The Diomede Islands (/ˌdaɪ.əˈmiːdiː/; Russian: острова́ Диоми́да, romanized: ostrova Diomida), also known in Russia as Gvozdev Islands (Russian: острова́ Гво́здева, romanized: ostrova Gvozdeva), consist of two rocky, mesa-like islands. One is the Russian island of Big Diomede (part of Chukotka). The other is the U.S. island of Little Diomede (part of Alaska). The Diomede Islands are located in the middle of the Bering Strait between mainland Alaska and Siberia. At their closest points, the two islands are approximately 2.4 miles away from each other.
Because they are separated by the International Date Line, Big Diomede is almost a day ahead of Little Diomede; due to locally defined time zones, Big Diomede is 21 hours ahead of Little Diomede (20 in summer). Because of this, the islands are sometimes called Tomorrow Island (Big Diomede) and Yesterday Island (Little Diomede).