50 Fun Facts About Time Zones

What is the full range of standard UTC offsets in use around the world?

Most offsets are whole hours, but a few zones add 30 or 45 minutes, as in India and Nepal.

Solar time shifts by how much for every degree of longitude?

That is why solar noon in Bristol comes about ten minutes after London's; Bristol lies 2.5 degrees west.

Which British rail company began using Greenwich Mean Time in November 1840?

Portable chronometers carried the time; other companies followed and it became known as "railway time".

When did GMT become the legal time for Great Britain?

By 1855 some 98 per cent of public clocks already showed it; some clocks had two minute hands, one local and one GMT.

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

It was based on longitude 172°30′ east and called New Zealand Mean Time.

Which US meteorologist divided the country into four zones for his weather stations?

His 1879 Report on Standard Time helped persuade the railroads in 1883 and, eventually, the US government.

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

Station clocks were reset as standard-time noon arrived in each zone; the zones were drawn through stations in major cities.

Which US city kept local time until 1900 and only settled on Eastern Time in 1915?

It lies about halfway between the Eastern and Central meridians and tried Central, local mean and Eastern time in turn.

In which year did the US Congress formally adopt standard time zones?

The Standard Time Act of March 19, 1918, also introduced daylight saving as a wartime measure.

Who proposed a worldwide system of 24 time zones in 1876?

The Scottish-born Canadian labelled his zones A to Y, skipping J; each covered 15 degrees of longitude.

Which Italian mathematician first floated worldwide time zones in an 1858 book?

His book Miranda! proposed 24 "longitudinal days" centred on Rome, but attracted no attention until long after his death.

Which country was the last to adopt a standard offset, moving to UTC+05:45 in 1986?

It had used Indian Standard Time since 1920, then advanced its clocks by 15 minutes.

How many time zones does Russia have?

Two were removed in 2010 and restored in 2014; about 63 per cent of Russians live on Moscow time.

China spans five geographic time zones but officially observes how many?

It is the largest country to do so; in far-western Xinjiang solar noon can fall as late as 15:00 Beijing time.

Xinjiang's unofficial local clock, two hours behind Beijing, is named for which city?

Offices there commonly open at 10:00 Beijing time, which is 08:00 locally; TV channels are scheduled by ethnicity.

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

You step from UTC+04:30 to UTC+08:00 at the Wakhjir Pass.

What is the UTC offset of Indian Standard Time?

It was adopted in 1906; Kolkata and Mumbai kept their own local times until 1948 and 1955.

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

The sun rises almost two hours earlier on India's eastern border than in the far west, yet the country keeps one zone.

What is the letter designation for the zero-UTC-offset zone, giving it its nickname?

Greenwich was the point of origin of the lettered zones; pilots everywhere file flight plans in Zulu.

Why is Coordinated Universal Time abbreviated UTC rather than CUT?

The ITU and IAU wanted one abbreviation everywhere; UTC also fits the pattern of UT0, UT1 and UT2.

Leap seconds were first added to UTC in which year?

They keep UTC within 0.9 seconds of Earth's rotation; a 2022 resolution aims to abolish them by 2035.

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

TAI is a weighted average of hundreds of atomic clocks; GPS time runs exactly 19 seconds behind it.

Which time standard does the International Space Station normally keep?

Orbiting crews see many sunrises a day, so missions usually run on the launch site's or mission control's time.

A Martian solar day, used by some rover teams, is called what and how long is it?

Earth controllers for solar-powered rovers have synchronised their sleep cycles to the Martian day.

Which year did France officially adopt GMT+0 as its time, after decades on Paris time?

Paris mean time ran 9 minutes 21 seconds ahead of Greenwich; the railways had lagged it by a further five minutes for latecomers.

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

The Netherlands had run on "Amsterdam Time", 20 minutes ahead of GMT, before being forced onto German time as well.

With its overseas territories, France spans how many time zones, the most of any country?

Thirteen if you count its claim in Antarctica; every overseas territory runs on a different zone from Paris.

The International Date Line roughly follows which meridian?

It is a cartographic convention, not international law, so countries have moved it for convenience.

Crossing the date line eastbound does what to the calendar?

Westbound travellers skip forward a day; Magellan's crew discovered the effect in 1522.

Which 1522 voyage first confirmed that circumnavigators lose a day?

At Cape Verde the crew thought it was Wednesday 9 July; locals told them it was Thursday 10 July.

The Philippines sat a day behind its Asian neighbours for 323 years due to trade with where?

As part of New Spain it sat east of the date line until 30 December 1844.

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

The line runs 1.5 km from each island, one Russian and one American.

Which country moved the date line east in 1994 so its whole territory shared one date?

Its Line Islands jumped from UTC−10:00 to UTC+14:00, a zone that had not existed before.

What is the most advanced time zone in the world?

Kiribati's Line Islands, including Kiritimati, greeted the year 2000 before anywhere else on Earth.

Which date did Samoa delete from its calendar when it jumped west of the date line?

Being 21 hours behind Australia and New Zealand left only four shared workdays a week.

Which territory crossed the date line alongside Samoa in 2011?

Its links to the world run through Samoa; strictly it jumped an hour later because it kept no summer time.

When the US bought Alaska in 1867, what happened to its calendar?

Russian settlers had arrived from Siberia; the transfer ceremony fell on 7 October (Julian) and 19 October (Gregorian).

For how long each day are three different calendar dates in use on Earth?

From 10:00 to 12:00 UTC it is one day on Baker Island, the next almost everywhere, and the one after in Kiritimati.

Who made the first realistic proposal for daylight saving, in 1895?

The New Zealand entomologist wanted two more hours of evening light to collect insects.

Which English builder independently proposed daylight saving in 1907 after an early ride?

An avid golfer, he hated cutting rounds short at dusk; Parliament narrowly rejected his bill in 1909.

Which twin Ontario cities were the first in the world to enact daylight saving, in 1908?

Orillia followed under mayor William Sword Frost in 1911–12.

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

The aim was to conserve coal in wartime; Britain followed on 21 May 1916 and the US in 1918.

Benjamin Franklin's 1784 letter about Parisians waking earlier was actually what?

He suggested taxing shutters, rationing candles and firing cannons at sunrise, but never proposed moving clocks.

Which two US states do not observe daylight saving time?

Within Arizona the Navajo Nation does observe it, while the Hopi Nation inside the Navajo Nation does not.

Roughly what share of the world's countries used daylight saving time as of 2023?

It is mostly a European and North American habit; equatorial countries gain little from it.

Which US law standardised peacetime daylight saving in 1966?

In 1965 St. Paul and Minneapolis had kept different clocks for two weeks because they disagreed on the start date.

Which Australian state uses a half-hour offset, UTC+09:30, after lobbying by cricketers?

It advanced Central Standard Time by 30 minutes in 1899; attempts to undo it in 1986 and 1994 failed.

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

Everywhere else that observes DST moves a full hour.

How many standard time zones cover the US states and territories?

Four cover the contiguous states; the rest reach from Puerto Rico to Guam and American Samoa.

Unix time counts seconds from midnight UTC on which date?

Leap seconds are excluded; Windows instead counts 100-nanosecond units from 1601.