97 Fun Facts About Time Zones

Which imaginary line is the zero point for the world's time zones?

The prime meridian. Delegates meeting in Washington in 1884 fixed it at Greenwich, partly because the United States had already built its railway time zones on that line.

Before standard time, clocks in which English city ran about ten minutes behind London's?

Bristol. It lies about 2.5 degrees west of London, and the Sun takes four minutes to cross each degree; the clock on the city's Exchange still carries a second minute hand for the difference.

From 1852, which technology carried Greenwich time across Britain?

The telegraph. A master clock at Greenwich sent signals down the wires, and by the mid-1850s almost every public clock in Britain showed London time; the law caught up only in 1880.

Which colony adopted a nationwide standard time in 1868, 11½ hours ahead of GMT?

New Zealand. Its clocks kept that odd half hour until a wartime emergency put them forward all year round, a change made permanent in 1946 that left the country a round 12 hours ahead.

Which country set its clocks back 30 minutes in 2015 to shed a legacy of Japanese rule, then reversed it in 2018?

North Korea. It created Pyongyang Time for the 70th anniversary of liberation from Japan, then moved back after a summit with the South so that both Koreas would share one clock again.

November 18, 1883, when US railroads reset their clocks, is remembered as what?

The Day of Two Noons. Railroad station clocks were reset as standard-time noon reached each zone, so a clock that had already passed midday by local sun time came round to noon again.

Which US state began observing daylight saving time statewide only in 2006?

Indiana. For decades most of its counties stayed on standard time all year while those near Chicago and Evansville changed their clocks, so the gap between neighbours depended on the season.

Which federal department sets time zone boundaries in the United States?

Transportation. A 1918 law gave the job to the Interstate Commerce Commission, then the only federal transport regulator, and Congress moved it across when the department was created in 1966.

Which Canadian railway engineer proposed a worldwide system of 24 time zones in the 1870s?

Sandford Fleming. Railways had made town-by-town sun time unworkable, and he pressed his scheme until Washington hosted the 1884 conference at which nations agreed to take Greenwich as their common reference.

Which Atlantic Canadian island keeps its own time zone, half an hour ahead of the mainland beside it?

Newfoundland. Its clocks follow the Sun at St. John's, the capital on its eastern tip, almost exactly three and a half hours behind Greenwich; as a separate dominion it kept that time when zones came in.

Which Himalayan country keeps one of the world's rare quarter-hour offsets, UTC+05:45?

Nepal. Its time is reckoned from the meridian of Gaurishankar, a mountain east of Kathmandu, which is why its clocks sit an odd quarter of an hour off its neighbours'.

Which country briefly cut its 11 time zones to nine?

Russia. Dmitry Medvedev trimmed the map and kept summer time all year, saying clock changes even upset cows; after complaints about dark winter mornings, both reforms were undone in 2014.

Which country spans five geographic time zones yet keeps a single official clock?

China. Beijing time is the only official clock, so in the far west the Sun can be highest at three in the afternoon, and many people in Xinjiang keep an unofficial time two hours behind.

Which land border has the greatest time-zone jump on Earth, 3.5 hours?

Afghanistan–China. The record jump, from UTC+04:30 to UTC+08:00, comes at one of the world's emptiest frontiers: a short mountain border whose crossing, the Wakhjir Pass, has no road.

Which large country keeps a single half-hour offset, UTC+05:30, across its whole width?

India. The single clock is a legacy of British rule, and the country is so wide that the Sun rises nearly two hours earlier in its far east than in its far west.

Tea gardens in which Indian state run an hour ahead of IST on "Bagan time"?

Assam. Its tea estates keep "bagan time" as an informal zone of their own because the Sun is up so early in the country's north-east.

Which letter stands for UTC in the lettered time zone system, giving UTC its radio nickname?

Z, hence "Zulu time". Zulu is the radio alphabet's word for Z, and weather services around the world log their observations in Z time so that readings from different places line up.

Why is Coordinated Universal Time abbreviated UTC rather than CUT?

A compromise to match all languages. English word order gives CUT and French gives TUC, so the standard's designers picked one neutral abbreviation that favours neither language.

What is occasionally added to UTC?

A leap second. First inserted in 1972, the extra seconds cause such trouble for computer networks that the world's metrologists voted in 2022 to stop adding them by 2035.

UTC is derived from which reference scale, a weighted average of hundreds of clocks?

