-use artifact.

  • 1
    $\begingroup$ Does the answer have to be a morally good one? $\endgroup$ Commented Dec 23, 2015 at 16:45
  • 2
    $\begingroup$ @ScottDowney Pennyless Joe is desperate. Anything goes as long as the world still remains there and his chance of being caught is low. $\endgroup$ Commented Dec 23, 2015 at 16:56
  • $\begingroup$ I'm guessing you don't have anything like Euromillions rollovers where you are, you don't even need a full day, just a couple of hours and you can be sitting with £160Million tax free at the top end. That classes as really rich by almost anyone's standards. $\endgroup$
    – Separatrix
    Commented Dec 24, 2015 at 10:02
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    $\begingroup$ To make the back story more believable, Joe could have two vials. He drinks one (for what ever reason) ground hogs, but finds the first vial(drunk) is the only thing out of place. The next day is a non-groundhog day, where Joe realizes how it all works and is about to pop the second vial to do another groundhog trip, when he checks himself and starts to plan things properly. Joe could have some other hard deadline that he needs to get things sorted by(child coming home, xmas with child, owing money, mortgage repayment holiday coming to an end etc) $\endgroup$ Commented May 25, 2016 at 5:41
  • $\begingroup$ If he's so well-versed in alchemy, why is he so penniless? Why does he not just get rich by turning iron into gold? $\endgroup$
    – komodosp
    Commented Aug 27, 2019 at 7:49

6 Answers 6


With only a single day's knowledge, and a single chance to exploit this day's knowledge, the correct answer would almost certainly be lottery tickets.

There are few - if any - ways to make a short term 'profit' on a par with gambling, and knowing the day's lottery numbers is the only way that would really be possible for an individual to accomplish in the repeat of a single day. Many iterations may allow more theoretically profitable opportunities (such as repeated wins at casino games), but Joe would only need to memorize a single sequence of numbers to win the lottery - something completely doable in a single day.

Ideally, Joe would play and win the lottery multiple times in a day (Pick-4 in the afternoon, reinvest in bigger payouts later) but the fixed maximum payouts on a single lottery would probably limit the value of that strategy unless Joe could play multiple different lotteries all at once.

Of course, if Joe's trying to accomplish this without attracting any attention (once the day ends and he's back on regular time), simply playing the single largest lottery once would be the way to go.

  • $\begingroup$ There is no reason not to play multiple state's lotteries. $\endgroup$ Commented Dec 23, 2015 at 16:57
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    $\begingroup$ @WhatRoughBeast Avoiding attention and suspicion would be a good reason. $\endgroup$
    – Avernium
    Commented Dec 23, 2015 at 16:59
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    $\begingroup$ @Avernium People have won multiple lotteries before I don't see why this would attract any dangerous attention. $\endgroup$ Commented Dec 23, 2015 at 18:21
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    $\begingroup$ @WhatRoughBeast Multiple state lotteries would require a lot of travel. Joe's near penniless and can't afford it. Note that state lotteries are almost universally smaller than the two multistate lotteries. Since he only has one day, he can only win one multistate lottery (they draw on different days). He'd play the Powerball today (Mega Millions doesn't pick until Friday). Of course, this assumes that the lottery picks would be the same on both iterations of the day. They might well be different. $\endgroup$
    – Brythan
    Commented Dec 23, 2015 at 18:26
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    $\begingroup$ All it takes is a family member with a different last name or a good friend in another state. Tell them, buy this number and I'll explain why tomorrow - and don't tell anyone I told you. Though ultimately I think you'll get a bigger haul if you wait for a single, big multi-state lottery drawing. $\endgroup$ Commented Dec 23, 2015 at 21:43

Joe must locate wealthy individuals with terminally ill or dying relatives, offering 'one more day' in exchange for the personal wealth of the individual.

Joe may not be able to look at himself in the eye ever again but a mansion doesn't really need mirrors, does it?

