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Date Posted: 06:10:38 02/10/16 Wed
Author: robin hasan
Subject: Daylight saving time

Daylight saving time (DST) or summer time is the practice of advancing clocks during summer months by one hour so that in the evening daylight is experienced an hour longer, while sacrificing normal sunrise times. Typically, regions with summer time adjust clocks forward one hour close to the start of spring and adjust them backward in the autumn to standard time.[1]

New Zealander George Hudson proposed the modern idea of daylight saving in 1895.[2] Germany and Austria-Hungary organized the first nationwide implementation, starting on 30 April 1916. Many countries have used it at various times since then, particularly since the energy crisis of the 1970s.

The practice has received both advocacy and criticism.[1] Putting clocks forward benefits retailing, sports, and other activities that exploit sunlight after working hours,[3] but can cause problems for evening entertainment and for other activities tied to sunlight, such as farming.[4][5] Although some early proponents of DST aimed to reduce evening use of incandescent lighting, which used to be a primary use of electricity,[6] modern heating and cooling usage patterns differ greatly and research about how DST affects energy use is limited or contradictory.[7]

DST clock shifts sometimes complicate timekeeping and can disrupt travel, billing, record keeping, medical devices, heavy equipment,[8] and sleep patterns.[9] Computer software can often adjust clocks automatically, but policy changes by various jurisdictions of the dates and timings of DST may be confusing


Industrialized societies generally follow a clock-based schedule for daily activities that do not change throughout the course of the year. The time of day that individuals begin and end work or school, and the coordination of mass transit, for example, usually remain constant year-round. In contrast, an agrarian society's daily routines for work and personal conduct are more likely governed by the length of daylight hours[11][12] and by solar time, which change seasonally because of the Earth's axial tilt. North and south of the tropics daylight lasts longer in summer and shorter in winter, the effect becoming greater as one moves away from the tropics.

By synchronously resetting all clocks in a region to one hour ahead of Standard Time (one hour "fast"), individuals who follow such a year-round schedule will wake an hour earlier than they would have otherwise; they will begin and complete daily work routines an hour earlier, and they will have available to them an extra hour of daylight after their workday activities.[13][14] However, they will have one less hour of daylight at the start of each day, making the policy less practical during winter.[15][16]

While the times of sunrise and sunset change at roughly equal rates as the seasons change, proponents of Daylight Saving Time argue that most people prefer a greater increase in daylight hours after the typical "nine-to-five" workday.[17][18] Supporters have also argued that DST decreases energy consumption by reducing the need for lighting and heating, but the actual effect on overall energy use is heavily disputed.

The manipulation of time at higher latitudes (for example Iceland, Nunavut or Alaska) has little impact on daily life, because the length of day and night changes more extremely throughout the seasons (in comparison to other latitudes), and thus sunrise and sunset times are significantly out of sync with standard working hours regardless of manipulations of the clock.[19] DST is also of little use for locations near the equator, because these regions see only a small variation in daylight in the course of the year.[20]

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"[46] and pundits have dubbed it "Daylight Slaving Time".[47] Historically, retailing, sports, and tourism interests have favored daylight saving, while agricultural and evening entertainment interests have opposed it, and its initial adoption had been prompted by energy crisis and war.[48]

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. However, the opposition was stronger: it included Prime Minister H. H. Asquith, Christie (the Astronomer Royal), George Darwin, Napier Shaw (director of the Meteorological Office), many agricultural organizations, and theater owners. After many hearings the proposal was narrowly defeated in a Parliament committee vote in 1909. Willett's allies introduced similar bills every year from 1911 through 1914, to no avail.[49] The US was even more skeptical: Andrew Peters introduced a DST bill to the US House of Representatives in May 1909, but it soon died in committee.[50]

After Germany led the way with starting DST (German: Sommerzeit) during World War I on 30 April 1916 together with its allies to alleviate hardships from wartime coal shortages and air raid blackouts, the political equation changed in other countries; the United Kingdom used DST first on 21 May 1916.[51] US retailing and manufacturing interests led by Pittsburgh industrialist Robert Garland soon began lobbying for DST, but were opposed by railroads. The US's 1917 entry to the war overcame objections, and DST was established in 1918.[52]

The 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.[39] The US 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.[53] Only a few US cities retained DST locally thereafter,[54] including New York so that its financial exchanges could maintain an hour of arbitrage trading with London, and Chicago and Cleveland to keep pace with New York.[55] Wilson's successor Warren G. Harding opposed DST as a "deception". 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. Some businesses followed suit though many others did not; the experiment was not repeated.[14]