International Atomic Time (TAI). Set level with Earth-rotation time in 1958, it has since pulled more than half a minute ahead of UTC, because the planet's spin keeps slowing and atomic clocks do not.

Which crewed outpost runs on UTC because it meets a sunrise or a sunset every 45 minutes?

The International Space Station. With no natural day on board it is locked to a single clock, though crews launched from Baikonur used to arrive still adjusted to Kazakhstan time.

A "sol", about 40 minutes longer than a day on Earth, is a day on which planet?

Mars. Rover controllers have lived on Mars time themselves, starting work about 40 minutes later each day, a rolling jet lag they fought with naps and blue light boxes.

Which South American country kept a half-hour offset, UTC−04:30, from 2007 to 2016?

Venezuela. President Hugo Chávez moved the official meridian by decree in 2007, putting the country half an hour behind its old time until the change was reversed in 2016.

France still keeps UTC+01:00 because of what historical event?

German occupation in World War II. The occupiers put clocks on Berlin time in 1940, and a return to Greenwich time planned after the Liberation was dropped in 1945, so the wartime hour stayed.

Counting its overseas territories, which country spans the most time zones, 12 in all?

France. Its territories stretch from French Polynesia in the eastern Pacific to New Caledonia and Wallis and Futuna beyond the date line; counting its Antarctic claim would make 13.

The International Date Line roughly follows which meridian?

180°. That meridian lies halfway round the world from Greenwich and mostly over open ocean; wherever it would split a country or an island group, the line swerves round, which is why it zigzags.

Crossing the date line eastbound does what to the calendar?

Moves it back one day. That is the twist in Around the World in Eighty Days: travelling east, Phileas Fogg had gained a day without noticing, so he won his bet after all.

Which 1522 voyage first confirmed that circumnavigators lose a day?

Magellan–Elcano expedition. Putting in at Cape Verde after three years sailing west, the survivors found their meticulous log a day behind: it said Wednesday, and the islanders said Thursday.

The Philippines sat a day behind its Asian neighbours for 323 years because of its galleon trade with where?

Acapulco, Mexico. The islands were governed and supplied from Mexico, so they kept the American date until the governor struck 31 December 1844 from the calendar altogether.

Which island pair in the Bering Strait does the date line pass between?

The Diomede Islands. Big Diomede is almost a full day ahead of Little Diomede, a few kilometres to its east, so the pair are nicknamed Tomorrow Island and Yesterday Island.

Which country bent the date line east at the end of 1994 so that all its islands shared one date?

Kiribati. A fifth of its people lived on the far side, so its offices shared only four working days a week; the bulge put its Line Islands on UTC+14:00, the first clock on Earth to reach each new day.

Which Pacific nation skipped Friday 30 December 2011 to jump to the western side of the date line?

Samoa. Being a day behind its main trading partners left only four shared working days a week; it had sat on the American side since 1892, when traders persuaded its king to switch.

Which signal has marked 1 pm at the Royal Observatory, Greenwich, since 1833 so that ships could set their clocks?

A time ball. It drops down a mast on the Observatory roof at exactly one o'clock, a signal ships on the Thames used to set their chronometers; the New Year's Eve ball in Times Square borrows the idea.

Which territory jumped from the Asian to the American side of the date line when the United States acquired it?

Alaska. Its settlers had come from Siberia with the Asian date and the old Julian calendar, twelve days behind, so the handover moved the calendar on by only eleven days.

In 2024 the White House asked NASA to devise a standard time for which place?

The Moon. Weaker gravity makes clocks there run about 58.7 millionths of a second a day faster than on Earth, enough to matter for navigation, so lunar missions are to get a Coordinated Lunar Time of their own.

At which place, where every time zone meets, does a US research station borrow the clock of its distant supply base?

The South Pole. Every meridian meets there, so no zone is the natural one; the station keeps the time of Christchurch, the city its people and supplies fly in from.

William Willett, who campaigned for British daylight saving, was the great-great-grandfather of which rock frontman?

Chris Martin. The Coldplay singer's ancestor is said to have had the idea on an early morning ride, when he noticed how many blinds were still drawn against the daylight.

Port Arthur, the Ontario town that first tried daylight saving in 1908, is now part of which city?

Thunder Bay. Port Arthur's residents put their clocks forward for the summer of 1908, so a small town was saving daylight eight years before any country did.

Which countries were first to adopt daylight saving nationally, on 30 April 1916?

Germany and Austria-Hungary. The aim was to save coal for the war effort, and their enemies copied the idea at once: Britain put its own clocks forward three weeks later.

