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49 free International Date Line trivia questions with answers — geography quiz, new questions added Aug 2026.
This International Date Line trivia quiz covers the imaginary boundary between one calendar day and the next, and the surprisingly long list of countries that have hopped across it. The easy questions ask which ocean it runs through, which line of longitude it roughly follows, what happens to the date when you cross it, and which country's islands see the New Year first. Then it works through the zigzags: the Diomedes, the Aleutians, the giant bulge around Kiribati and the gap between Samoa and American Samoa. The hard end is for people who enjoy calendar arithmetic: the Arab geographer who predicted the lost day, Magellan's crew discovering it at Cape Verde, the Philippines skipping 31 December 1844, Alaska's date jumping back at the 1867 handover, Samoa repeating the Fourth of July in 1892 and deleting a Friday in 2011, Kwajalein's Tuesday-to-Saturday work week, the two-hour window with three dates on Earth, and the fiction from Poe to Umberto Eco built on the paradox. Every answer was checked against the encyclopaedia entries on the International Date Line and the Diomede Islands before publishing, and the supporting sentence is stored with each question. Our time zones, Pacific islands and world geography quizzes are natural next stops.
30 of 49 questions with answers and explanations. Play the quiz
Q 01Through which ocean does the International Date Line run?
Pacific
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.
Q 02Which line of longitude does the International Date Line roughly follow?
180°
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.
Q 03What happens to the calendar date when you cross the date line travelling eastbound?
It goes back one day
Crossing eastbound, the date goes back one day: a flight leaving Tokyo on Tuesday evening lands in Los Angeles on Tuesday morning, local time.
Q 04Is the International Date Line fixed by international law?
No, it is a cartographic convention
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.
Q 05Travelling westward around the world, how must you set your clock for every 15° of longitude crossed?
Back one hour
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.
Q 06The line's first deviation from the meridian passes east of Wrangel Island and which Siberian peninsula?
Chukchi
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.
Q 07Which unofficial US Navy title do sailors earn by crossing the date line?
Golden Dragon
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.
Q 08Because of the date line, Big Diomede and Little Diomede are nicknamed what?
Tomorrow Island and Yesterday Island
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.
Q 09How far ahead of Little Diomede is Big Diomede on the clock in winter?
21 hours
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.
Q 10The date line bends west so which US island chain stays on the American date?
The Aleutian Islands
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.
Q 11Which two uninhabited US atolls near the equator have the earliest time on Earth, UTC−12?
Howland and Baker
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.
Q 12Around which country does the date line swing far to the east, almost reaching 150°W?
Kiribati
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.
Q 13What is the latest time zone on Earth, used by the Line Islands south of Hawaii?
UTC+14
Q 21Which date did Governor-General Claveria drop in 1844 to align his colony's calendar with Asia?
Tuesday, 31 December
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.
Q 22When Samoa switched to the American date in 1892, which day did it live through twice?
4 July, US Independence Day
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.
Q 23In 2011 Samoa jumped back to the west side of the date line by deleting which day from its calendar?
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.
Q 14Which observatory's meridian did the 1884 conference adopt as 0°, placing the date line opposite it?
Greenwich
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.
Q 15Which are the first major cities to experience a new day, according to the clock?
Auckland and Wellington
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.
Q 16Which atoll was renamed after 1994 because it would be among the first land to reach 1 January 2000?
Caroline Island, now Millennium Island
At the equinoxes it is also the first place to see the daylight of a new day.
Q 17For two hours every day, how many different calendar dates exist simultaneously on Earth?
3
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.
Q 18Which 14th-century Arab geographer predicted that circumnavigators would find themselves a day out?
Abulfeda
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.
Q 19Where did the Magellan-Elcano survivors discover in 1522 that their ship's log was a day behind?
Cape Verde
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.
Q 20Which Asian country, governed from Mexico, sat on the American side of the date line until 1844?
Philippines
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.
Friday, 30 December
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.
Q 24Why did Samoa move across the date line in 2011?
Australia and New Zealand were now its main trading partners
Tokelau, whose links run through Samoa, crossed with it, one hour later because it had no summer time.
Q 25Which New Zealand territory north of Samoa crossed the date line along with Samoa in 2011?
Tokelau
Tokelau, three atolls some 500 km north of Samoa, skipped the same day because its only shipping and communications links run through Apia.
Q 26Which US-run Marshall Islands atoll deleted Saturday 21 August 1993 to leave Hawaiian time?
Kwajalein
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.
Q 27Why was the date line moved around the eastern islands of the Gilberts' successor state in 1994?
The country straddled it, leaving four shared weekdays
Friday 30 December 1994 was followed by Sunday 1 January 1995; the Millennium boost was a happy side effect.
Q 28Which country renounced its claims to the Phoenix and Line Islands in a 1979 treaty?
The United States
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.
Q 29Which two territories crossed east of the date line in 1899 as British protectorates?
The Cook Islands and Niue
Both stayed on the eastern side and, as of 2025, were still a day behind Samoa and Tonga.
Q 30In what year did Tahiti abandon the eastern-hemisphere date brought by 1797 missionaries for the western one?
1846
The order came from the French commissioner Bruat and the regent Paraita after the Franco-Tahitian War.