Although not used by most of the world's people, daylight saving time is common in high latitudes. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the      DST used      DST no longer used      DST never used

Daylight saving time (DST; also summer time in British English; see Terminology) is the convention of advancing clocks so that afternoons have more daylight and mornings have less. British English or UK English ( BrE, BE, en-GB) is the broad term used to distinguish the forms of the English language used in the Typically clocks are adjusted forward one hour near the start of spring and are adjusted backward in autumn. Autumn (also known as fall in North American English) is one of the four Temperate Seasons Autumn marks the transition from Summer Modern DST was first proposed in 1907 by William Willett. William Willett ( 10 August 1856 &ndash 4 March 1915) is the inventor of Daylight saving time. 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

The practice is controversial. ^[1] Adding daylight to afternoons benefits retailing, sports, and other activities that exploit sunlight after working hours,^[2] but causes problems for farming, entertainment and other occupations tied to the sun. ^[3][4] Extra afternoon daylight reduces traffic fatalities;^[5] its effect on health and crime is less clear. Although an early goal of DST was to reduce evening usage of incandescent lighting, formerly a primary use of electricity,^[6] modern heating and cooling usage patterns greatly differ and research about how DST currently affects energy use is limited and contradictory. The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general ^[7]

DST's clock shifts can serve as fire safety reminders,^[8] but they complicate timekeeping and can disrupt meetings, travel, billing, recordkeeping, medical devices, and heavy equipment. ^[9] Many computer-based systems can adjust their clocks automatically, but this can be limited and error-prone, particularly when DST rules change. ^[10]

Origin

In this ancient water clock, a series of gears rotated a cylinder to display hour lengths appropriate for each day's date. A water clock or clepsydra ( Greek kleptein to steal; hydro water) is any timekeeper operated by means of a regulated flow of liquid into (inflow

Although not punctual in the modern sense, ancient civilizations adjusted daily schedules to the sun more flexibly than modern DST does, often dividing daylight into twelve equal hours regardless of day length, so that each daylight hour was longer during summer. ^[11] For example, Roman water clocks had different scales for different months of the year: at Rome's latitude the third hour from sunrise, hora tertia, started by modern standards at 09:02 solar time and lasted 44 minutes at the winter solstice, but at the summer solstice it started at 06:58 and lasted 75 minutes. A water clock or clepsydra ( Greek kleptein to steal; hydro water) is any timekeeper operated by means of a regulated flow of liquid into (inflow Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the Terce, or Third Hour, is a fixed time of prayer of the Divine Office of almost all the Christian liturgies Solar times are measures of the apparent position of the Sun on the Celestial sphere. Solstices occur twice a year when the tilt of the Earth's axis is most oriented toward or away from the Sun, causing the Sun to reach its northernmost and southernmost extremes ^[12] After ancient times, equal-length civil hours eventually supplanted unequal, so civil time no longer varies by season. In modern usage civil time refers to statutory time scales designated by civilian authorities or to local time indicated by clocks Unequal hours are still used in a few traditional settings, such as some Mount Athos monasteries. Mount Athos (Όρος Άθως is a mountain on the Peninsula of the same name in Macedonia, of northern Greece, called in Greek Άγιον ^[13]

Benjamin Franklin suggested firing cannons at sunrise to waken Parisians. Benjamin Franklin ( April 17 1790 was one of the Founding Fathers of the United States of America.

During his time as an American envoy to France, Benjamin Franklin, author of the proverb, "Early to bed, and early to rise, makes a man healthy, wealthy and wise", anonymously published a letter suggesting that Parisians economize on candles by rising earlier to use morning sunlight. Benjamin Franklin ( April 17 1790 was one of the Founding Fathers of the United States of America. Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city A candle is a Light source and sometimes a Heat source consisting of a solid block of Fuel and an embedded wick. ^[14] This 1784 satire proposed taxing shutters, rationing candles, and waking the public by ringing church bells and firing cannons at sunrise. Satire is often strictly defined as a literary genre or form; although in practice it is also found in the graphic and Performing arts In satire human A window shutter is a solid and stable Window covering usually consisting of a frame of vertical stiles and horizontal rails (top center and bottom ^[15] Franklin did not propose DST; like ancient Rome, 18th-century Europe did not keep accurate schedules. However, this soon changed as rail and communication networks came to require a standardization of time unknown in Franklin's day. "Railroad" and "Railway" both redirect here For other uses see Railroad (disambiguation. ^[16]

William Willett conceived DST and advocated it tirelessly. William Willett ( 10 August 1856 &ndash 4 March 1915) is the inventor of Daylight saving time. ^[17]

The prominent English builder and outdoorsman William Willett conceived DST in 1905 during one of his pre-breakfast horseback rides, when he observed with dismay how many Londoners slept through the best part of a summer day. William Willett ( 10 August 1856 &ndash 4 March 1915) is the inventor of Daylight saving time. London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. ^[18] An avid golfer, he also disliked cutting short his round at dusk. His solution was to advance the clock during the summer months, a proposal he published two years later. ^[19] He lobbied unsuccessfully for the proposal until his death in 1915; see Politics for more details.

