The Diomede Islands are two islands in the Arctic Ocean, between Alaska and Siberia. Despite the distance being 4 kilometres, there is a time difference of 21 hours between them. Why?
I’m asking because it’s quite difficult for me to grasp the concept of time differences when the physical distances are so short. I know of the International Date Line, but I’m not sure what it entails. If any nerds would care to enlighten me, I’d appreciate it!
(This question also applies to the Kiribati Island and Howland Island; the time difference is ~26 hours, yet the physical distance is only ~2160 km?)
We have our time zone “origin” at the prime meridian (Greenwich, UK). As you move one time zone to the east, local time is (generally) an hour later. As you go west, it’s an hour earlier. As each time zone spans each direction of the globe, going an ~hour earlier/later along the way, they’re eventually going to meet. One direction lost 12 hours, the other gained 12 hours. That’s the international date line, where they are 12-(-12)=24 hours apart.
They could have put them in the same time zone (it is a human construct, after all) but since they are associated with two countries, it makes sense to keep each island with its respective country. Since it’s right around the opposite side of the prime meridian, it means you’re roughly a day apart.