Standard time is the result of synchronizing clocks in different geographical locations within a
time zoneA time zone is a region of the earth that has uniform standard time, usually referred to as the local time. By convention, time zones compute their local time as an offset from UTC . Local time is UTC plus the current time zone offset for the considered location.-Introduction:Time zones are...
to the same time rather than using the local
meridianA meridian is an imaginary arc on the Earth's surface from the North Pole to the South Pole that connects all locations running along it with a given longitude. The position of a point on the meridian is given by the latitude. Each meridian is perpendicular to all circles of latitude at the...
as in
local mean timeLocal mean time is a form of solar time that corrects the variations of local apparent time, forming a uniform time scale at a specific longitude...
or
solar timeSolar times are measures of the apparent position of the Sun on the celestial sphere. They are not actually the physical time, but rather hour angles, that is, angles expressed in time units...
. The time so set has come to be defined in terms of offsets from
Universal TimeUniversal Time is a timescale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the meridian of Greenwich, and GMT is sometimes used loosely as a synonym for UTC. In fact the expression "Universal Time" is ambiguous, as there are...
. (See more about standard time.)
Where
daylight saving timeDaylight saving time is the convention of advancing clocks so that afternoons have more daylight and mornings have less. Typically clocks are adjusted forward one hour near the start of spring and are adjusted backward in autumn...
is used, "standard time" may refer to the time without daylight saving time.
A standardized time system was first used by British railways on December 11, 1847, when they switched from local mean time to GMT.
Standard time is the result of synchronizing clocks in different geographical locations within a
time zoneA time zone is a region of the earth that has uniform standard time, usually referred to as the local time. By convention, time zones compute their local time as an offset from UTC . Local time is UTC plus the current time zone offset for the considered location.-Introduction:Time zones are...
to the same time rather than using the local
meridianA meridian is an imaginary arc on the Earth's surface from the North Pole to the South Pole that connects all locations running along it with a given longitude. The position of a point on the meridian is given by the latitude. Each meridian is perpendicular to all circles of latitude at the...
as in
local mean timeLocal mean time is a form of solar time that corrects the variations of local apparent time, forming a uniform time scale at a specific longitude...
or
solar timeSolar times are measures of the apparent position of the Sun on the celestial sphere. They are not actually the physical time, but rather hour angles, that is, angles expressed in time units...
. The time so set has come to be defined in terms of offsets from
Universal TimeUniversal Time is a timescale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the meridian of Greenwich, and GMT is sometimes used loosely as a synonym for UTC. In fact the expression "Universal Time" is ambiguous, as there are...
. (See more about standard time.)
Where
daylight saving timeDaylight saving time is the convention of advancing clocks so that afternoons have more daylight and mornings have less. Typically clocks are adjusted forward one hour near the start of spring and are adjusted backward in autumn...
is used, "standard time" may refer to the time without daylight saving time.
Great Britain
A standardized time system was first used by British railways on December 11, 1847, when they switched from local mean time to GMT. It was also given the name
Railway timeRailway time was the name given to the standardised time arrangement first applied by the Great Western Railway in England in November 1840. This was the first recorded occasion when a number of different local times were synchronised and a single standard time applied...
reflecting the important role the railway companies played in bringing it about. The vast majority of
Great BritainGreat Britain is an island lying to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island. With a population of about 59.6 million people, it is the third most populated island on Earth. Great Britain is surrounded by over 1000 smaller...
's public clocks were being synchronised using GMT by 1855.
North America
Prior to 1883, local mean time was used throughout
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
, resulting in an inordinate number of local times. This caused convoluted regional and national
trainA train is a connected series of vehicles for rail transport that move along a track to transport freight or passengers from one place to another. The track usually consists of two rails, but might also be a monorail or maglev guideway....
schedules.
Sandford FlemingSir Sandford Fleming was a Scottish-born Canadian engineer and inventor, known for proposing worldwide standard time zones, Canada's postage stamp, a huge body of surveying and map making, engineering much of the Intercolonial Railway and the Canadian Pacific Railway, and being a founding member...
, a
CanadianCanada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean...
, proposed Standard Time at a meeting of the
Royal Canadian InstituteThe Royal Canadian Institute, or RCI, is an organization dedicated to the advancement of science.First formed in 1849 by Sir Sandford Fleming, it was incorporated in 1851, and is today the oldest scientific society in Canada....
on February 8 1879. On October 11, 1883, the heads of the major railroads met in
ChicagoChicago is the largest city in the U.S. state of Illinois, and with more than 2.8 million people, the 3rd largest city in the United States...
at the former
Grand Pacific Hotel-United States:* Grand Pacific Hotel , Illinois* Grand Pacific Hotel , listed on the National Register of Historic Places in Montana* Grand Pacific Hotel , listed on the NRHP in Ohio...
to adopt the Standard Time System. The new system was adopted by most states almost immediately after railroads did so and finally officially adopted by the U.S. government almost fifty years later.
In 2007 the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
enacted a federal law formalizing the use of
Coordinated Universal TimeCoordinated Universal Time , ) is a time standard based on International Atomic Time with leap seconds added at irregular intervals to compensate for the Earth's slowing rotation...
as the basis of standard time, and the role of the Secretary of Commerce (effectively, the
National Institute of Standards and TechnologyThe National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory which is a non-regulatory agency of the United States Department of Commerce...
) and the
Secretary of the NavyThe United States Navy is the sea branch of the U.S. Armed Forces. It is one of the seven uniformed services of the United States. As of 31 December 2008, the U.S. Navy had about 331,682 personnel on active duty and 124,000 in the Navy Reserve. It operates 283 ships in active service and more than...
(effectively, the
U.S. Naval ObservatoryThe United States Naval Observatory is one of the oldest scientific agencies in the United States, with a primary mission to produce Positioning, Navigation, and Timing for the U.S. Navy and the U.S. Department of Defense...
) in interpreting standard time.