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"Timezone" and "TimeZone" redirect here. For other uses, see Time zone (disambiguation).
For detailed information on all time zones, see List of time zones. This is a list of Time zones sorted by Time offsets from Coordinated Universal Time (UTC

A time zone is a region of the Earth that has adopted the same standard time, usually referred to as the local time. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Standard time is the result of synchronizing clocks in different geographical locations within a Time zone to the same time rather than using the local meridian as Most adjacent time zones are exactly one hour apart, and by convention compute their local time as an offset from UTC (see also Greenwich Mean Time). Greenwich Mean Time ( GMT) is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London

Standard time zones can be defined by geometrically subdividing the Earth's spheroid into 24 lunes (wedge-shaped sections), bordered by meridians each 15° of longitude apart. Equation A spheroid centered at the origin and rotated about the z axis is defined by the implicit equation \left(\frac{x}{a}\right^2+\left(\frac{y}{a}\right^2+\left(\frac{z}{b}\right^2 A lune is either of two figures both shaped roughly like a crescent Moon. This article is about the geographical concept For other uses of the word see Meridian. Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement The local time in neighbouring zones would differ by one hour. However, political and geographical practicalities can result in irregularly-shaped zones that follow political boundaries or that change their time seasonally (as with daylight saving time), as well as being subject to occasional redefinition as political conditions change. Daylight saving time ( DST

Before the adoption of time zones, people used local solar time (originally apparent solar time, as with a sundial; and, later, mean solar time). Solar times are measures of the apparent position of the Sun on the Celestial sphere. A sundial is a device that measures time by the position of the Sun. Mean solar time is the average over a year of apparent solar time. Its difference from apparent solar time is the equation of time. The equation of time is the difference over the course of a year between time as read from a Sundial and time as read from a Clock, measured in an ideal situation

This became increasingly awkward as railways and telecommunications improved, because clocks differed between places by an amount corresponding to the difference in their geographical longitude, which was usually not a convenient number. "Railroad" and "Railway" both redirect here For other uses see Railroad (disambiguation. This problem could be solved by synchronizing the clocks in all localities, but then in many places the local time would differ markedly from the solar time to which people are accustomed. Time zones are thus a compromise, relaxing the complex geographic dependence while still allowing local time to approximate the mean solar time. There has been a general trend to push the boundaries of time zones further west of their designated meridians in order to create a permanent daylight saving time effect. Daylight saving time ( DST The increase in worldwide communication has further increased the need for interacting parties to communicate mutually comprehensible time references to one another.

Contents

Standard time zones

Standard time zones of the world as of June 2008.
Standard time zones of the world as of June 2008.

Earlier, time zones based their time on Greenwich Mean Time (GMT, also called UT1), the mean solar time at longitude 0° (the Prime Meridian). The Prime Meridian is the meridian (line of Longitude) at which longitude is defined to be 0° But as a mean solar time, GMT is defined by the rotation of the Earth, which is not constant in rate. So, the rate of atomic clocks was annually changed or steered to closely match GMT. An atomic clock is a type of Clock that uses an Atomic resonance Frequency standard as its timekeeping element But on January 1, 1972 it became fixed, using predefined leap seconds instead of rate changes. New Year See also New Year The Ancient Romans began their consular year on January 1st since 153 BC Year 1972 ( MCMLXXII) was a Leap year starting on Saturday (link will display full calendar of the Gregorian calendar. A leap second is a one- Second adjustment that keeps broadcast standards for time of day close to mean solar time. This new time system is Coordinated Universal Time (UTC). Leap seconds are inserted to keep UTC within 0. 9 seconds of UT1. In this way, local times continue to correspond approximately to mean solar time, while the effects of variations in Earth's rotation rate are confined to simple step changes that can be easily subtracted if a uniform time scale (International Atomic Time or TAI) is desired. International Atomic Time ( TAI, from the French name Temps Atomique International) is a high-precision atomic Time standard that tracks With the implementation of UTC, nations began to use it in the definition of their time zones instead of GMT. As of 2005, most but not all nations have altered the definition of local time in this way (though many media outlets fail to make a distinction between GMT and UTC). Further change to the basis of time zones may occur if proposals to abandon leap seconds succeed.

