Russia

Diomede Islands

Two islands just 4 km apart separated by an International Border and Date Line. 

https://www.atlasobscura.com/places/diomede-islands

Despite being separated by just 3.8 kilometers, the Diomede Islands find themselves not only in different countries, but also twenty hours apart, due to the International Date Line passing between them.

Diomede Islands

• The Russian island of Big Diomede (part of Chukotka Autonomous Okrug), also known as Imaqliq, Inaliq,  Nunarbuk or Ratmanov Island
• The U.S. island of Little Diomede (part of Alaska) or Ignaluk, also known as Krusenstern Island^[a]

The Diomede Islands are located in the middle of the Bering Strait between mainland Alaska and Siberia, which borders the Chukchi Sea to the north and the Bering Sea to the south. 9.3 km (5.8 mi) to the southeast is Fairway Rock, which is generally not considered part of the Diomede Islands. Because they are separated by the International Date Line, Big Diomede is almost a day ahead of Little Diomede, but not completely; due to locally defined time zones, Big Diomede is only 21 hours ahead of Little Diomede (20 in summer).^[2] Because of this, the islands are sometimes called Tomorrow Island (Big Diomede) and Yesterday Island (Little Diomede).

Diomede Islands

Additional information
Demographics
Administration
Geography
Russian: острова Диомида Inupiaq: Ignaluk
Diomede Islands: Little Diomede (left) and Big Diomede (right). Picture taken looking southwards
Satellite photo of the Bering Strait, with the Diomede Islands at center
Location	Bering Strait
Coordinates	65°47′N 169°01′WCoordinates: 65°47′N 169°01′W
Total islands	2
Russia / United States
Population	0 (Big Diomede) 135[1] (Little Diomede) (2011)
Time zones	Alaska Time – UTC -9/-8 Kamchatka Time – UTC+12