50 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 50 questions with answers and explanations. Play the quiz
Q 01Through which ocean does the International Date Line run?
Pacific
It roughly follows the 180° meridian, halfway round the world from Greenwich, bending around islands and territories.
Q 02Which line of longitude does the International Date Line roughly follow?
180°
It sits opposite the IERS Reference Meridian, the successor to the Greenwich prime meridian.
Q 03What happens to the calendar date when you cross the date line travelling eastbound?
It goes back one day
Westbound travellers do the reverse and jump forward a day.
Q 04Is the International Date Line fixed by international law?
No, it is a cartographic convention
That is why countries through whose waters it passes have been able to move it for their own convenience.
Q 05Travelling westward around the world, how must you set your clock for every 15° of longitude crossed?
Back one hour
Then, at the date line, the clock jumps forward 24 hours to make up for it.
Q 06The date line's first deviation from 180° passes east of Wrangel Island and which peninsula, Siberia's easternmost tip?
Chukchi
That keeps all of Russia on the western, Asian-date side of the line.
Q 07In the Bering Strait the date line runs between which pair of rocky islets, one Russian and one American?
The Diomedes
They sit about 3.8 km apart yet are up to 21 hours apart on the clock.
Q 08Because of the date line, Big Diomede and Little Diomede are nicknamed what?
Tomorrow Island and Yesterday Island
Big Diomede belongs to Russia and Little Diomede to Alaska; the gap between them is about 2.4 miles.
Q 09How far ahead of Little Diomede is Big Diomede on the clock in winter?
21 hours
It drops to 20 hours in summer because of daylight saving on the American side.
Q 10The date line bends west of 180° so that which US island chain stays on the American date side?
The Aleutian Islands
It squeezes between Attu, the westernmost Aleutian, and Russia's Commander Islands.
Q 11Which two uninhabited US atolls near the equator have the earliest time on Earth, UTC−12?
Howland and Baker
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
Its Line Islands, south of Hawaii, run on UTC+14, the latest time on Earth.
Q 13What is the latest time zone on Earth, used by the Line Islands south of Hawaii?
UTC+14
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?
Q 21To catch up with Asia, which date did Governor-General Claveria drop from the Philippine calendar?
Tuesday, 31 December
Monday 30 December was followed straight by Wednesday 1 January 1845, and Guam and the Marianas changed too.
Q 22What else changed when Alaska moved to the east side of the date line on its 1867 purchase?
It went from the Julian to the Gregorian calendar
Saturday 7 October (Julian) became Friday 18 October (Gregorian), now celebrated as Alaska Day.
Q 23When Samoa switched to the American date in 1892, which day did it live through twice?
Samoa and American Samoa
Christians in one celebrate Christmas a full day before their neighbours in the other, a few dozen miles away.
Q 15Which are the first major cities to experience a new day, according to the clock?
Auckland and Wellington
New Zealand runs on UTC+12, or UTC+13 in summer, second only to the tiny UTC+14 islands.
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
Between 10:00 and 12:00 UTC it can be Monday on Baker Island, Tuesday almost everywhere and Wednesday in Kiritimati.
Q 18Which 14th-century Arab geographer predicted that circumnavigators would find themselves a day out?
Abulfeda
His prediction was confirmed in 1522 when Magellan's surviving crew reached Cape Verde.
Q 19Where did the Magellan-Elcano survivors discover in 1522 that their ship's log was a day behind?
Cape Verde
They thought it was Wednesday 9 July; the locals said Thursday. Cardinal Gasparo Contarini first explained why.
Q 20Which Asian country, governed from Mexico, sat on the American side of the date line until 1844?
Philippines
Its main link was the galleon route to Acapulco, so it was a day behind its Asian neighbours for 323 years.
4 July, US Independence Day
American traders talked King Malietoa Laupepa into the change.
Q 24In 2011 Samoa jumped back to the west side of the date line by deleting which day from its calendar?
Friday, 30 December
Being 21 hours behind Australia and New Zealand, its main trading partners, left only four shared working days a week.
Q 25Why 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 26Which New Zealand territory north of Samoa crossed the date line along with Samoa in 2011?
Tokelau
Its transport and communications links to the world all pass through Samoa.
Q 27Which US-run Marshall Islands atoll deleted Saturday 21 August 1993 to leave Hawaiian time?
Kwajalein
Its work week was shifted to Tuesday–Saturday to line up with a Monday–Friday week in Hawaii.
Q 28Why 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 29From which country did the newly independent Gilbert Islands acquire the Phoenix and Line Islands in 1979?
The United States
The colony had been centred on the Gilbert Islands, just west of the line.
Q 30Which 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.