47 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.