[layman51]

You reminded me of some riddle I had once read that was about trying to figure out how someone could be born one year later but still be older than someone born in previous year. The answer to the riddle also relies on timezones. For sure, birthdates involve time zones.

The riddle explanation was something like: A baby is born in New York City at 12:15 AM on January 1. Thirty minutes later, another baby is born in Los Angeles, where the local time is 9:45 PM on December 31. Although the New York baby is actually older by 30 minutes, the calendar dates make it appear as though the Los Angeles baby was born first.

[WorldMaker]

The other biggest fun trick of timezone math to a riddle like that would be the International Date line where a baby born on one side of it can be born on the "day before" by calendar reckoning despite being born 30 minutes after the other side of the line.

[rmunn]

Fraternal (not identical) twins, born aboard a ship traveling west to east across the Pacific. One of them officially born January 1st, 2016. The younger-by-30-minutes twin officially born December 31st, 2015. They'll have the hardest time persuading people that they're really twins once they're grown up.

[hdjrudni]

Isn't that precisely the same?

Doesn't even have to be the International Date line, any two timezones work.