Germany, its World War I allies, and their occupied zones were the first European nations to use Willett's invention, starting April 30, 1916. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All Events 313 - Roman emperor Licinius unifies the entire Eastern Roman Empire under his rule Year 1916 ( MCMXVI) was a Leap year starting on Saturday (link will display the full calendar of the Gregorian calendar (or a Leap year Britain, most of its allies, and many European neutrals soon followed suit; Russia and a few other countries waited until the next year; and the United States adopted it in 1918. Since then, the world has seen many enactments, adjustments, and repeals. ^[20]

Benefits and drawbacks

Willett's 1907 proposal argued that DST increases opportunities for outdoor leisure activities during afternoon sunlight hours. Leisure or free time, is a period of Time spent out of work and essential domestic Activity. Obviously it does not change the length of the day; the longer days nearer the summer solstice in high latitudes merely offer more room to shift apparent daylight from morning to evening so that early morning daylight is not wasted. ^[19] DST is commonly not observed during most of winter, because its mornings are darker: workers may have no sunlit leisure time, and children may need to leave for school in the dark. ^[21]

General agreement about the day's layout confers so many advantages that a standard DST schedule usually outranks ad hoc efforts to get up earlier, even for people who personally dislike the DST schedule. Ad hoc is a Latin phrase which means "for this [ Purpose ]" ^[22] The advantages of coordination are so great that many people ignore whether DST is in effect by altering their nominal work schedules to coordinate with daylight, television broadcasts, or remote colleagues. ^[23]

Energy use

Delaying the nominal time of sunset and sunrise reduces the use of artificial light in the evening and increases it in the morning. As Franklin's 1784 satire pointed out, lighting costs are reduced if the evening reduction outweighs the morning increase, as in high-latitude summer when most people wake up well after sunrise. An early goal of DST was to reduce evening usage of incandescent lighting, formerly a primary use of electricity. ^[6] Although energy conservation remains an important goal,^[24] energy usage patterns have greatly changed since then, and recent research is limited and reports contradictory results. ^[7] Electricity use is greatly affected by geography, climate, and economics, making it hard to generalize from single studies. ^[7]

• The U.S. Dept. of Transportation (DOT) concluded in 1975 that DST might reduce the country's electricity usage by 1% during March and April,^[7] but the National Bureau of Standards (NBS) reviewed the DOT study in 1976 and found no significant savings. The United States Department of Transportation ( DOT) is a federal Cabinet department of the United States government concerned with Transportation ^[21]
• In 2000 when parts of Australia began DST in late winter, overall electricity consumption did not decrease, but the morning peak load and prices increased. Standard time was introduced into Australia in the 1890s when all colonies adopted standard times ^[25]
• In Western Australia during summer 2006–07, DST increased electricity consumption during hotter days and decreased it during cooler days, with consumption rising 0. Western Australia is a state occupying the entire western third of the Australian continent. 6% overall. ^[26]
• Although a 2007 study estimated that introducing DST to Japan would reduce household lighting energy consumption,^[27] a 2007 simulation estimated that DST would increase overall energy use in Osaka residences by 0. is a city in Japan, located at the mouth of the Yodo River on Osaka Bay, in the Kansai region of the main island of Honshū 13%, with a 0. 02% decrease due to less lighting more than outweighed by a 0. 15% increase due to extra cooling; neither study examined non-residential energy use. ^[28] DST's effect on lighting energy use is noticeable mainly in residences. ^[7]
• A 2007 study found that the earlier start to DST that year had little or no effect on electricity consumption in California. ^[29]
• A 2007 study estimated that winter daylight saving would prevent a 2% increase in average daily electricity consumption in Great Britain. See also Kingdom of Great Britain Great Britain (Breatainn Mhòr Prydain Fawr Breten Veur Graet Breetain is the larger of the two main islands ^[30]
• A 2008 study examined billing data in Indiana before and after it adopted DST in 2006, and concluded that DST increased residential electricity consumption by 1% to 4%, primarily due to extra afternoon cooling. ^[31]

Several studies have suggested that DST increases motor fuel consumption. ^[7] U. S. gasoline demand grew an extra 1% during the newly introduced DST in March 2007. ^[32]

