50 Fun Facts About International Date Line

Through which ocean does the International Date Line run?

It roughly follows the 180° meridian, halfway round the world from Greenwich, bending around islands and territories.

Which line of longitude does the International Date Line roughly follow?

It sits opposite the IERS Reference Meridian, the successor to the Greenwich prime meridian.

What happens to the calendar date when you cross the date line travelling eastbound?

Westbound travellers do the reverse and jump forward a day.

Is the International Date Line fixed by international law?

That is why countries through whose waters it passes have been able to move it for their own convenience.

Travelling westward around the world, how must you set your clock for every 15° of longitude crossed?

Then, at the date line, the clock jumps forward 24 hours to make up for it.

The date line's first deviation from 180° passes east of Wrangel Island and which peninsula, Siberia's easternmost tip?

That keeps all of Russia on the western, Asian-date side of the line.

In the Bering Strait the date line runs between which pair of rocky islets, one Russian and one American?

They sit about 3.8 km apart yet are up to 21 hours apart on the clock.

Because of the date line, Big Diomede and Little Diomede are nicknamed what?

Big Diomede belongs to Russia and Little Diomede to Alaska; the gap between them is about 2.4 miles.

How far ahead of Little Diomede is Big Diomede on the clock in winter?

It drops to 20 hours in summer because of daylight saving on the American side.

The date line bends west of 180° so that which US island chain stays on the American date side?

It squeezes between Attu, the westernmost Aleutian, and Russia's Commander Islands.

Which two uninhabited US atolls near the equator have the earliest time on Earth, UTC−12?

When it is Tuesday morning in Britain, it is still Monday evening there.

Around which country does the date line swing far to the east, almost reaching 150°W?

Its Line Islands, south of Hawaii, run on UTC+14, the latest time on Earth.

What is the latest time zone on Earth, used by the Line Islands south of Hawaii?

Its inhabitants ring in each new day and each New Year before anyone else.

Which two territories does the date line pass between in the South Seas, leaving them a day apart?

Christians in one celebrate Christmas a full day before their neighbours in the other, a few dozen miles away.

Which are the first major cities to experience a new day, according to the clock?

New Zealand runs on UTC+12, or UTC+13 in summer, second only to the tiny UTC+14 islands.

Which atoll was renamed after 1994 because it would be among the first land to reach 1 January 2000?

At the equinoxes it is also the first place to see the daylight of a new day.

For two hours every day, how many different calendar dates exist simultaneously on Earth?

Between 10:00 and 12:00 UTC it can be Monday on Baker Island, Tuesday almost everywhere and Wednesday in Kiritimati.

Which 14th-century Arab geographer predicted that circumnavigators would find themselves a day out?

His prediction was confirmed in 1522 when Magellan's surviving crew reached Cape Verde.

Where did the Magellan-Elcano survivors discover in 1522 that their ship's log was a day behind?

They thought it was Wednesday 9 July; the locals said Thursday. Cardinal Gasparo Contarini first explained why.

Which Asian country, governed from Mexico, sat on the American side of the date line until 1844?

Its main link was the galleon route to Acapulco, so it was a day behind its Asian neighbours for 323 years.

To catch up with Asia, which date did Governor-General Claveria drop from the Philippine calendar?

Monday 30 December was followed straight by Wednesday 1 January 1845, and Guam and the Marianas changed too.

What else changed when Alaska moved to the east side of the date line on its 1867 purchase?

Saturday 7 October (Julian) became Friday 18 October (Gregorian), now celebrated as Alaska Day.

When Samoa switched to the American date in 1892, which day did it live through twice?

American traders talked King Malietoa Laupepa into the change.

In 2011 Samoa jumped back to the west side of the date line by deleting which day from its calendar?

Being 21 hours behind Australia and New Zealand, its main trading partners, left only four shared working days a week.

Why did Samoa move across the date line in 2011?

Tokelau, whose links run through Samoa, crossed with it, one hour later because it had no summer time.

Which New Zealand territory north of Samoa crossed the date line along with Samoa in 2011?

Its transport and communications links to the world all pass through Samoa.