Due to daylight saving time, UTC is local time at the Royal Observatory, Greenwich only between 01:00 UTC on the last Sunday in October and 01:00 UTC on the last Sunday in March. Daylight saving time ( DST The Royal Observatory Greenwich (formerly the Royal Greenwich Observatory or RGO) was commissioned in 1675 by King Charles II, with the For the rest of the year, local time there is UTC+1, known in the United Kingdom as British Summer Time (BST). UTC+1 is used in the following locations Central European Time West Africa Time Western European Summer Time The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Western European Summer Time ( WEST) is a summer Daylight saving time scheme 1 hour ahead of Coordinated Universal Time. Similar circumstances apply in many places.

The definition for time zones can be written in short form as UTC±n (or GMT±n), where n is the offset in hours. These examples give the local time at various locations at 12:00 UTC when daylight saving time (or summer time, etc. ) is not in effect:

Where the adjustment for time zones results in a time at the other side of midnight from UTC, then the date at the location is one day later or earlier. Los Angeles (lɑˈsændʒələs los ˈaŋxeles in Spanish) is the largest City in the state of California and the American West California ( is a US state on the West Coast of the United States, along the Pacific Ocean. The United States of America —commonly referred to as the UTC−8 is a band of Timezones separated from the Universal Coordinated Time by 8 hours Saint John is the largest city in the Province of New Brunswick, and the oldest incorporated city in Canada. Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page UTC−4 is the Time offset used in the Atlantic Standard Time Zone in Canada in winter and the North American Eastern Time Zone during The City of New York New York ( is a state in the Mid-Atlantic and Northeastern regions of the United States and is the nation's third most populous The United States of America —commonly referred to as the UTC−5 is the Time offset used in the North American Eastern Time Zone during Standard time and in the North American Central Time Zone during Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city This article is about the country For a topic outline on this subject see List of basic France topics. UTC+1 is used in the following locations Central European Time West Africa Time Western European Summer Time Cape Town (Kaapstad Xhosa: Ikapa) is the second most populous city in South Africa, forming part of the metropolitan municipality of the The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa UTC+2 corresponds to the following Time zones Eastern European Time Egypt Standard Time Central Africa Time New Delhi (नई दिल्ली ਨਵੀਂ ਦਿੱਲੀ نئی دلی is the Capital city of India. India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country UTC+530 is the Timezone for Indian Standard Time Sri Lanka Time Jakarta (also DKI Jakarta) is the Capital and largest city of Indonesia. The Republic of Indonesia ( (Republik Indonesia is a Country in Southeast Asia. UTC+7 is a Time zone used in Laos Thailand Cambodia Vietnam Seoul ( soʊl is the Capital and largest City of South Korea. Korea is a geographic area composed of two sovereign countries a civilization and a former state situated on the Korean Peninsula in East Asia. UTC+9 is a Time zone used for the following locations Single-zone Countries East Timor Japan (JST— Japan Melbourne ( is the second most populous city in Australia, with a Metropolitan area population of approximately 3 For a topic outline on this subject see List of basic Australia topics. The UTC+10 Time zone covers the following locations Australia (AEST&mdash Australian Eastern Standard Time) Australian Some examples when UTC is 23:00 on Monday when daylight saving time is not in effect:

Some examples when UTC is 02:00 on Tuesday when daylight saving time is not in effect:

The time-zone adjustment for a specific location may vary because of daylight saving time. Cairo () which means "the Vanquisher" or "the Triumphant" is the capital and largest city of Egypt. This article is about the country of Egypt For a topic outline on this subject see List of basic Egypt topics. Wellington (ˈwælɪŋtən is the Capital of New Zealand, the country's second largest urban area, the New Zealand is an Island country in the south-western Pacific Ocean comprising two main landmasses (the North Island and the South Island UTC+12 is a Time zone for the following locations Fiji Gilbert Islands, Kiribati Marshall Islands The City of New York New York ( is a state in the Mid-Atlantic and Northeastern regions of the United States and is the nation's third most populous UTC−5 is the Time offset used in the North American Eastern Time Zone during Standard time and in the North American Central Time Zone during Honolulu is the Capital and most populous Census-designated place (CDP in the U The State of Hawaii ( or həˈwaɪʔiː Hawaiian: Mokuāina o Hawaii) is a state in the United States located on an Archipelago in the The UTC−10 Time offset is used in Cook Islands French Polynesia Society Archipelago including For example New Zealand, which is usually UTC+12, observes a one-hour daylight saving time adjustment during the southern hemisphere summer, resulting in a local time of UTC+13. UTC+12 is a Time zone for the following locations Fiji Gilbert Islands, Kiribati Marshall Islands Southern Hemisphere is the half of a Planet that is South of the Equator —the word hemisphere literally means 'half ball' UTC+13 is a Time zone for the following locations Enderbury Kiribati (Phoenix Islands Time New Zealand Daylight Time