Economic effects

Retailers, sporting goods makers, and other businesses benefit from extra afternoon sunlight, as it induces customers to shop and to participate in outdoor afternoon sports. ^[33] For example, in 1984 Fortune magazine estimated that a seven-week extension of DST would yield an additional $30 million for 7-Eleven stores, and the National Golf Foundation estimated the extension would increase golf industry revenues $200 million to $300 million. 7-Eleven is a worldwide chain of Convenience stores It is since March 2007 the largest chain store in any category beating McDonald's by 1000 stores The National Golf Foundation provides Golf -business research and consulting services ^[34] A 1999 study estimated that DST increases the revenue of the European Union's leisure sector by about 3%. In business revenue or revenues is Income that a company receives from its normal business activities usually from the sale of goods and services The European Union ( EU) is a political and economic union of twenty-seven member states, located primarily in ^[7] Conversely, DST can adversely affect farmers and others whose hours are set by the sun. ^[3] For example, grain harvesting is best done after dew evaporates, so when field hands arrive and leave earlier in summer their labor is less valuable. Formation Water will condense into droplets depending on the temperature ^[35] DST also hurts prime-time broadcast ratings^[4] and drive-in and other theaters. A drive-in theater is a form of cinema structure consisting of a large outdoor screen a projection booth a Concession stand and a large parking area for automobiles Theatre (or theater, see spelling differences) is the branch of the Performing arts defined by Bernard Beckerman as what "occurs when one ^[36]

Clock shifts correlate with decreased economic efficiency. In 2000 the daylight-saving effect implied an estimated one-day loss of $31 billion on U. S. stock exchanges. ^[37] Clock shifts and DST rule changes have a direct economic cost, entailing extra work to support remote meetings, computer applications and the like. For example, a 2007 North American rule change cost an estimated $500 million to $1 billion. ^[38]

Public safety

In 1975 the U. S. DOT conservatively identified a 0. 7% reduction in traffic fatalities during DST, and estimated the real reduction to be 1. 5% to 2%,^[39] but the 1976 NBS review of the DOT study found no differences in traffic fatalities. ^[21] In 1995 the Insurance Institute for Highway Safety estimated a reduction of 1. The Insurance Institute for Highway Safety is a US Non-profit organization funded by auto insurers 2%, including a 5% reduction in crashes fatal to pedestrians. ^[5] Others have found similar reductions. ^[40] Single/Double Summer Time (SDST), a variant where clocks are one hour ahead of the sun in winter and two in summer, has been projected to reduce traffic fatalities by 3% to 4% in the UK, compared to ordinary DST. ^[41] It is not clear whether sleep disruption contributes to fatal accidents immediately after the spring clock shifts. Sleep is a Natural state of bodily rest observed throughout the animal kingdom ^[42] A correlation between clock shifts and accidents has been observed in North America but not in Finland or Sweden. Finland, officially the Republic of Finland ( is a Nordic country situated in the Fennoscandian region of northern Europe. "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. If this effect exists, it is far smaller than the overall reduction in fatalities. ^[43]

In the 1970s the U. S. Law Enforcement Assistance Administration (LEAA) found a reduction of 10% to 13% in Washington, D.C.'s violent crime rate during DST. The Law Enforcement Assistance Administration ( LEAA) was a U Washington DC ( formally the District of Columbia and commonly referred to as Washington, the District, or simply D However, the LEAA did not filter out other factors, and it examined only two cities and found crime reductions only in one and only in some crime categories; the DOT decided it was "impossible to conclude with any confidence that comparable benefits would be found nationwide". ^[44] Outdoor lighting has a marginal and sometimes even contradictory influence on crime and fear of crime. ^[45]

In several countries, fire safety officials encourage citizens to use the two annual clock shifts as reminders to replace batteries in smoke and carbon monoxide detectors, particularly in autumn, just before the heating and candle season causes an increase in home fires. Fire safety refers to precautions that are taken to prevent or reduce the likelihood of a Fire that may result in death injury or property damage alert those in a structure A smoke detector is a device that detects Smoke and issues an Alarm. A carbon monoxide detector or CO detector is a device that detects the presence of the Toxic gas Carbon monoxide (CO a colorless and odorless compound HVAC (pronounced either "H-V-A-C" or occasionally " H-vak " is an Initialism or Acronym that stands for " Heating Similar twice-yearly tasks include reviewing and practicing fire escape and family disaster plans, inspecting vehicle lights, checking storage areas for hazardous materials, and reprogramming thermostats. A thermostat is a device for regulating the Temperature of a System so that the system's temperature is maintained near a desired setpoint ^[46][47][8] This is not an essential function of DST, as locations without DST can instead use the first days of spring and autumn as reminders. ^[48]

Health

Clock shifts affect apparent sunrise and sunset times at Greenwich in 2007. Greenwich ( ˈɡrɛnɪtʃ GREN-itch /ˈɡrɛnɪdʒ/ GREN-idge or /ˈɡrɪnɪdʒ/ GRIN-idge is a district in south-east London, ^[49]