Since Germany's adoption in 1916 the world has seen many enactments, adjustments, and repeals of DST, with similar politics involved.[56]

The history of time in the United States includes DST during both world wars, but no standardization of peacetime DST until 1966.[57][58] In May 1965, for two weeks, St. Paul, Minnesota and Minneapolis, Minnesota were on different times, when the capital city decided to join most of the nation by starting Daylight Saving Time while Minneapolis opted to follow the later date set by state law.[59] 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 US DST, and both Idaho senators voted for it based on the premise that during DST fast-food restaurants sell more French fries, which are made from Idaho potatoes.[3]

In 1992 after a three-year trial of daylight saving in Queensland, Australia, a referendum on daylight saving was held and defeated with a 54.5% 'no' vote with regional and rural areas strongly opposed, while those in the metropolitan south-east were in favor.[60] In 2005, the Sporting Goods Manufacturers Association and the National Association of Convenience Stores successfully lobbied for the 2007 extension to US DST.[61] In December 2008, the Daylight Saving for South East Queensland (DS4SEQ) political party was officially registered in Queensland, advocating the implementation of a dual-time zone arrangement for Daylight Saving in South East Queensland while the rest of the state maintains standard time.[62] DS4SEQ contested the March 2009 Queensland State election with 32 candidates and received one percent of the statewide primary vote, equating to around 2.5% across the 32 electorates contested.[63] After a three-year trial, more than 55% of Western Australians voted against DST in 2009, with rural areas strongly opposed.[64] On 14 April 2010, after being approached by the DS4SEQ political party, Queensland Independent member Peter Wellington, introduced the Daylight Saving for South East Queensland Referendum Bill 2010 into Queensland Parliament, calling for a referendum to be held at the next State election on the introduction of daylight saving into South East Queensland under a dual-time zone arrangement.[65] The Bill was defeated in Queensland Parliament on 15 June 2011.[66]

In the UK the Royal Society for the Prevention of Accidents supports a proposal to observe SDST's additional hour year-round, but is opposed in some industries, such as postal workers and farmers, and particularly by those living in the northern regions of the UK.[12]

In some Muslim countries DST is temporarily abandoned during Ramadan (the month when no food should be eaten between sunrise and sunset), since the DST would delay the evening dinner. Ramadan took place in July and August in 2012. This concerns at least Morocco[67][68] and Palestine, although Iran keeps DST during Ramadan.[69] Most Muslim countries do not use DST, partially for this reason.

The 2011 declaration by Russia that it would not turn its clocks back and stay in DST all year long was subsequently followed by a similar declaration from Belarus.[70] The plan generated widespread complaints due to the dark of wintertime morning, and thus was abandoned in 2014.[71] The country changed its clocks to Standard Time on 26 October 2014 - and intends to stay there permanently.[72]

Public safety

In 1975 the US DOT conservatively identified a 0.7% reduction in traffic fatalities during DST, and estimated the real reduction at 1.5% to 2%,[101] but the 1976 NBS review of the DOT study found no differences in traffic fatalities.[15] In 1995 the Insurance Institute for Highway Safety estimated a reduction of 1.2%, including a 5% reduction in crashes fatal to pedestrians.[102] Others have found similar reductions.[103] 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.[104] However, accidents do increase by as much as 11% during the two weeks that follow the end of British Summer Time.[105] It is not clear whether sleep disruption contributes to fatal accidents immediately after the spring clock shifts.[106] A correlation between clock shifts and traffic accidents has been observed in North America and the UK but not in Finland or Sweden. If this effect exists, it is far smaller than the overall reduction in traffic fatalities.[107] A 2009 US study found that on Mondays after the switch to DST, workers sleep an average of 40 minutes less, and are injured at work more often and more severely.[108]

In the 1970s the US Law Enforcement Assistance Administration (LEAA) found a reduction of 10% to 13% in Washington, D.C.'s violent crime rate during DST. 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".[109] Outdoor lighting has a marginal and sometimes even contradictory influence on crime and fear of crime.[110]

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. Similar twice-yearly tasks include reviewing and practicing fire escape and family disaster plans, inspecting vehicle lights, checking storage areas for hazardous materials, reprogramming thermostats, and seasonal vaccinations.[111] Locations without DST can instead use the first days of spring and autumn as reminders.

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