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You know the old saying

A slow or fast running watch is worse than a stopped (broken) watch. At least the stopped watch shows correct time twice a day!

Here is a challenge:

A person was wearing a stopped (broken) analog wrist watch with hour, minute and second hand, that also displayed the date ( Monday thru Sunday and the day of the month) which showed correct time and day at least 5 times during a continuous 15 hour period.

The person did not touch the watch settings. He was on the ground all this time.

How is this possible?

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How is this possible?

Let's suppose you are in a country which observes Daylight Savings Time and border a country which also observes it and is in a time zone which is one hour behind, then you can observe the exact time twice during the clock change and then cross the border to observe it a third time. Cross back and observe the time once more (in 11 hours) in the first country and cross once more to observe the time in the second country.

If all that is confusing, here is an example

Suppose that you are in Ukraine near the border with Poland on Sunday, 27th October, 2019 at 3:30am and your analog watch has stopped with this date and time. This is the first observation.

In 30 minutes, the time in Ukraine "goes back" from 4am to 3am and one hour after the first observation, it is 3:30am again in the Ukraine. This is the second observation.

Next, you cross the border to Poland where the time is 2:30am. Wait for one more hour and your watch is right again, for the third time.

Next, cross back to the Ukraine where the local time will be 4:30am. Wait for 11 hours until the time becomes 3:30pm. Your analog watch doesn't distinguish am/pm so, again, it shows the right date and time, a fourth correct observation.

Finally, cross back to Poland, where the time will be 2:30pm. Wait for one hour and the time will be 3:30pm, making it the fifth occasion where your analog watch will be right, and all within 15 hours.

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  • $\begingroup$ Hfvat Vagreangvbany Qngr yvar naq nyybjvat sylvat, pna guvf unccra 6 gvzrf be zber? $\endgroup$ – DrD Sep 15 '20 at 12:24
  • $\begingroup$ @DrD jryy, erzrzore, lbh'ir chg gur yvzvg bs 15 ubhef fb gur Vagreangvbany Qngr Yvar pna bayl cebivqr fb zhpu uryc, ohg jvgu sylvat lbh pbhyq cebonoyl trg hc gb 15/16. $\endgroup$ – hexomino Sep 15 '20 at 12:28
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    $\begingroup$ Wow. Never thought a stopped watch could be that useful :) $\endgroup$ – DrD Sep 15 '20 at 12:29
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    $\begingroup$ And just think, if you had a running watch, the watch would be right a maximum of twice...and far more likely, zero times! $\endgroup$ – Exal Sep 16 '20 at 8:55
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    $\begingroup$ @Stormblessed not sure if you were referring to my " Never thought a stopped watch could be that useful :) " comment. It went back to hexomino's ansswer in rot 13 to my question. Under certain condition -- using International Date Line the stopped watch might even show correct time many more times $\endgroup$ – DrD Sep 16 '20 at 10:05
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Since @hexomino's brilliant answer requires that the clock is stuck on a particular time on a particular date, here's another:

On the day that your clock is stuck on,

find any point where three (or more) time zones meet.

Some suitable candidates (there are many more, try to pick one where you're least likely to get shot at):

The three-country border point between
- South Sudan, DR Congo, and Central Africa
- Norway, Finland, and Russia
- Iran, Afghanistan, and Pakistan
- Belarus, Lithuania, and Poland

* The North Pole (probably doesn't count as "on ground", though)
* The South Pole (might get a bit chilly, so it's good you only have to wait 4 hours here.)

Apart from the last two possibilities, in (or very near) these places a stopped wrist watch will be correct

three times before noon, and three times after it.

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    $\begingroup$ The curiosities of time zones continue to amaze! +1 $\endgroup$ – hexomino Sep 15 '20 at 14:44
  • $\begingroup$ There are places in US (Columbus GA at the border of GA and Alabama, where 2 time zones meet on a street (3rd and 4th). So literally you can have one foot in EST and the other in the CST. Other fact is that Times in US change at 2 AM Sunday all across. So there is that one Common hour between neighboring time zones $\endgroup$ – DrD Sep 15 '20 at 15:21
  • $\begingroup$ Very logical @Bass. I did not think of all those options. $\endgroup$ – DrD Sep 15 '20 at 19:10
  • $\begingroup$ Nine times if all of those countries also change their clocks for daylight savings! $\endgroup$ – user253751 Sep 16 '20 at 17:56
  • $\begingroup$ There are apparently places in Russia where three time zones meet. $\endgroup$ – Max Xiong Sep 17 '20 at 3:57
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Another possible answer.

The question stipulates that "A person was wearing a stopped ... watch" and that "He was on the ground all this time." The question makes no stipulation as to if he was wearing the watch for the entire 15 hour window. Since the watch was not necessarily on the person the whole time, the watch itself could have been in the air for at least part of the time. The watch broke in the AM and your person then took it off to ship it back to the manufacturer for repair. Of course it takes time to package and ship the watch so it does not actually make it onto the airplane and into the air until about 12 hours after it broke. This gives you 2 correct times in the first time zone. The plane then crosses into 3 other timezones as it flies making it correct 1 more time in each one.

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    $\begingroup$ In the question it says that "A person was wearing a ... watch". Therefore if he is on the ground, so is the watch. $\endgroup$ – bobble Sep 16 '20 at 18:24
  • $\begingroup$ @bobble Keyword "was". If you read this question carefully, it neither confirms nor denies if he he was wearing the watch for the entire 15 hours, just that he was wearing a broken watch at some time in the past and that it was broken. $\endgroup$ – Nosajimiki Sep 16 '20 at 19:28
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    $\begingroup$ The entire question is in the past tense ("displayed", "showed"), so the "was" can be inferred to refer to the same timeline as the rest of the statement. More importantly, this question isn't tagged [lateral-thinking]. The intent of the puzzle is clear, and the better answers here work within that intent. $\endgroup$ – bobble Sep 16 '20 at 19:33
  • $\begingroup$ Some people are such killjoys :) $\endgroup$ – Caius Jard Sep 17 '20 at 10:20

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