DST has mixed effects on health. In societies with fixed work schedules it provides more afternoon sunlight for outdoor exercise. ^[50] It alters sunlight exposure; whether this is beneficial depends on one's location and daily schedule, as sunlight triggers vitamin D synthesis in the skin, but overexposure can lead to skin cancer. Skin cancer is a Malignant growth on the Skin which can have many causes ^[51] Sunlight strongly influences seasonal affective disorder. Seasonal affective disorder ( SAD) also known as winter depression, is a Mood disorder in which people who have normal mental health throughout most of the year experience DST may help in depression by causing individuals to rise earlier,^[52] but some argue the reverse. In the fields of Psychology and Psychiatry, the terms depression or depressed refer to both expected and pathologically chronic or severe ^[53] The Retinitis Pigmentosa Foundation Fighting Blindness, chaired by blind sports magnate Gordon Gund, successfully lobbied in 1985 and 2005 for U. Retinitis pigmentosa ( RP) is a group of genetic Eye conditions Gordon Gund (born October 15, 1939) is the former principal owner of the NBA 's Cleveland Cavaliers, a co-owner of the San Jose Sharks S. DST extensions,^[2][54] but DST can hurt night blindness sufferers. Nyctalopia (Greek for " night blindness " is a condition making it difficult or impossible to see in relatively low light ^[55]

Clock shifts disrupt sleep and reduce its efficiency. ^[56] Effects on seasonal adaptation of the circadian rhythm can be severe and last for weeks. ^[57] A 2008 study found that although male suicide rates rise in the weeks after the spring transition, the relationship weakened greatly after adjusting for season. ^[58] The government of Kazakhstan cited health complications due to clock shifts as a reason for abolishing DST in 2005. Kazakhstan, also Kazakstan ( Қазақстан, Qazaqstan, qɑzɑqˈstɑn Казахстан, Kazakhstán,) officially the ^[59]

Complexity

DST's clock shifts have the obvious disadvantage of complexity. People must remember to change their clocks; this consumes time, particularly for mechanical clocks that cannot be moved backward safely. ^[60] As more devices contain clocks, more time is spent changing them. ^[61] People who work across time zone boundaries need to keep track of multiple DST rules, as not all locations observe DST or observe it the same way. The length of the day becomes variable. Disruption to meetings, travel, broadcasts, billing systems, and records management is common, and can be expensive. ^[62] During an autumn transition from 02:00 to 01:00, a clock reads times from 01:00 to 02:00 twice, possibly leading to confusion. ^[63]

Some computer-based systems require downtime or restarting when clocks shift; ignoring this requirement damaged a German steel facility in 1993. ^[9] Medical devices may generate adverse events that could harm patients, without being obvious to clinicians responsible for care. ^[64] These problems are compounded when the DST rules themselves change, as in the Year 2007 problem. The Year 2007 problem also known as Y2K7 (or DST07 is an issue caused by a US-mandated change to Daylight saving time, which has repercussions in the computer Software developers must test and perhaps modify many programs, and users must install updates and restart applications. ^[10]

Some clock-shift problems could be avoided by adjusting clocks continuously^[65] or at least more gradually—for example, Willett originally suggested weekly 20-minute transitions—but this would add complexity and has never been implemented.

The William Willett Memorial Sundial is always on DST. William Willett ( 10 August 1856 &ndash 4 March 1915) is the inventor of Daylight saving time.

DST inherits and can magnify the disadvantages of standard time. For example, when reading a sundial, one must compensate for it along with time zone and natural discrepancies. A sundial is a device that measures time by the position of the Sun. ^[66] Also, sun-exposure rules like "avoid the sun within two hours of noon" become less accurate when DST is in effect. ^[67]

Politics

Daylight saving has caused controversy since it began. ^[1] Winston Churchill argued that it enlarges "the opportunities for the pursuit of health and happiness among the millions of people who live in this country". Sir Winston Leonard Spencer-Churchill, KG, OM, CH, TD, FRS, PC, PC (Can ( 30 November 1874 ^[68] Robertson Davies, however, detected "the bony, blue-fingered hand of Puritanism, eager to push people into bed earlier, and get them up earlier, to make them healthy, wealthy and wise in spite of themselves",^[69] and wags have dubbed it "Daylight Slaving Time". William Robertson Davies, CC, FRSC, FRSL (born August 28, 1913, at Thamesville, Ontario, and died December ^[70] Historically, retailing, sports and tourism interests have favored daylight saving, while agricultural and evening entertainment interests have opposed it, and its initial adoption has been prompted by energy crisis and war. An energy crisis is any great bottleneck (or price Rise) in the supply of energy resources to an economy. ^[71]