Simply ensure the paperwork is in place the day before delivery of the potion - so the recipient re-lives the next day.

  • 2
    $\begingroup$ He'd have better luck asking for 50%, after the wealthy individual uses their operating capital to double their money during the repeated day. $\endgroup$
    – Wingman4l7
    Commented Dec 23, 2015 at 17:36

Getting away from the normal kind of gambling, he should short sell stock.
Find a few stocks that have massive daily losses at the close of the market.
On the loop day sell the stocks short.
Cover the shorts as soon as the market reopens after loop day.

This has a benefit over buying stock because you need to have money to buy the stock, which Joe probably doesn't.

This has a benefit over the lottery because there might not be a mega millions lottery on the day he happens to open the vial.

Make sure you pay your taxes.

How to convince a friend that invests that you're not full of crap:
On the 22nd talk to a friend and have him choose between 3 and 5 stocks, write down the ticker symbols, but not tell you what they are, with the understanding that you'll either call him at 7 in the morning to tell him the exact price the unknown stocks he chose will be at 11 am, or that you'll call him at 11 am to find out what the ticker symbols are.
On the 23rd (first pass) wait till 11 am and call for the ticker symbols. Write down the prices for those symbols. Then wait for the close of the market to see who you should short. Maybe consult with your friend to get some input on what ones are the best.
On the 23rd (second pass) call your friend at 7 am and tell him which stocks he chose, and what the prices are going to be. At 11 am call him and tell him which stocks to short.
On the 24th close the trade and split the profits with your friend to the agreed upon amount.

  • 2
    $\begingroup$ I was going to give this answer, but then I realized he's Pennyless Joe -- he doesn't have the capital to make the initial trade. Unless he's naked short-selling? $\endgroup$
    – Wingman4l7
    Commented Dec 23, 2015 at 17:57
  • $\begingroup$ From my somewhat limited knowledge of stocks and a little light reading, you technically don't have to have any money to short a stock, you just have to have someone who will loan you a stock to short, and then cover it when you close the trade. If Joe is having trouble finding a broker that will work with him, he may have a friend or relative that he can bring into the deal. With 1 day to plan before loop day, he should easily be able to convince someone that he's not full of crap. $\endgroup$
    – AndyD273
    Commented Dec 23, 2015 at 18:22
  • $\begingroup$ Good edit; I'm beginning to be convinced that the most realistic solution for success involves a promise to split the profits with whoever is willing to risk investment. $\endgroup$
    – Wingman4l7
    Commented Dec 23, 2015 at 22:06
  • $\begingroup$ The trouble with stock trading is that the act of trading can affect the outcome. Joe finds a stock that has a declining price in pre-loop time, borrows some of that stock and tries to sell it in groundhog-loop time, however there are two potential problems: No-one wants to buy that much of that stock at Joe's asking price, and/or because other people are watching the stock market too, they notice the unusually large movement of stock and the price goes up instead of down, and Joe is too penniless to cover the cost of rebuying the stock at the higher price. $\endgroup$
    – Monty Wild
    Commented May 23, 2016 at 23:54
  • $\begingroup$ @MontyWild I don't do much stock trading, so you probably know more than me, but without someone actively trying to screw with him it seems like he'd probably be ok if he's smart about it, and especially if he works with an experienced trader. The danger could be minimized by spreading it out over a few stocks, making the blocks smaller so it would affect the stock less and make it easier to sell. $\endgroup$
    – AndyD273
    Commented May 25, 2016 at 15:42

The best plan for maximizing your wealth in a single day involves the following.

Pre Planning Steps (not in any particular order)

  1. Pick a very busy day in sports, in the United States this will likely fall sometime in Autumn when you have professional and college football, professional baseball, professional basketball, hockey...etc.

