Big Diomede and Little Diomede are two islands in the Bering Strait between Alaska and Siberia. Big Diomede belongs to Russia and Little Diomede belongs to the US. The International Date Line runs in between the islands and acts as an international border. Even though the distance between them is only four kilometres, they are 21 hours apart due to local time zones. For this reason, they were nicknamed Tomorrow Island (Big) and Yesterday Isle (Little). In the winter, the rocky flat-topped islands are sometimes connected by an ice bridge.