The fate of Willett's 1907 proposal illustrates several political issues involved. The proposal attracted many supporters, including Balfour, Churchill, Lloyd George, MacDonald, Edward VII (who used half-hour DST at Sandringham), the managing director of Harrods, and the manager of the National Bank. Arthur James Balfour 1st Earl of Balfour, KG, OM, PC (25 July 1848 - 19 March 1930 was a British Conservative politician and David Lloyd George 1st Earl Lloyd George of Dwyfor OM, PC (17 January 1863 &ndash 26 March 1945 was a British Statesman and the only James Ramsay MacDonald ( 12 October 1866 &ndash 9 November 1937) was a British politician and twice Prime Minister of the United Sandringham time is the name given to the idiosyncratic alterations that King Edward VII made to the timekeeping at the royal estate of Sandringham. Harrods is a Department store located on Brompton Road in Knightsbridge, London, England. However, the opposition was stronger: it included Prime Minister Asquith, Christie (the Astronomer Royal), George Darwin, Napier Shaw (director of the Meteorological Office), many agricultural organizations, and theater owners. Herbert Henry Asquith 1st Earl of Oxford and Asquith, KG, PC ( 12 September 1852 &ndash 15 February 1928) served Sir William Henry Mahoney Christie FRS ( 1 October 1845 &ndash 22 January 1922) was a British Astronomer. Astronomer Royal is a senior post in the Royal Household of the Sovereign of the United Kingdom. Sir George Howard Darwin, FRS ( July 9 1845 &ndash Cambridge, December 7 1912) was an English Sir William Napier Shaw FRS, ( March 4, 1854 - March 23, 1945) was a British Meteorologist. For the UKMET model see Tropical cyclone forecast model. The Met Office (originally an abbreviation for Meteorological Office, After many hearings the proposal was narrowly defeated in a Parliament committee vote in 1909. The Parliament of the United Kingdom of Great Britain and Northern Ireland is the supreme legislative body in the United Kingdom and British overseas territories Willett's allies introduced similar bills every year from 1911 through 1914, to no avail. ^[72] The U. S. was even more skeptical: Andrew Peters introduced a DST bill to the U.S. House in May 1909, but it soon died in committee. Andrew James Peters was a member of the United States House of Representatives, representing Massachusetts's 11th congressional district from 1907 to 1914 and The United States House of Representatives is one of the two chambers of the United States Congress; the other is the Senate. ^[73]

Retailers generally favor DST. United Cigar Stores hailed a 1918 DST bill. United Cigar Stores was the largest chain of Cigar stores in the United States

World War I changed the political equation, as DST was promoted as a way to alleviate hardships from wartime coal shortages and air raid blackouts. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All After Germany led the way, the United Kingdom first used DST on May 21, 1916. Events 878 - Syracuse Italy is captured by the Muslim sultan of Sicily. Year 1916 ( MCMXVI) was a Leap year starting on Saturday (link will display the full calendar of the Gregorian calendar (or a Leap year ^[74] U. S. retailing and manufacturing interests led by Pittsburgh industrialist Robert Garland soon began lobbying for DST, but were opposed by railroads. The U. S. 's 1917 entry to the war overcame objections, and DST was established in 1918. ^[75]

War's end swung the pendulum back. Farmers continued to dislike DST, and many countries repealed it after the war. Britain was an exception: it retained DST nationwide but over the years adjusted transition dates for several reasons, including special rules during the 1920s and 1930s to avoid clock shifts on Easter mornings. ^[76] The U. S. was more typical: Congress repealed DST after 1919. President Woodrow Wilson, like Willett an avid golfer, vetoed the repeal twice but his second veto was overridden,^[77] and only a few U. Thomas Woodrow Wilson (December 28 1856—February 3 1924 was the twenty-eighth President of the United States. S. cities retained DST locally thereafter. ^[78] Wilson's successor Warren G. Harding opposed DST as a "deception". Warren Gamaliel Harding (November 2 1865 August 2 1923 was the twenty-ninth President of the United States, serving from 1921 until his death from a heart attack aged Reasoning that people should instead get up and go to work earlier in the summer, he ordered District of Columbia federal employees to start work at 08:00 rather than 09:00 during summer 1922. Washington DC ( formally the District of Columbia and commonly referred to as Washington, the District, or simply D Many businesses followed suit though many others did not; the experiment was not repeated. ^[79]