See also: Sidereal time

History

Greenwich Mean Time (GMT) was established in 1675 when the Royal Observatory was built, as an aid to determine longitude at sea by mariners. Sidereal time is a measure of the position of the Earth in its rotation around its axis or time measured by the apparent Diurnal motion of the Vernal equinox Greenwich Mean Time ( GMT) is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London The Royal Observatory Greenwich (formerly the Royal Greenwich Observatory or RGO) was commissioned in 1675 by King Charles II, with the The first time zone in the world was established by British railways on December 1, 1847 — with GMT hand-carried on chronometers. "Railroad" and "Railway" both redirect here For other uses see Railroad (disambiguation. Events 800 - Charlemagne judges the accusations against Pope Leo III in the Vatican Year 1847 ( MDCCCXLVII) was a Common year starting on Friday (link will display the full calendar of the Gregorian Calendar (or a Common A marine chronometer is a timekeeper precise enough to be used as a portable Time standard; it can therefore be used to determine Longitude by means of Celestial This quickly became known as Railway Time. Railway time was the name given to the standardised time arrangement first applied by the Great Western Railway in England in November 1840 About August 23, 1852, time signals were first transmitted by telegraph from the Royal Observatory, Greenwich. Events 79 - Mount Vesuvius begins stirring on the feast day of Vulcan the Roman god of fire Year 1852 ( MDCCCLII) was a Leap year starting on Thursday (link will display the full calendar of the Gregorian calendar (or a Leap year The Royal Observatory Greenwich (formerly the Royal Greenwich Observatory or RGO) was commissioned in 1675 by King Charles II, with the Even though 98% of Great Britain's public clocks were using GMT by 1855, it was not made Britain's legal time until August 2, 1880. See also Kingdom of Great Britain Great Britain (Breatainn Mhòr Prydain Fawr Breten Veur Graet Breetain is the larger of the two main islands Events 338 BC - A Macedonian army led by Philip II defeated the combined forces of Athens and Thebes in the Year 1880 ( MDCCCLXXX) was a Leap year starting on Thursday (link will display the full calendar of the Gregorian calendar (or a Leap year Some old clocks from this period have two minute hands — one for the local time, one for GMT. [1] This only applied to the island of Great Britain, and not to the island of Ireland. Ireland (pronounced /ˈaɾlənd/ Éire) is the third largest island in Europe, and the twentieth-largest island in the world

On November 2, 1868, New Zealand (then a British colony) officially adopted a standard time to be observed throughout the colony, and was perhaps the first country to do so. Events 1570 - A Tidal wave in the North Sea devastates the coast from Holland to Jutland, killing more than 1000 Year 1868 ( MDCCCLXVIII) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian Calendar (or a Leap New Zealand is an Island country in the south-western Pacific Ocean comprising two main landmasses (the North Island and the South Island It was based on the longitude 172°30′ East of Greenwich, that is 11 hours 30 minutes ahead of GMT. Greenwich ( ˈɡrɛnɪtʃ GREN-itch /ˈɡrɛnɪdʒ/ GREN-idge or /ˈɡrɪnɪdʒ/ GRIN-idge is a district in south-east London, This standard was known as New Zealand Mean Time. History On 2 November 1868, New Zealand officially adopted a standard time to be observed nationally and was perhaps the first country to do so

Timekeeping on the American railroads in the mid nineteenth century was somewhat confused. Each railroad used its own standard time, usually based on the local time of its headquarters or most important terminus, and the railroad's train schedules were published using its own time. Some major railroad junctions served by several different railroads had a separate clock for each railroad, each showing a different time; the main station in Pittsburgh, Pennsylvania, for example, kept six different times. The Commonwealth of Pennsylvania ( often colloquially referred to as PA (its abbreviation by natives and Northeasterners is a state located in the Northeastern The confusion for travelers making a long journey involving several changes of train can be imagined.

