A child is born on August 19th 2016 00:12 (local time) on timezone GMT + 1.
Another child is born on August 18th 2016 23:48 (local time) on timezone GMT.
Which one is the oldest?
Note: Not sure I tagged this properly. I could use some help.
GMT child is older, as they'll celebrate/commiserate their birthday the day before GMT+1 child, despite being born 36 minutes later.
There will be a point where GMT child is 21 years old whilst GMT+1 child is 20, for example (which would be incredibly annoying if they were attempting to go to a bar in the USA (GMT-4 to GMT-10, I believe). That's largely moot, though - since they were likely born in the UK and France, GMT+1 child can start drinking 1 year and 364 days before GMT child)
as the birth time of the first child in GMT is August 18th 2016 23:12, he is 36 minutes older than the second child. At least technically he was born 36 minutes earlier than the other child, though the former will always celebrate his birthday one day later than the latter.
@elias answer is correct but
It depends who was born first. If the child born in the GMT + 1 timezone was born first then he'd be the oldest regardless of the the time in GMT.
Think of it this way. If you were born at 11PM on the 11th in America, lived there for 20 years then moved to England, you are not going to change your birthday to the 12th are you?