Since Willett's day the world has seen many enactments, adjustments, and repeals of DST, with similar politics involved. ^[80] The history of time in the United States includes DST during both world wars, but no standardization of peacetime DST until 1966. ^[81] In the mid-1980s, Clorox (parent of Kingsford Charcoal) and 7-Eleven provided the primary funding for the Daylight Saving Time Coalition behind the 1987 extension to U. The Clorox Company ( is a Manufacturer of various food and Chemical products based in Oakland California, which is best known for its Bleach Kingsford is a brand of Charcoal used for Grilling, along with related products S. DST, and both Idaho senators voted for it on the basis of fast-food restaurants selling more French fries made from Idaho potatoes;^[2] in 2005, the Sporting Goods Manufacturers Association and the National Association of Convenience Stores successfully lobbied for the 2007 extension to U. The State of Idaho ( is a state in the Pacific Northwest region of the United States of America. The United States Senate is the Upper house of the bicameral United States Congress, the Lower house being the House of Representatives The Sporting Goods Manufacturers Association (SGMA is a Trade association that represents Sporting goods manufacturers retailers and marketers The National Association of Convenience Stores (NACS is a Trade association that represents convenience and petroleum retailers S. DST. ^[54] In early 2007, Western Australia continued to debate a trial use of DST and several politicians changed positions after public sentiment swung against it. Western Australia is a state occupying the entire western third of the Australian continent. ^[82] In the UK the sport and leisure industry supports a proposal to observe SDST's additional hour year-round. ^[83]

Observance practices

Main article: Daylight saving time around the world

Clocks advance when DST starts. Daylight saving time around the world showing usage and a short history by location in alphabetic order

In a typical case where a one-hour shift occurs at 02:00 local time, in spring the clock jumps forward from 02:00 standard time to 03:00 DST and the day has 23 hours, whereas in autumn the clock jumps backward from 02:00 DST to 01:00 standard time, repeating that hour, and the day has 25 hours. 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 A digital display of local time does not read 02:00 exactly, but instead jumps from 01:59:59. 9 either forward to 03:00:00. 0 or backward to 01:00:00. 0. In this example, a location observing UTC+10 during standard time is at UTC+11 during DST; conversely, a location at UTC−10 during standard time is at UTC−9 during DST. The UTC+10 Time zone covers the following locations Australia (AEST&mdash Australian Eastern Standard Time) Australian UTC+11 is the Time zone for the following locations As standard (non-DST time Federated States of Micronesia The UTC−10 Time offset is used in Cook Islands French Polynesia Society Archipelago including The UTC−9 time zone is used in French Polynesia Gambier Islands United States (AKST— Alaska Standard

Clock shifts are usually scheduled near a weekend midnight to lessen disruption to weekday schedules. A one-hour shift is customary, but Australia's Lord Howe Island uses a half-hour shift. Lord Howe Island (ˈhaʊ is a small island in the Pacific Ocean east of the Australian mainland ^[84] Twenty-minute and two-hour shifts have been used in the past.

Coordination strategies differ when adjacent time zones shift clocks. The European Union shifts all at once, at 01:00 UTC; for example, Eastern European Time is always one hour ahead of Central European Time. The European Union ( EU) is a political and economic union of twenty-seven member states, located primarily in Eastern European Time ( EET) is one of the names of UTC+2 Time zone, 2 hours ahead of Coordinated Universal Time. Central European Time ( CET) is one of the names of the Time zone that is 1 hour ahead of Coordinated Universal Time. ^[76] Most of North America shifts at 02:00 local time, so its zones do not shift at the same time; for example, Mountain Time can be temporarily either zero or two hours ahead of Pacific Time. The Mountain Time Zone of North America keeps time by subtracting seven hours from Coordinated Universal Time ( UTC-7) during the shortest days of autumn The Pacific Time Zone observes Standard time by subtracting eight hours from Coordinated Universal Time ( UTC-8) Australian districts go even further and do not always agree on start and end dates; for example, to start DST in 2006 Tasmania shifted clocks forward on 1 October, Western Australia on 3 December, and the remaining DST-observing areas on 29 October. Standard time was introduced into Australia in the 1890s when all colonies adopted standard times Tasmania is an Australian island and state of the same name It is located south of the eastern side of the Continent, being separated from it by Bass Events 331 BC - Alexander the Great defeats Darius III of Persia in the Battle of Gaugamela. Western Australia is a state occupying the entire western third of the Australian continent. Events 1800 - War of the Second Coalition: Battle of Hohenlinden, French Events 437 - Valentinian III, Western Roman Emperor, marries Licinia Eudoxia, daughter of his cousin Theodosius II ^[85]

Start and end dates vary with location and year. Since 1996 European Summer Time has been observed from the last Sunday in March to the last Sunday in October; previously the rules were not uniform across the European Union. European Summer Time is the arrangement in Europe by which clocks are advanced by one hour in Spring to make the most of seasonal daylight ^[76] Starting in 2007, most of the United States and Canada observe DST from the second Sunday in March to the first Sunday in November, almost two-thirds of the year. ^[86] The 2007 U. S. change was part of the Energy Policy Act of 2005; previously, from 1987 through 2006, the start and end dates were the first Sunday in April and the last Sunday in October, and Congress retains the right to go back to the previous dates once an energy-consumption study is done. The Energy Policy Act of 2005 ( is a statute that was passed by the United States Congress on July 29 2005 and signed into law by President George W The United States Congress is the bicameral Legislature of the federal government of the United States of America, consisting of two houses ^[87]

In 2008 central Brazil will be one, two, or three hours ahead of eastern U. S. , depending on the date. ^[88]

Beginning and ending dates are the reverse in the southern hemisphere. Southern Hemisphere is the half of a Planet that is South of the Equator —the word hemisphere literally means 'half ball' For example, mainland Chile observes DST from the second Saturday in October to the second Saturday in March, with transitions at 24:00 local time. Chile uses 4 different UTC offsets Except for Easter Island, it uses UTC-4 and in summer as Daylight saving time UTC-3 ^[89] The time difference between the United Kingdom and mainland Chile may therefore be three, four, or five hours, depending on the time of year.

