49 Fun Facts About International Date Line

Through which ocean does the International Date Line run?

The International Date Line runs through the Pacific Ocean from the Arctic to the Southern Ocean, zigzagging around island groups so that each country keeps a single calendar date.

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

The line roughly follows the 180° meridian, on the opposite side of the globe from the prime meridian, though it zigzags to keep island nations on one side.

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

Crossing eastbound, the date goes back one day: a flight leaving Tokyo on Tuesday evening lands in Los Angeles on Tuesday morning, local time.

Is the International Date Line fixed by international law?

No: the line is a cartographic convention with no treaty behind it, which is why island states have shifted it simply by changing their own time zones, as happened in the 1990s and 2011.

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

Travelling west you set the clock Back one hour for each 15° of longitude, losing 24 hours over a full circuit; crossing the date line westbound adds a day to cancel that out.

The line's first deviation from the meridian passes east of Wrangel Island and which Siberian peninsula?

The line jogs east around the Chukchi Peninsula and Wrangel Island, keeping Chukotka and all of Russia on the Asian side of the date line.

Which unofficial US Navy title do sailors earn by crossing the date line?

Crossing the date line admits a sailor to the Domain of the Golden Dragon; the Shellback title is for crossing the equator and Blue Nose for the Arctic Circle.

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

Big Diomede, Russian and a day ahead, is Tomorrow Island, and Little Diomede, in Alaska, is Yesterday Island; only about 2.4 miles of water separates them.

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

Big Diomede is 21 hours ahead of Little Diomede in winter, the islands keeping Russian and Alaskan standard time respectively; Alaskan daylight saving trims the gap to 20 hours.

The date line bends west so which US island chain stays on the American date?

The line swings well west of the meridian to keep The Aleutian Islands, including Attu at their far western end, on the American date side.

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

Howland and Baker, uninhabited US atolls just north of the equator, are the only land on 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?

Kiribati moved the line at the start of 1995 so that its Line Islands, which stretch to about 150°W south of Hawaii, share a date with the capital, Tarawa.

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

The Line Islands keep UTC+14, the latest zone on Earth and 26 hours ahead of the earliest atolls across the line, so their residents greet each new day first.

Which observatory's meridian did the 1884 conference adopt as 0°, placing the date line opposite it?

The International Meridian Conference of October 1884 chose the Greenwich meridian as the world's prime meridian, so the date line came to follow the meridian on the far side of the globe from it.

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

Auckland and Wellington, on New Zealand time, are the first large cities to reach each new date; only small islands on later zones beat them, and Auckland is the country's largest city.

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?

Because the earliest and latest time zones are more than 24 hours apart, 3 calendar dates are in use between 10:00 and 12:00 UTC each day: one ending, one almost everywhere, one just begun.

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

Abulfeda, the Syrian prince and geographer Abu al-Fida, wrote around 1321 that a traveller circling the globe would return a day out of step with those who stayed home.

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

At Cape Verde the crew's count said Wednesday 9 July 1522 while the Portuguese islanders said Thursday; Gasparo Contarini later explained that sailing west had cost them a day.

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

The Philippines, ruled from Mexico City until 1821 and tied to Acapulco by the galleon trade, kept the American date until Governor-General Claveria's reform at the end of 1844.

Which date did Governor-General Claveria drop in 1844 to align his colony's calendar with Asia?

Claveria's decree removed Tuesday, 31 December 1844: Monday 30 December was followed directly by Wednesday 1 January 1845, shifting the colony to the Asian date.

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

Samoa repeated 4 July, US Independence Day, in 1892, living Monday 4 July twice after American traders persuaded King Malietoa Laupepa to adopt the American date.

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

Samoa went straight from Thursday 29 December to Saturday 31 December 2011, deleting Friday, 30 December, so that it moved from the last time zone to among the first.

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?

Tokelau, three atolls some 500 km north of Samoa, skipped the same day because its only shipping and communications links run through Apia.