Charles F. Dowd proposed a system of one-hour standard time zones for American railroads about 1863, although he published nothing on the matter at that time and did not consult railroad officials until 1869. Charles F Dowd (1825&ndash1904 was a co-principal (with his wife Harriet M In 1870, he proposed four ideal time zones (having north–south borders), the first centered on Washington, D.C., but by 1872 the first was centered 75°W of Greenwich, with geographic borders (for example, sections of the Appalachian Mountains). Washington DC ( formally the District of Columbia and commonly referred to as Washington, the District, or simply D The Appalachian Mountains ( often called the Appalachians, are a vast system of mountains in eastern North America. Dowd's system was never accepted by American railroads. Instead, U. S. and Canadian railroads implemented a version proposed William F. Allen, the editor of the Traveler's Official Railway Guide. [2] The borders of its time zones ran through railroad stations, often in major cities. For example, the border between its Eastern and Central time zones ran through Detroit, Buffalo, Pittsburgh, Atlanta, and Charleston. Buffalo (ˈbʌfəloʊ is the second largest city in New York State. Charleston is a city in Charleston county in the US state of South Carolina. It was adopted on Sunday, November 18, 1883, also called "The Day of Two Noons", when each railroad station clock was reset as standard-time noon was reached within each time zone. Events 326 - The old St Peter's Basilica is consecrated 1302 - Pope Boniface VIII issues the Papal bull Year 1883 ( MDCCCLXXXIII) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common The zones were named Intercolonial, Eastern, Central, Mountain, and Pacific. Within one year, 85% of all cities with populations over 10,000, about 200 cities, were using standard time. A notable exception was Detroit (which is about half-way between the meridians of eastern time and central time), which kept local time until 1900, then tried Central Standard Time, local mean time, and Eastern Standard Time before a May 1915 ordinance settled on EST and was ratified by popular vote in August 1916. Local 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 The Eastern Time Zone ( ET) of the Western Hemisphere falls mostly along the east coast of North America and the west coast of South America This hodgepodge ended when Standard zone time was formally adopted by the U.S. Congress on 19 March 1918 as the Standard Time Act. The United States Congress is the bicameral Legislature of the federal government of the United States of America, consisting of two houses Events 1279 - A Mongolian victory in the Battle of Yamen ends the Song Dynasty in China. Year 1918 ( MCMXVIII) was a Common year starting on Tuesday (link will display the full calendar of the Gregorian calendar (or a Common

Time zones were first proposed for the entire world by Canada's Sir Sandford Fleming in 1876 as an appendage to the single 24-hour clock he proposed for the entire world (located at the center of the Earth and not linked to any surface meridian). Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page Sir Sandford Fleming (January 7 1827 – July 22 1915 was a prolific Scottish-born Canadian Engineer and Inventor, known for introducing Universal In 1879 he specified that his universal day would begin at the anti-meridian of Greenwich (now called 180°), while conceding that hourly time zones might have some limited local use. He continued to advocate his system at subsequent international conferences. In October 1884, the International Meridian Conference did not adopt his time zones because they were not within its purview. The International Meridian Conference was a conference held in October 1884 in Washington D The conference did adopt a universal day of 24 hours beginning at Greenwich midnight, but specified that it "shall not interfere with the use of local or standard time where desirable".

Nevertheless, most major countries had adopted hourly time zones by 1929. Today, all nations use standard time zones for secular purposes, but they do not all apply the concept as originally conceived. Newfoundland, India, Iran, Afghanistan, Venezuela, Burma, the Marquesas, as well as parts of Australia use half-hour deviations from standard time, and some nations, such as Nepal, and some provinces, such as the Chatham Islands, use quarter-hour deviations. Newfoundland and Labrador (ˈnuːfɨn(dlənd ən(d ˈlæbrəˌdɔr (Terre-Neuve-et-Labrador is a province of Canada, the tenth and latest to join the Confederation Nepal (नेपाल) is a Landlocked country in South Asia. The Archipelago of the Chatham Islands ( Rekohu in the Moriori language and Wharekauri in the Māori language) is a territory Some countries, most notably China, use a single timezone even though the extent of their territory far exceeds 15° of longitude. Talk People's Republic of China) PEOPLE'S REPUBLIC OF CHINA ARTICLE GUIDELINES

