Question

A passenger on a cruise liner celebrates his birthday one evening with a party. It is June 18th. The ship is in zone −12 and at zone time 23h 36m, June 18th, it crosses the date line. Show that the passenger may legitimately have another birthday party for the same birthday.

Answer 1

As the ship is crossing the date line from -12 to +12, that is in the direction from East to West, so 24 hours are added. That means the new date will be June 19th, 23:36; so no additional birthday party.