Which US-run Marshall Islands atoll deleted Saturday 21 August 1993 to leave Hawaiian time?

Its work week was shifted to Tuesday–Saturday to line up with a Monday–Friday week in Hawaii.

Why was the date line moved around the eastern islands of the Gilberts' successor state in 1994?

Friday 30 December 1994 was followed by Sunday 1 January 1995; the Millennium boost was a happy side effect.

From which country did the newly independent Gilbert Islands acquire the Phoenix and Line Islands in 1979?

The colony had been centred on the Gilbert Islands, just west of the line.

Which two territories crossed east of the date line in 1899 as British protectorates?

Both stayed on the eastern side and, as of 2025, were still a day behind Samoa and Tonga.

In what year did Tahiti abandon the eastern-hemisphere date brought by 1797 missionaries for the western one?

The order came from the French commissioner Bruat and the regent Paraita after the Franco-Tahitian War.

Which date did the Pitcairn mutineers first keep, as islanders 'Thursday October' and 'Friday October' suggest?

Captain Carteret had mislocated the island by 188 nautical miles in 1767, which helped the mutineers stay hidden.

The nautical date line used by ships at sea stems from which 1917 agreement?

It follows 180° exactly except where territorial waters interrupt it, giving a dashed pole-to-pole line.

Ships are meant to adopt a country's standard time when within how many nautical miles of its land?

In practice ships use those zones only for radio; internal meal and watch times follow a zone of their own choosing.

The 1884 International Meridian Conference agreed the Universal Day but explicitly declined to do what?

That is why no treaty has ever fixed the date line cartographers draw.

On most maps, into which continent is the date line conventionally not drawn?

Antarctica has multiple time zones, and both CIA and British Nautical Almanac maps stop the line short of it.

In Tonga, west of the date line but east of 180°, on which day do Seventh-day Adventists keep the Sabbath?

The church treats Tonga's Sunday as the same physical day as Saturday east of the line.

In which 1841 Poe story do two captains who circled the globe in opposite directions disagree on the day?

One captain reckons it is Saturday, the other Monday, while at home it is Sunday.

In Around the World in Eighty Days, Fogg thinks he lost his bet by how many minutes before realising he gained a day?

Verne explains that Fogg, going east, saw the sun cross the meridian eighty times while London saw it seventy-nine.

Which Umberto Eco novel strands its hero on a becalmed ship within sight of land across the date line?

Unable to swim, he speculates ever more wildly about the line's physical and metaphysical meaning.

Bret Harte's 1867 poem 'The Lost Galleon' concerns a Spanish ship sailing between Acapulco and which port?

The poem is historically off: in 1641 the de facto date line ran west of the Philippines.

Why did Vitus Bering name the two Bering Strait islets he sighted on 16 August 1728 as he did?

The Russian Orthodox Church commemorates the Greek saint on that day.

The date line passes between Attu, the westernmost Aleutian, and which Russian island group?

After that jog it bends back to 180° so all of Russia lies west of the line.

Which three US insular areas lie west of the date line, unlike the rest of the United States?

They keep an Asian date while Howland and Baker to the east use the earliest zone on Earth.

At the equinoxes, which uninhabited spot in Kiribati is the first place on Earth to see a new day's light?

It is the easternmost land west of the date line; near the December solstice, Antarctic bases with midnight sun win instead.

Around the June solstice, the first places to see a new day's daylight lie in which zone?

Far northern spots there experience the midnight sun, so they see the new day's light before anywhere else.

Which Antarctic stations on New Zealand time see the first daylight of a new day near the December solstice?

Scott Base and Zucchelli Station share the honour thanks to the polar midnight sun.

Captain Carteret's 1767 discovery of Pitcairn misplaced the island by about how far to the west?

The error meant Fletcher Christian searched in the wrong spot, which helped persuade the Bounty mutineers to settle there.

Which inhabited Kiribati island in the Line Islands was marketed as the first to greet the year 2000?

Also known as Christmas Island, it benefited from the 1994 shift that put the whole country west of the line.

On which day do Muslim communities near the date line hold the Jumu'ah prayer?

The Islamic lunar months are unaffected by the line, since they depend only on sighting the new crescent moon.