What kind of piece was Benjamin Franklin's 1784 letter urging Parisians to rise with the sun?

A satire. He proposed taxing window shutters, rationing candles and firing cannon at sunrise to wake the lazy, but he never suggested moving the clocks, so daylight saving is not his invention.

As of 2025, which two US states stay on standard time all year, skipping daylight saving time?

Hawaii and Arizona. Arizona opted out in 1968 because later sunsets only prolonged the desert heat, though the Navajo Nation within the state does change its clocks.

As of 2023, the vast majority of countries that changed their clocks for daylight saving were on which continent?

Europe. Only about a third of the world's countries used it at all; near the equator, where day length barely changes through the year, it gains nobody anything.

Which US law standardised peacetime daylight saving in 1966?

Uniform Time Act. Until then towns and states picked their own dates, and bus passengers on one 35-mile route between West Virginia and Ohio sat through seven time changes.

Which Australian state keeps a half-hour offset, UTC+09:30?

South Australia. Its Central Standard Time also runs in the Northern Territory and, across the state line, in the New South Wales city of Broken Hill, which looks west for its clock, not to Sydney.

Which Australian island shifts its clocks by only 30 minutes for daylight saving?

Lord Howe Island. Its standard time already runs half an hour ahead of Sydney's, so a half-hour summer shift is all it takes to put the island on the mainland's daylight time.

Which US territory lies west of the date line?

Guam. Its clocks run 15 hours ahead of New York's in winter, so Monday morning on the island is still Sunday evening on the East Coast; in all, US law defines nine time zones.

Which family of operating systems counts time in seconds elapsed since midnight UTC on 1 January 1970?

Unix. Linux and macOS inherited the count, and systems that store it in 32 bits will run out of room in January 2038, a deadline known as the Year 2038 problem.

George Hudson proposed modern daylight saving in 1895 because his shift job left evening hours for which hobby?

Collecting insects filled Hudson's after-work hours, so his paper to a Wellington science society asked for a bold two-hour shift rather than one.

Which country's famously late dinners are often blamed on a 1940 move to a time zone an hour too far east?

Spain moved its clocks forward an hour in March 1940 as a temporary wartime step and never moved them back, so the sun over Madrid rises and sets an hour late by the clock.

Which African country with a 13-month calendar also counts clock hours from dawn, so 7 am is one o'clock?

Ethiopia runs two 12-hour cycles that start at dawn and at dusk, so a bus timetabled for 2 o'clock in the local style leaves at what visitors call 8 am.

Which North African country, on permanent summer time from 2018 to 2026, turned its clocks back each Ramadan?

Morocco dropped back to GMT for the holy month and sprang forward again afterwards, a twice-yearly shuffle that ended when the country returned to GMT for good in September 2026.

In which Jules Verne novel does Phileas Fogg win a wager thanks to a calendar quirk?

Around the World in Eighty Days ends with Fogg sure he has lost, until Passepartout discovers the date is a day earlier than their travel diary says.

Which Swiss watch brand launched Internet Time in 1998, dividing the day into 1,000 beats with no time zones?

Swatch sold a line of .beat watches to go with the idea, and each beat lasted just under a minute and a half, so an hour came to roughly 42 of them.

Ruth Belville, London's 'Greenwich Time Lady', earned a living until 1940 by doing what for her clients?

Showing them her watch was a real business: Belville's 1794 pocket chronometer, set at the Royal Observatory, let subscribers correct their own clocks for about £4 a year.

Because Earth turns once every 24 hours, each ideal time zone covers what width of longitude?

15 degrees is the full circle of 360 divided by 24, which is why crossing one ideal zone moves the clock by exactly an hour.

Which North Atlantic country stays on Greenwich Mean Time all year, with no summer clock change?

Iceland fixed its clocks in 1968 on the advice of two of its astronomers, even though the island lies so far west that the sun peaks well after midday.

Which G7 country has gone without daylight saving time since scrapping a postwar experiment in 1952?

Japan had summer time imposed by the Allied authorities in 1948 and abolished it three weeks before they left, and the idea has been debated but never revived.

Countries near which line of latitude rarely use daylight saving, because their day length barely changes?

The Equator sees only small swings in day length, so there is no long summer evening to shift; the case for changing clocks grows the farther from it a country lies.

Which country's clocks ran 20 minutes ahead of Greenwich until 1940, a legacy of its capital's local time?

