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        riddles >> hard >> Hard: Birthday twins
        
(Message started by: Your name here on Jul 26^th, 2002, 12:51pm)

Title: Hard: Birthday twins
Post by Your name here on Jul 26^th, 2002, 12:51pm

If one twin was born at 11:59:59 PM Feb 28 and the other at 12:01:01 AM March 1, their birthdays will be 2 days apart on leap years.

Title: Re: Hard: Birthday twins
Post by Mark Davis on Jul 26^th, 2002, 8:35pm

Uh, but the older one celebrates 2 days AFTER the younger one. How do they get the order switched?

Title: Re: Hard: Birthday twins
Post by tim on Jul 27^th, 2002, 1:45am

My first guess would be timezones.

If Sheila was born first on the western side of the date line, she may have a birthdate of March 1. He-man could be born a tiny bit later (but after the ship crosses the dateline eastward) and have a birthdate on February 28.

Every leap year, He-man celebrates on Feb 28, and two days later Sheila celebrates on Mar 1.

It can get worse: Fiji has daylight savings time, and it can (for example) be just after midnight in the morning of December 10 while it is still just before midnight on December 8 in some places on the eastern side of the date line. This could cause all sorts of fun.

But you don't even need the date-line. Crossing any time-zone boundary just between their births at the right moment could cause Sheila to have a birthday the day after He-man despite being older.

It gets better still. Both Sheila and He-Man coudl have been born right in the same day without any special timing of their birth matching timezone crossings:

Many countries have had differing calendars in the past, offset by varying numbers of days from each other. The most famous would have been the geographically ragged switch from the Julian to Gregorian calendars. If Sheila celebrated her birthday in a different country from He-Man, that could easily account for a couple of days difference. It could even be a couple of weeks!