Time zones often lie west of their idealized boundaries, resulting in year-round DST.

Western China, Iceland, and other areas skew time zones westward, in effect observing DST year-round without complications from clock shifts. The Iceland, officially the Republic of Iceland ( ( Ísland or Lýðveldið Ísland ( For example, Saskatoon, Saskatchewan, is at 106° 39′ W longitude, slightly west of center of the idealized Mountain Time Zone (105° W), but the time in Saskatchewan is Central Standard Time (90° W) year-round, so Saskatoon is always about 67 minutes ahead of mean solar time. Saskatoon is a city located in central Saskatchewan, Canada, on the South Saskatchewan River, with a The Province of Saskatchewan observes Central Standard Time but since it is geographically located in the Mountain Time Zone is effectively on daylight saving time year round The Central Time Zone observes Standard time by subtracting six hours from UTC during standard time ( UTC−6) and five hours during Daylight saving Solar times are measures of the apparent position of the Sun on the Celestial sphere. ^[90] Conversely, northeast India and a few other areas skew time zones eastward, in effect observing negative DST. India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country ^[24] The United Kingdom and Ireland experimented with year-round DST from 1968 to 1971 but abandoned it because of its unpopularity, particularly in northern regions. Ireland ( Irish: Éire, ˈeːrʲə is a country in north-western Europe. ^[91]

Western France, Spain, and other areas skew time zones and shift clocks, in effect observing DST in winter with an extra hour in summer. This article is about the country For a topic outline on this subject see List of basic France topics. Spain () or the Kingdom of Spain (Reino de España is a country located mostly in southwestern Europe on the Iberian Peninsula. For example, Nome, Alaska, is at 165° 24′ W longitude, which is just west of center of the idealized Samoa Time Zone (165° W), but Nome observes Alaska Time (135° W) with DST, so it is slightly more than two hours ahead of the sun in winter and three in summer. 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) The Alaska Time Zone observes Standard time by subtracting nine hours from Coordinated Universal Time ( UTC-9) ^[92]

DST is generally not observed near the equator, where sunrise times do not vary enough to justify it. The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the Some countries observe it only in some regions; for example, southern Brazil observes it while equatorial Brazil does not. |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld ^[93] Only a minority of the world's population uses DST because Asia and Africa generally do not observe it.

Terminology

In the normative form, daylight saving time uses the present participle saving as an adjective, as in labor saving device; the first two words are sometimes hyphenated, as in daylight-saving time. In Linguistics, a participle (from Latin participium, a Calque of Greek μετοχη "partaking" is a derivative of a non-finite Daylight savings time, daylight savings, and daylight time are common variants, the savings by analogy to savings account. Savings accounts are accounts maintained by retail Financial institutions that pay Interest but can not be used directly as Money (by for example ^[94] Willett's original proposal used the term daylight saving, but by 1911 the term summer time replaced daylight saving time in draft legislation in Britain. ^[95]

Time zone names typically change when DST is observed. American English replaces standard with daylight: for example, Pacific Standard Time (PST) becomes Pacific Daylight Time (PDT). Phonology North American English regional phonology In many ways compared to English English, North American English is conservative in its Phonology. The Pacific Time Zone observes Standard time by subtracting eight hours from Coordinated Universal Time ( UTC-8) British English uses summer: for example, Greenwich Mean Time (GMT) becomes British Summer Time (BST). British English or UK English ( BrE, BE, en-GB) is the broad term used to distinguish the forms of the English language used in the Greenwich Mean Time ( GMT) is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London Western European Summer Time ( WEST) is a summer Daylight saving time scheme 1 hour ahead of Coordinated Universal Time. Abbreviations do not always change: for example, many (though not all) Australians say that Eastern Standard Time (EST) becomes Eastern Summer Time (also EST). Standard time was introduced into Australia in the 1890s when all colonies adopted standard times

The American English mnemonic "spring forward, fall back" (also "spring ahead …", "spring up …", and "… fall behind") helps people remember which direction to shift clocks. A mnemonic device (nəˈmɒnɪk is a Memory aid Commonly met mnemonics are often verbal something such as a very short poem or a special word used to help a person remember 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 Much of North America now advances clocks before the vernal equinox, so the mnemonic disagrees with the astronomical definition of spring, but a proposed substitute "March forward …"^[96] works only in the northern hemisphere, and is less robust against future rule changes. An equinox is the event of the Sun passing over the Earth's equator in its annual cycle Events in March American Red Cross Month Fire Prevention month ( The Philippines) Women's History Month ( United Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball'

Computing

A 2001 public service announcement reminded people to adjust clocks manually.