  2. Take out a large reverse mortgage on penniless Joe's home

  3. Travel to Vegas. Spend the very busy sports day documenting all the games being played. (it would help if you can carry over a notebook from one day to the next, but if not he could get the scores and stuff tattooed on himself).

  4. Spend some time with a few high rollers in the casino and keep track of their day to convince them on the repeat day you can make them a lot of money if they invest in your day.

  5. Find a stockbroker in Vegas for ease of access when you choose to repeat the day. Again, make sure they know you, call them and see what things happened during their day so the next day you can more easily convince them to maximize your time/money.

Repeat Day

  1. Get up really early, meet with the whales and call your stockbroker to get them in on the plan. Take your mortgage money and any cash from the whales and invest in the market based on what you know you can make, waiting for a day where there were big changes will obviously make you more money.

  2. Use some of the money to hit sports books around vegas and spread your winning bets around (no one wants to get broken bones by making a casino think you are cheating) bet big obviously the crappier the odds the larger the bet...putting it all on one bad bet you know will come through is efficient but...spreading things around should draw less attention...until tax time at least.

  3. Enjoy the day, have some drinks, gamble (though I should mention that gambling won't be certain since you are likely creating an alternate reality by gaming at table...where you change the dynamic as opposed to sports and lotto betting)

  4. Bet the lotto...obviously. Wait for a large jackpot that no one else wins (no one wants to share a jackpot afterall)

  5. Hire a wealth manager

  6. Profit...

  7. Visits from the NSA, FBI, IRS, and other agencies who are going to be very very suspicious...


Joe thinks about lottery or casino first, but he is intelligent and he has read about the chaos theory before and he has a nagging suspicion that not just a butterfly might flap her wings differently, but the mere breathing differently might cause variations in thermal noise of the lottery machine, and it's quite probably the numbers will be different the second time (and it's almost guaranteed with the roulette, especially the electronic kind that draws randomness from quantum noise). Oh, he will buy a few tickets, just in case.

OTOH, stock markets (or even better forex), are less random, more dependent on general trends. So he will spend the time familiarizing himself with the forex operations and then put everything into the financial operations. Unfortunately, being penniless, the most he would be able to invest is his monthly salary (just after he receives the cheque).

The exact nature of the potion is important - if he drinks it, will he relive the previous day until the drinking, or the following one? In the first case, he might wait for some unexpected big changes in stock market or foreign currency like this one. Unfortunately, he'll never know if there's not something better tomorrow, but if he waits for too long he might never get better opportunity.

  • $\begingroup$ He relives the day he drinks. so the best strategy for predictions is to wait until almost midnight. $\endgroup$ Commented Dec 28, 2015 at 2:13
  • $\begingroup$ @Mindwin Does the potion recognise time zones? In that case, it makes sense to be as much as possible eastwards in the morning (or just after midnight) of the groundhod day and then travel westwards, or even better cross the international date line into the previous day (but that might be more difficult to arrange with little money). Fortunately, he can do all his stock market observations remotely and crossing time zones requires just to buy a plane ticket. $\endgroup$ Commented Jan 1, 2016 at 19:02
  • $\begingroup$ Radovan: Let's invoke the "Gremlins rule of when it is not-after-midnight" on this one. Warning:tvTropes $\endgroup$ Commented Jan 4, 2016 at 12:26


Go to a casino, note the numbers that come up. Go back, spread your bets around enough that it's not so obvious that you're making a mint. Continue until the casino throws you out.

  • 2
    $\begingroup$ I feel like this kind of gambling runs into causality/alternate reality issues...by gambling you alter the outcome of future gambling events as you personally impact what is happening at the time (as opposed to lotto or sports betting) $\endgroup$
    – James
    Commented Dec 23, 2015 at 22:05
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    $\begingroup$ Joe would unable to replicate his behaviour perfectly and as such his turning up at the table differently would affect how the dealers actions occur. Nice idea though. $\endgroup$
    – Prinsig
    Commented Dec 31, 2015 at 11:28

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