The Netherlands ran on Amsterdam's own mean time, 19 minutes 32 seconds fast of Greenwich, and tidied it to exactly 20 minutes in 1937, three years before Berlin's hour replaced it.

Before 1916, which capital's official clocks ran 25 minutes behind Greenwich on a time set by Dunsink Observatory?

Dublin Mean Time was the official time of all Ireland from 1880, and it took the Time (Ireland) Act of 1916 to bring the island's clocks into line with Britain's.

Which Middle Eastern country keeps the half-hour offset UTC+03:30 and abolished daylight saving in 2022?

Iran sets its clocks by the line 52.5 degrees east, the same one that anchors the Iranian calendar, which falls exactly halfway between two hourly zones.

Which Southeast Asian country moved its clocks forward half an hour at the end of 1981 to match Malaysia?

Singapore made the jump at 11:30 pm on New Year's Eve, cutting the last night of 1981 short, after Malaysia put all of its territory on UTC+08:00.

Which Southeast Asian country's three time zones are known by the abbreviations WIB, WITA and WIT?

Indonesia is so wide that Sumatra and Java run two hours behind Western New Guinea, with Bali and Sulawesi in the middle zone.

Which Australian state voted down daylight saving at a 1992 referendum that followed a three-year trial?

Queensland split by geography: the south-east around Brisbane wanted the lighter evenings, but the north and west voted no and carried the day with 54.5 per cent.

Under a Time Act passed in 1966, most of which Canadian province keeps the same clock time all year?

Saskatchewan hired an astronomer to sort out a patchwork of towns keeping different times, though the border city of Lloydminster went on changing its clocks to match Alberta.

Which Mediterranean country decided in 2016 to stay on summer time all year, fixing its clocks at UTC+03:00?

Turkey announced in 2017 that it would go back to changing its clocks, reversed course within weeks, and a presidential decree in 2018 confirmed UTC+03:00 as permanent.

Which South American country abolished daylight saving time in 2019 after using it every summer since 1985?

Brazil long set its start and end dates by decree, and the rules even pushed the change back a week whenever it would otherwise have landed on carnival.

Earth's spin in which direction makes the Sun rise over Sydney hours before it rises over London?

West to east is the way the planet turns, so places farther east always meet the morning first; seen from above the northern end of its axis, Earth spins counterclockwise.

Which kind of day, about four minutes shorter than a solar day, measures Earth's spin against the distant stars?

Sidereal day is the astronomers' term: Earth must turn a little extra to face the Sun again, so it spins about 366 times against the stars in a 365-day year.

What name is given to the figure-eight the Sun traces when photographed at the same clock time all year?

Analemma loops are tall because the Sun climbs and sinks with the seasons, and wide because the Sun's own time drifts ahead of clock time and then behind it over the year.

Which feature of Earth makes summer days longer than winter ones, the difference daylight saving time exploits?

Its axial tilt of about 23.4 degrees leans each half of the planet toward the Sun for part of the year, and more than half of every day there is then spent in daylight.

What is gradually slowing Earth's spin, adding roughly two milliseconds to the length of a day every century?

Tidal friction comes from the ocean bulges dragging on the turning planet, a slowdown Delaunay and Ferrel each proposed in the 1860s to explain a puzzle in the Moon's motion.

What do astronomers call the moving line that separates Earth's daylit side from its night side?

The terminator is blurred into twilight by the atmosphere, and it crawls ever more slowly toward the far north and south, where it can stall for a full day of sun or dark.

Flying quickly across several time zones throws which internal body cycle out of step, causing jet lag?

Circadian rhythm resets by roughly an hour of time difference per day, so a trip across six zones can leave a traveller out of sorts for most of a week.

Vibrations of which metal's atoms have defined the length of a second since 1967, anchoring the world's clocks?

Caesium atoms tick 9,192,631,770 times in one second, a figure picked to match the older second that astronomers had measured from Earth's orbit.

Which English clockmaker's sea-going timekeepers let sailors work out longitude by carrying home-port time with them?

John Harrison, a joiner by trade, cracked a problem that Parliament had put a £20,000 reward on, and he was 80 before its final payment came, after King George III took up his cause.

Countries in which hemisphere put clocks forward around September or October and back around March or April?

Southern countries such as Chile and Australia have their spring while the north has its autumn, so their daylight saving calendar runs roughly in reverse.

Which city hosted the 1884 conference where delegates voted 22 to 1 to count longitude from Greenwich?

Washington hosted at the request of President Chester Arthur, and the only vote against Greenwich came from San Domingo, the country now called the Dominican Republic.