Many computer-based systems can shift their clocks automatically when DST starts and finishes, based on their time zone settings. Two implementations in wide use today are zoneinfo and Microsoft Windows. Some applications standardize on UTC to avoid problems with clock shifts and time zone differences. ^[97]

Zoneinfo

The zoneinfo database maps a name to the named location's historical and predicted clock shifts. 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 This database is used by many computer software systems, including most Unix-like operating systems, Java, and Oracle;^[98] HP's "tztab" database is similar but incompatible. 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 Java refers to a number of Computer software products and specifications from Sun Microsystems that together provide a system for developing Application software Oracle Database (commonly referred to as Oracle RDBMS or simply Oracle) is a Relational database management system (RDBMS produced and marketed by ^[99] When temporal authorities change DST rules, zoneinfo updates are installed as part of ordinary system maintenance. In Unix-like systems the TZ environment variable specifies the location name, as in TZ='America/New_York'. Environment variables are a set of dynamic values that can affect the way running processes will behave on a computer This is a list of Time zones as provided by the Zoneinfo (or tz') database

Older or stripped-down systems may support only the TZ values required by POSIX, which specify at most one start and end rule explicitly in the value. POSIX (ˈpɒzɪks or "Portable Operating System Interface" is the collective name of a family of related standards specified by the IEEE to define For example, TZ='EST5EDT,M3. 2. 0/02:00,M11. 1. 0/02:00' specifies time for eastern North America starting in 2007. TZ must be changed whenever DST rules change, and the new TZ value applies to all years, mishandling some older time stamps. ^[100]

Microsoft Windows

As with zoneinfo, a user of Microsoft Windows configures DST by specifying the name of a location, and the operating system then consults a table of rule sets that must be updated when DST rules change. Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. Procedures for specifying the name and updating the table vary with release. Updates are not issued for older versions of Microsoft Windows. ^[101] Windows Vista supports at most two start and end rules per time zone setting. Windows Vista (ˈvɪstə is a line of Operating systems developed by Microsoft for use on Personal computers including home and business desktops In a Canadian location observing DST, a single Vista setting supports both 1987–2006 and post-2006 time stamps, but mishandles some older time stamps. Older Microsoft Windows systems usually store only a single start and end rule for each zone, so that the same Canadian setting reliably supports only post-2006 time stamps. ^[102]

These limitations have caused problems. For example, before 2005, DST in Israel varied each year and was skipped some years. For a topic outline on this subject see List of basic Israel topics. Windows 95 used rules correct for 1995 only, causing problems in later years. Windows 95 is a consumer-oriented Graphical user interface -based Operating system. In Windows 98 Microsoft gave up and marked Israel as not having DST, forcing Israeli users to shift their computer clocks manually twice a year. Windows 98 ( codenamed Memphis) is a graphical Operating system released on 25 June 1998 by Microsoft and the successor to Windows 95 The 2005 Israeli Daylight Saving Law established predictable rules but Windows zone files cannot represent the rules' dates in a year-independent way. The Israeli Daylight Saving Law ( ħoq qvi'at ha-zman) was approved by the Knesset in 1992, replacing the British mandate time act inherited Partial workarounds, which mishandle older time stamps, include manually switching zone files every year^[103] and a Microsoft tool that switches zones automatically. ^[104]

References

Franklin's 1784 letter about daylight had neither title nor byline. Benjamin Franklin ( April 17 1790 was one of the Founding Fathers of the United States of America. The byline on a Newspaper or Magazine article gives the name and often the position of the writer of the article ^[15]

William Willett's pamphlet promoting DST went through nineteen editions. William Willett ( 10 August 1856 &ndash 4 March 1915) is the inventor of Daylight saving time. ^[19]

Further reading

• Michael Downing (2005). Spring Forward: The Annual Madness of Daylight Saving Time. Shoemaker & Hoard. ISBN 1-59376-053-1.  
• David Prerau (2005). Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time. Thunder’s Mouth Press. ISBN 1-56025-655-9.   The British version, focusing on the UK, is Saving the Daylight: Why We Put the Clocks Forward. Granta Books. ISBN 1-86207-796-7.  

External links

• Daylight Saving Time - general history and anecdotes
• Saving Time, Saving Energy - North American viewpoint
• Summer Time - European viewpoint
• Sources for time zone and daylight saving time data - technical resources