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

Kwajalein, home to a US Army missile-test base, jumped a day forward to Marshall Islands time by skipping Saturday 21 August 1993; its work week runs Tuesday to Saturday to match 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.

Which country renounced its claims to the Phoenix and Line Islands in a 1979 treaty?

The United States gave up its claims to 14 Phoenix and Line islands, including Canton Island, under the 1979 Treaty of Tarawa with the newly independent state.

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.

In the nautical time-zone letters, which zone is UTC−12, just east of the date line?

Zone Yankee is UTC−12, the zone immediately east of the date line; Mike is UTC+12 on the western side, Zulu is UTC itself and Juliet denotes local time.

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

The Anglo-French Conference on Time-keeping at Sea in 1917 recommended that ships keep zone time in hourly steps, placing the nautical date line on the meridian opposite the prime meridian.

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

Within a nation's 12 nautical mile territorial waters ships are expected to keep that nation's standard time, though at sea the zone time is used mostly for radio and navigation logs.

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

The conference agreed a Universal Day beginning at mean midnight on the prime meridian but declared that it would not propose or agree any time zones, leaving those to individual governments.

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

Antarctica has no single time zone, its stations keeping the time of their home countries or supply bases, so most maps stop the date line at the Southern Ocean rather than drawing it to the pole.

On which day do Seventh-day Adventists in Tonga, in the Western Hemisphere, keep the Sabbath?

Adventists in Tonga keep the Sabbath on Sunday: Tonga lies in the Western Hemisphere but keeps the Asian date, so its Sunday is the same solar day as Saturday across the line.

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

In Three Sundays in a Week, Captains Pratt and Smitherton have circled the globe in opposite directions, so one is a day behind London and the other a day ahead, yielding three Sabbaths.

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

Fogg reaches London at 8:50 pm, believing he is 5 minutes past his 8:45 deadline, until Passepartout learns it is a day earlier than they thought; sailing east, Fogg had seen eighty sunrises to London's seventy-nine.

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

The Island of the Day Before (1994) maroons Roberto della Griva on the abandoned ship Daphne off an island across the date line, which he cannot reach because he cannot swim.

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.

Big Diomede, on the Russian side of the date line, is also known by which name?

Big Diomede is Ratmanov Island to Russians, after naval officer Makar Ratmanov; Little Diomede, across the line in Alaska, carries the Russian name Krusenstern Island.

The date line passes between Attu Island and which Russian island group to its west?

The Commander Islands, Bering and Medny, are the nearest Russian land west of Attu; the line passes between the two groups before bending back east to rejoin the meridian.

Which three US insular areas lie west of the date line, on the Asian date?

Guam, Northern Marianas and Wake Island lie west of the line and keep the Asian date, hence Guam's motto 'Where America's Day Begins'.

What term describes the meridian directly opposite the prime meridian, which the date line roughly follows?

The meridian opposite the prime meridian is the antimeridian; together they form a great circle, and the date line departs from this antimeridian only to keep island groups on one date.

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

Around the June solstice the Kamchatka (UTC+12) zone wins: its far-northern reaches above the Arctic Circle have the midnight sun, so they are in daylight the instant their date changes, hours before sunrise in any later zone.

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

Amundsen-Scott and McMurdo, both US stations keeping New Zealand time (UTC+13 in the austral summer), are under the midnight sun in December, so they see the new day's light as soon as it begins.

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

Carteret logged Pitcairn about 188 nautical miles west of its true position in 1767, so later ships could not find it, which made it a safe refuge for the Bounty mutineers in 1790.

Which inhabited Line Islands atoll was marketed as the first to greet the year 2000?

Kiritimati, also known as Christmas Island and the largest coral atoll by land area, lies in the latest time zone and was promoted as the first inhabited place to enter the year 2000.

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

Jumu'ah is held on the Local Friday everywhere, since Islamic law keys the weekly prayer to the local day; only the lunar months, set by crescent sightings, are unaffected by the line.