Islands only three miles apart are separated by 21-hour time difference

A TikTok user has gone viral after explaining how two islands have a 21-hour time difference despite being just three miles apart.

The Diomede Islands are separated by the International Date Line which passes through the Pacific Ocean and marks the boundary between one calendar day and the next.

It means the island of Big Diomede is almost a day ahead of its neighbour Little Diomede despite sitting side by side in the Bering Strait between mainland Alaska and Siberia.

Big Diomede is located on the Russian side while Little Diomede is on the US side.

The ice bridge that forms between the two islands in winter makes it possible, although illegal, to walk the short distance between them and literally travel through time.

Big Diomede, owned by Russia, is uninhabited while Little Diomede, owned by US, has a population of 110 people (Gamma-Rapho via Getty Images)

It also means it is theoretically possible to walk from Russia to the US and the journey can also be made by sailboat, kayak or swimming.

The astonishing fact was highlighted in a TikTok video demonstrating some of the unusual places on Earth.

In the clip, a voiceover says: "There are some weird places in the world. These are the Diomede Islands.

"They sit on a Date Line. They have a 20-hour time difference even though they are only 2.5 miles apart."

(Gamma-Rapho via Getty Images)

One person joked: "Imagine working on both islands. You could do two eight hour shifts in the same day."

A second person said: "You could be on one island on New Year's and go back a year."

While another replied "Double NYE, imagine the hangover."

The islands are named after the Greek Saint Diomede. They were discovered by Danish-Russian navigator Vitus Bering on August 16, 1728.

It marks the day on which the Russian Orthodox Church celebrates the memory of Saint Diomede.

Native people still live on Little Diomede which has a population of around 110 people.

In Big Diomede, the Soviet government relocated its indigenous population to mainland Russia and the island is only inhabited by military units.

Those living on the Russian side were forcibly resettled in Siberia after the start of the Cold War more than 70 years ago and the border was closed.