The telescope that fixed the Greenwich line of zero longitude in 1851 is named after which Astronomer Royal?

George Airy set up his transit circle in 1851, yet satellite navigation now puts zero longitude about 102 metres east of the marked line that visitors straddle.

Astronomers long began each Greenwich Mean Time day at which moment, a convention dating back to Ptolemy?

Noon was hour zero for astronomers, which left them half a day out of step with everyone else's GMT and makes old Greenwich times ambiguous without context.

Which university city's Great Tom bell rings at 9:05 pm because local time there once ran five minutes behind Greenwich?

Oxford hears the bell 101 times a night, once for each of Christ Church's original scholars plus one added in 1663, and it used to tell every college to lock its gates.

What nickname do BBC radio listeners give the six short tones of the hourly Greenwich Time Signal?

The pips count down the last five seconds of the hour, and the sixth, which lands on the hour itself, has been longer than the rest since 1972.

Which three-letter abbreviation names the United Kingdom's clock time when it runs an hour ahead of GMT?

BST, short for British Summer Time, starts at 1 am GMT on a spring morning, taking an hour of light from the start of the day and adding it to the evening.

The first national daylight saving schemes of 1916 were wartime measures meant to conserve which fuel?

Coal was running short in wartime, and lighter evenings were meant to ease the squeeze; Britain and most of its allies soon copied the idea.

Which West African country kept its clocks 44 minutes 30 seconds behind Greenwich until January 1972?

Liberia ran on Monrovia Mean Time, set by the longitude of its capital, and had even nudged it by 1 minute 22 seconds in 1919 before finally adopting GMT.

Which uninhabited Pacific island, never reached by Amelia Earhart in 1937, lies in Earth's last time zone, UTC−12:00?

Howland and its neighbour Baker are the only land in the zone, so every calendar date makes its final appearance over two empty nature reserves.

Before Greenwich, many maps counted longitude from which Canary Island, the supposed western edge of the Old World?

El Hierro, or Ferro to mapmakers, was picked by Louis XIII and Cardinal Richelieu in 1634, echoing Ptolemy's idea of a zero line at the edge of the known world.

In the lettered military time zone system, which letter is skipped as a zone and can instead mean local time?

J, spoken as Juliett, belongs to no zone at all, so a time marked with it simply means the clock wherever the observer happens to be.

The tz database behind every phone's time zone rules is sometimes named after which founding contributor?

Olson, in full Arthur David Olson, gave the volunteer project its nickname, while its place-based zone names such as America/New_York were designed by Paul Eggert.

Which remote Pacific island group keeps its own time zone, UTC+12:45, exactly 45 minutes ahead of its mainland?

Chatham Islands clocks keep the three-quarter-hour gap all year, so their daylight saving change happens at the odd time of 2:45 in the morning.

Which vast Central Asian country merged its two time zones into one, UTC+05:00, in March 2024?

Kazakhstan made the switch at midnight on 1 March 2024, and a petition called Turn the Time Back soon gathered enough votes to force an official review.

Which island nation returned to UTC+05:30 in 2006, ending a decade on other offsets?

Sri Lanka had pushed its clocks forward during a severe power shortage in 1996, but areas held by the Tamil Tigers never went along, leaving the island on two times.

Clocks in London, Rome and New York all change for daylight saving in the small hours of which day?

Sunday was chosen so that the change falls on a weekend night, when it disrupts the fewest timetables, shifts and opening hours.

Which ancient timekeeper reads a time true only for its own longitude, so it can disagree with a zone clock?

A sundial needs three corrections to match a zone clock: for summer time, for longitude within the zone, and for the Sun's own unevenness, which alone can reach 16 minutes.

Which Southeast Asian country keeps the half-hour offset UTC+06:30, thirty minutes behind neighbouring Thailand?

Myanmar has never used daylight saving, and its odd half hour goes back to 1905, when colonial Burma fixed a standard time on the longitude 97°30' east.

Roadhouses along which Australian highway across the Nullarbor Plain keep their own unofficial time, UTC+08:45?

Eyre Highway is named for Edward John Eyre, the first European to cross the Nullarbor by land in 1840-41, and stops such as Eucla and Madura keep what locals call Central Western Time.

Which king founded the Royal Observatory at Greenwich in 1675, hoping astronomers could help sailors find longitude?

Charles II also created the post of Astronomer Royal that year, with orders to perfect the star tables that navigators needed to fix their position at sea.