Nautical time zones

Main article: Nautical time

Since the 1920s a nautical standard time system has been in operation for ships on the high seas. The establishment of nautical standard times, nautical standard time zones and the nautical date line were recommended by the Anglo-French Conference on Time-keeping The establishment of nautical standard times, nautical standard time zones and the nautical date line were recommended by the Anglo-French Conference on Time-keeping International waterways Several international treaties have established freedom of navigation on semi-enclosed seas Nautical time zones are an ideal form of the terrestrial time zone system. Under the system, a time change of one hour is required for each change of longitude by 15°. Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement The 15° gore that is offset from GMT or UT1 (not UTC) by twelve hours is bisected by the nautical date line into two 7. Greenwich Mean Time ( GMT) is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London 5° gores that differ from GMT by ±12 hours. A nautical date line is implied but not explicitly drawn on time zone maps. It follows the 180th meridian except where it is interrupted by territorial waters adjacent to land, forming gaps: it is a pole-to-pole dashed line. The 180th meridian or antimeridian is the meridian defined as 180° longitude Territorial waters, or a territorial sea, as defined by the 1982 United Nations Convention on the Law of the Sea, is a belt of coastal waters extending at most

A ship within the territorial waters of any nation would use that nation's standard time, but would revert to nautical standard time upon leaving its territorial waters. Territorial waters, or a territorial sea, as defined by the 1982 United Nations Convention on the Law of the Sea, is a belt of coastal waters extending at most The captain was permitted to change the ship's clocks at a time of the captain’s choice following the ship's entry into another time zone. The captain often chooses midnight.

For airplanes, similar principles apply.

Skewing of zones

Difference between sun time and clock time during daylight saving time: 0h ± 30m 1h ± 30m ahead 2h ± 30m ahead 3h ± 30m ahead
Difference between sun time and clock time during daylight saving time:
0h ± 30m
1h ± 30m ahead
2h ± 30m ahead
3h ± 30m ahead

Ideal time zones, such as nautical time zones, are based on the mean solar time of a particular meridian located in the middle of that zone with boundaries located 7. 5 degrees east and west of the meridian. In practice, zone boundaries are often drawn much farther to the west with often irregular boundaries, and some locations base their time on meridians located far to the east.

For example, even though the Prime Meridian (0°) passes through Spain and France, they use the mean solar time of 15 degrees east (Central European Time) rather than 0 degrees (Greenwich Mean Time). Spain () or the Kingdom of Spain (Reino de España is a country located mostly in southwestern Europe on the Iberian Peninsula. This article is about the country For a topic outline on this subject see List of basic France topics. Central European Time ( CET) is one of the names of the Time zone that is 1 hour ahead of Coordinated Universal Time. Greenwich Mean Time ( GMT) is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London France previously used GMT, but it was switched to CET during the German Occupation and did not switch back after the war.

There is a tendency to draw time zone boundaries far to the west of their meridians. Many of these locations also use daylight saving time which means that solar noon could occur later than 14:00 by the clock.

In a more extreme example, Nome, Alaska is at 165°24′W longitude, which is just west of center of the idealized Samoa Time Zone (165°W). Nome is a city located on the southern Seward Peninsula coast on Norton Sound of the Bering Sea The Samoa Time Zone observes Standard time by subtracting eleven hours from Coordinated Universal Time ( UTC-11) Nevertheless, Nome observes Alaska Time (135°W) with DST so it is slightly more than two hours ahead of the sun in winter and over three in summer. The Alaska Time Zone observes Standard time by subtracting nine hours from Coordinated Universal Time ( UTC-9) [3] Kotzebue, Alaska, also near the same meridian but north of the Arctic Circle, has an annual event on the Ninth of August to celebrate two sunsets the same day, one shortly after midnight and the other shortly before midnight.

