My twin and I constantly argue about who is the elder. He claims that just because he was born first, he is older than I am. I refute his claim and point at our birth certificates, which clearly show that I am older. Our mother says it doesn't matter since we have the same birthday and tells us to stop bickering!

We're both telling the truth, but how can this be?

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    $\begingroup$ Possible duplicate of Older twin's birthday is one day after younger's $\endgroup$ – Rand al'Thor Dec 11 '16 at 12:32
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    $\begingroup$ @randal'thor, not a duplicate. I've edited to add an extra clause so that the answer is different. $\endgroup$ – James Webster Dec 11 '16 at 12:35
  • $\begingroup$ OK, close vote retracted. $\endgroup$ – Rand al'Thor Dec 11 '16 at 12:37
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    $\begingroup$ Your legal name is "older", with a lowercase O. $\endgroup$ – Tanner Swett Dec 11 '16 at 19:04
  • $\begingroup$ I'm afraid not Tanner, my legal name is the same as my screen name. $\endgroup$ – James Webster Dec 11 '16 at 19:38

Similar to a recent puzzle,

You were born on a day when Daylight Savings Time ends, rolling the clock back one hour. If your twin is born just before the rollback time, 2am for the US, and you are born just after it, then your birth time is shortly after 1am and your twin's is shortly before 2am.

The recent puzzle: Missed Appointment, no doubt the inspiration for this one.
See comment below from OP for the actual inspiration!

  • $\begingroup$ This is the answer I was thinking of. However, the inspiration is actually this story $\endgroup$ – James Webster Dec 11 '16 at 12:39
  • $\begingroup$ @JamesWebster Wow! I mean, with enough births happening I suppose this is inevitable, but I didn't really think this was an actual thing :) Very nice! $\endgroup$ – Rubio Dec 11 '16 at 12:40
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    $\begingroup$ This is the reason why we always store dates in databases in UTC time. $\endgroup$ – kevin Dec 11 '16 at 15:47
  • $\begingroup$ That's why date representations in most civilized databases use epoch time :) $\endgroup$ – Rubio Dec 11 '16 at 18:24
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    $\begingroup$ @Rubio "The universe is big, it's vast and complicated, and ridiculous. And sometimes, very rarely, impossible things just happen and we call them miracles." $\endgroup$ – Rand al'Thor Dec 11 '16 at 18:29

There is another, I suspect less common, solution.

The mother was on a cruise in the Pacific, and crossed the international date line eastwards between the births, and to make it easy on us, she passes it in a place where she doesn't also change time zone (there are large stretches of the date line where this is the case). If she passes the dateline between the births, and midnight also passes between the births, then the second brother will be nearly a full day older than the first brother.

You could also do the boring variation and say she passes a time zone border westward between the births, but that only gives one brother half an hour on the other.

  • $\begingroup$ I mean "less common" as in "not as likely to actually happen". It is, of course, probably as common to see as an answer to this riddle. $\endgroup$ – Arthur Dec 11 '16 at 16:42
  • $\begingroup$ I don't think this is valid, since the OP specifies that both brothers have the same birthday. (See the comments on the question, and link to a related question where this answer is correct.) $\endgroup$ – Rand al'Thor Dec 11 '16 at 17:12
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    $\begingroup$ @randal'thor They will get the same birthday. That's what happens if midnight also passes between the births, along with the date line. One will be born right before midnight, the other right after midnight, but because we have also gone back a day, those two things happens on the same date. $\endgroup$ – Arthur Dec 11 '16 at 17:21

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