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This is updated version for Another Twin Puzzle: Three Days Difference

Today is my first day joining my college's Puzzle Club. It is so much fun gathering in a group with similar interests! I meet a lot of new friends and of course asked their contact number to discuss and solve puzzles. We are asked to create a simple-yet-amusing puzzle for sharing on the next week's meeting.

I usually like to create a puzzle based on a real-life situation. The idea comes from everywhere, literally, everywhere. I just came up with a puzzle based on every club member's age and birthday, so I try to collect data by asking them all by SMS. And this.. is the cause why I'm being puzzled now.

One More Twin Puzzle: Four Days Difference?!

I asked all of them this question: "When is your birthday?"

Chuck replied fast: "Lol, it's just 4 days ago fyi!" and 20 minutes later another member, Delilah, said: "My birthday is actually 8 days ago." Not only that, she also wrote another message: "But believe me, I and Chuck have sister-and-brother relationship... and also.... we are twin, ;) ."

So here is the puzzle for you: Please explain what happened! Is it possible that Chuck and Delilah are really twin?

(NB. by "twin", we assume that they are born by the same mother and only separated by a couple of minutes.)

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  • $\begingroup$ was the pregnancy incredibily protracted? $\endgroup$
    – JMP
    Commented Dec 29, 2017 at 10:21
  • $\begingroup$ The answers are assuming you asked this in a leap year, and you don't counter that. So just to make sure: are we to ignore the fact that you said this happened today? (The same applies to your other question.) $\endgroup$
    – hvd
    Commented Dec 29, 2017 at 10:30
  • $\begingroup$ @hvd yeah, you may ignore the fact that I really said today is "today". i.e. you can assume it happened on a leap year. $\endgroup$
    – athin
    Commented Dec 29, 2017 at 10:59

3 Answers 3

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This was easy -

What probably happened was

their mother was in a boat which was going east. She gave birth to Delilah on 27 February at some time around 11:59 p.m. Then, the boat crossed the International Date Line which made the date 28 February. And because of the 11:59 p.m., it soon became 1 March. Then, Chuck was born.

What you did was

you first asked Chuck some time on 5 March after 11:40 p.m. when it was a leap year. He answered that his birthday was 4 days ago. 20 minutes later, when Delilah answered, it had become 6 March. So, it was actually 8 days after her birthday.

Here's a calendar to make this easier -

27 February (Delilah's birthday),
28 February (After crossing the IDL)
29 February (Extra day due to you asking on a leap year)
1 March (Chuck's Birthday)
2 March
3 March
4 March
5 March (Day you asked Chuck)
6 March (Day you asked Delilah)

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    $\begingroup$ Nice! Actually this is the "fittest" scenario given that "today" is a usual day (except when they were born). Combining with @boboquack 's answer, 5 days apart is possible. Welp, I underestimated all of these scenarios XD $\endgroup$
    – athin
    Commented Dec 29, 2017 at 11:05
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So…

Similarly to the previous problem, Chuck and Deliah were born on Feb 28/Mar 1 on a non-leap year

But:

It could be a leap year, and furthermore Chuck could be in a time zone where it is just before midnight on 5 March while Deliah messages later just after midnight in a time zone where it is now 7 March (i.e. the two time zones are 24 hours apart, like Niue at UTC-11 and Samoa at UTC+13)

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    $\begingroup$ That's a beautiful answer! Given that they are currently on a same college, it is assumed that they are currently live on the same timezone, :) ... or do I need to make another puzzle to make it 5 days apart Orz ... puzzler in this Puzzling community are brilliant people for sure. $\endgroup$
    – athin
    Commented Dec 29, 2017 at 2:59
  • $\begingroup$ @athin Ah, but are they at home? $\endgroup$
    – boboquack
    Commented Dec 29, 2017 at 7:45
  • $\begingroup$ well, i guess i need to really constraint the problems. and yes, asumming they are currently at home. $\endgroup$
    – athin
    Commented Dec 29, 2017 at 11:01
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Perhaps Chuck and his twin brother were born a year and four days after his sister Delilah and her twin sister...

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  • $\begingroup$ That can be possible, but how if they have no other siblings (beside those two?). $\endgroup$
    – athin
    Commented Dec 29, 2017 at 6:20
  • $\begingroup$ Sadly, they have both died. Freak incident at a twin convention. :C $\endgroup$
    – HoratioCain
    Commented Dec 29, 2017 at 8:39

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