Also, China extends as far west as 73°34′E, but all parts of it use UTC+8 (120°E), so solar "noon" can occur as late as 15:00. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National UTC+8 is a band of Timezones separated from the Greenwich Mean Time by 8 hours

Daylight saving time

     DST used      DST no longer used      DST never used
     DST used      DST no longer used      DST never used
Main article: Daylight saving time

Many countries, or even parts of countries, adopt daylight saving time during part of the year. Daylight saving time ( DST Daylight saving time ( DST This typically involves advancing clocks by an hour near the start of spring and adjusting back in autumn. Circadian Locomotor Output Cycles Kaput, or Clock is a gene which encodes proteins regulating Circadian rhythm. The hour (symbol h) is a unit of Time. It is not an SI unit but is accepted for use with the SI Spring is one of the four Temperate Seasons Spring marks the transition from Winter into Summer. Autumn (also known as fall in North American English) is one of the four Temperate Seasons Autumn marks the transition from Summer Some countries also use backward daylight saving over the winter period. Modern DST was first proposed in 1907 and was widespread use in 1916 as a wartime measure aimed at conserving coal. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All Energy conservation is the practice of decreasing the quantity of energy used Despite controversy, many countries have used it since then; details vary by location and change occasionally. Daylight saving time around the world showing usage and a short history by location in alphabetic order

Additional information

Internet and computer systems

UTC is used on the Internet for meetings (i. e. IRC chats, news, shows and so on).

The format is based in the W3C Note "datetime".

On the other hand, most modern computer operating systems include information about time zones, including the capability to automatically change the local time when daylight saving starts and finishes (see the article on daylight saving time for more details on this aspect). An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination Daylight saving time ( DST

NTP

The protocol used the most to synchronize time with multiple sources across the internet is Network Time Protocol (NTP). The Network Time Protocol ( NTP) is a protocol for distributing the Coordinated Universal Time (UTC by means of synchronizing the clocks of computer systems It operates across multiple platforms and there are a wide array of public servers available on the internet to synchronize with. Every server is normally kept updated with an atomic clock belonging to the standards institution of each country. An atomic clock is a type of Clock that uses an Atomic resonance Frequency standard as its timekeeping element Normally a large organization has an internal server to keep time with one of the public NTP servers on the internet, and then this server acts as a proxy and becomes the official timekeeper for all organization machines. NTP is so popular now that virtually all IP-capable devices implement some degree of NTP client software. The Internet Protocol ( IP) is a protocol used for communicating data across a Packet-switched Internetwork using the Internet Protocol

Unix

Main article: Unix time

Most Unix-like systems, including Linux and Mac OS X, keep system time as UTC (Coordinated Universal Time). Unix time, or POSIX time, is a system for describing points in Time, defined as the number of seconds elapsed since Midnight Coordinated Universal A Unix-like (sometimes shortened to *nix) Operating system is one that behaves in a manner similar to a Unix system while not necessarily conforming Linux (commonly pronounced ˈlɪnəks Mac OS X (mæk oʊ ɛs tɛn is a line of computer Operating systems developed marketed and sold by Apple Inc, the latest of which is pre-loaded on all currently Rather than having a single timezone set for the whole computer, timezone offsets can vary for different processes. Standard library routines are used to calculate the local time based on the current timezone, normally supplied to processes through the TZ environment variable. Environment variables are a set of dynamic values that can affect the way running processes will behave on a computer This allows users in multiple timezones to use the same computer, with their respective local times displayed correctly to each user. Timezone information is most commonly stored in a timezone database known as zoneinfo (or sometimes tz or Olson format). The zoneinfo database also called the tz database, is a collaborative compilation of information about the world's Time zones primarily intended for use with computer In fact, many systems, including anything using the GNU C Library, can make use of this database. The GNU C Library, commonly known as glibc, is the C standard library released by the GNU Project.

Microsoft Windows

Windows based computer systems normally keep system time as local time in a particular time zone. Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. A system database of timezone information includes the offset from UTC and rules that indicate the start and end dates for daylight saving in each zone. Application software is able to calculate the time in various zones, but there is no standard way for users from multiple zones to use a single server and have their own local time presented to them other than with Windows 2003 Terminal Server. Windows 2003 Terminal Servers allow remote computers to redirect their time zone settings to the Terminal Server so that users see the correct time for their time zone in their desktop/application sessions. Terminal Services uses the server base time on the Terminal Server and the client time zone information to calculate the time in the session. It shoud be noted that by default, this feature is disabled.

