Two islands 3.8 km apart can be 21 hours apart in time
Big Diomede in Russia and Little Diomede in Alaska sit less than 4 km apart in the Bering Strait, close enough to see across on a clear day. The International Date Line runs directly between them, so despite the short distance the two islands can be up to 21 hours apart on the calendar — earning them the nicknames Tomorrow Island and Yesterday Isle.