Smalltalk

Each Smalltalk dialect comes with its own built-in classes for dates, times and timestamps, only a few of which implement the DateAndTime and Duration classes as specified by the ANSI Smalltalk Standard. Smalltalk is an object-oriented, dynamically typed, reflective programming language. VisualWorks provides a TimeZone class that supports up to 2 annually-recurring offset transitions, which are assumed to apply to all years (same behavior as Windows time zones. VisualWorks is one of the leading implementations of the Smalltalk programming language and environment ) Squeak provides a Timezone class that does not support any offset transitions. The Squeak Programming language is a Smalltalk implementation derived directly from Smalltalk-80 by a group at Apple Computer that included some of the original Smalltalk-80 Dolphin Smalltalk does not support time zones at all. Dolphin Smalltalk, or "Dolphin" for short, is an implementation of the Smalltalk Programming language by Object Arts, targeted to the

For full support of the Olson Time Zone Database (zoneinfo) in a Smalltalk application (including support for any number of annually-recurring offset transitions, and support for different intra-year offset transition rules in different years) the third-party, open-source, ANSI-Smalltalk-compliant Chronos Date/Time Library is available for use with any of the following Smalltalk dialects: VisualWorks, Squeak or Dolphin. The zoneinfo database also called the tz database, is a collaborative compilation of information about the world's Time zones primarily intended for use with computer The zoneinfo database also called the tz database, is a collaborative compilation of information about the world's Time zones primarily intended for use with computer

Java

While most application software will use the underlying operating system for timezone information, the Java Platform, from version 1. 3. 1, has maintained its own timezone database. This database will need to be updated whenever timezone rules change. Sun provides a Timezone Updater Tool for this purpose.

As an alternative to the timezone information bundled with the Java Platform, programmers may choose to use the Joda-Time library. This library includes its own timezone data based on the frequently-updated tz database.

Python

The standard module datetime stores and operates on the timezone information class tzinfo. The third party pytz module provides access to the full zoneinfo database.

Databases

Some databases allow storage of a datetime type having time zone information. A Computer Database is a structured collection of records or data that is stored in a computer system The SQL standard defines two standard time data types:

TIMESTAMP WITH TIME ZONE
TIMESTAMP WITHOUT TIME ZONE

However the standard has a somewhat naive understanding of time zones. It generally assumes a time zone can be specified by a simple offset from GMT. This causes problems when trying to do arithmetic on dates which span daylight saving time transitions or which span political changes in time zone rules.

Oracle

Oracle Database is configured with a database time zone, and connecting clients are configured with session time zones. Oracle Database uses two data types to store time zone information:

TIMESTAMP WITH TIME ZONE 
Stores date and time information with the offset from UTC
TIMESTAMP WITH LOCAL TIME ZONE 
Stores date and time information with respect to the dbtimezone (which cannot be changed so long as there is a column in the db of this type), automatically adjusting the date and time from the stored time zone to the client's session time zone.

PostgreSQL

PostgreSQL uses the standard SQL data types but tries to impose an interpretation which avoids the problems described above. PostgreSQL is an Object-relational database management system (ORDBMS

TIMESTAMP WITH TIME ZONE 
Stores date and time in UTC and converts to the client's local time zone (which could be different for each client) for display purposes.
TIMESTAMP WITHOUT TIME ZONE 
Stores date and time without any conversion on input or output.

See also

References

  1. ^ Bristol Time
  2. ^ Economics of Time ZonesPDF (1. ISO 8601 is an International standard for date and Time representations issued by the International Organization for Standardization (ISO This is a list of Time zones sorted by Time offsets from Coordinated Universal Time (UTC Daylight saving time ( DST The zoneinfo database also called the tz database, is a collaborative compilation of information about the world's Time zones primarily intended for use with computer Jet lag, also jetlag or jet-lag, is a physiological condition which is a consequence of alterations to Circadian rhythms it is classified 89 MiB)
  3. ^ Doug O'Hara (2007-03-11). A mebibyte (a contraction of me ga bi nary byte) is a unit of Information or Computer storage, abbreviated MiB. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1425 BC - Thutmose III, Pharaoh of Egypt, dies (according to the Low Chronology of the 18th Dynasty Alaska: daylight stealing time. Far North Science. Retrieved on 2007-05-11. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 330 - Byzantium is renamed ''Nova Roma'' during a dedication ceremony but is more popularly referred to as Constantinople

External links

Dictionary

time zone

-noun

  1. A range of longitudes where a common standard time is used.
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