Daylight saving time

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"DST" redirects here. Daylight saving time_sentence_0

For other uses, see DST (disambiguation). Daylight saving time_sentence_1

Daylight saving time (DST), also daylight savings time or daylight time (the United States and Canada) and summer time (United Kingdom, European Union, and others), is the practice of advancing clocks during warmer months so that darkness falls later each day according to the clock. Daylight saving time_sentence_2

The typical implementation of DST is to set clocks forward by one hour in the spring ("spring forward") and set clocks back by one hour in autumn ("fall back") to return to standard time. Daylight saving time_sentence_3

As a result, there is one 23-hour day in late winter or early spring and one 25-hour day in the autumn. Daylight saving time_sentence_4

George Hudson proposed the idea of daylight saving in 1895. Daylight saving time_sentence_5

The German Empire and Austria-Hungary organized the first nationwide implementation starting on April 30, 1916. Daylight saving time_sentence_6

Many countries have used it at various times since then, particularly since the 1970s energy crisis. Daylight saving time_sentence_7

DST is generally not observed near the equator, where sunrise and sunset times do not vary enough to justify it. Daylight saving time_sentence_8

Some countries observe it only in some regions; for example, parts of Australia observe it, while other parts do not, and the United States observes it, while Arizona does not. Daylight saving time_sentence_9

Only a minority of the world's population uses DST; Asia and Africa generally do not observe it. Daylight saving time_sentence_10

DST clock shifts sometimes complicate timekeeping and can disrupt travel, billing, record keeping, medical devices, heavy equipment, and sleep patterns. Daylight saving time_sentence_11

Computer software generally adjusts clocks automatically. Daylight saving time_sentence_12

Rationale Daylight saving time_section_0

Industrialized societies usually follow a clock-based schedule for daily activities that do not change throughout the course of the year. Daylight saving time_sentence_13

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. Daylight saving time_sentence_14

In contrast, an agrarian society's daily routines for work and personal conduct are more likely governed by the length of daylight hours and by solar time, which change seasonally because of the Earth's axial tilt. Daylight saving time_sentence_15

North and south of the tropics daylight lasts longer in summer and shorter in winter, with the effect becoming greater the further one moves away from the tropics. Daylight saving time_sentence_16

By synchronously resetting all clocks in a region to one hour ahead of standard time, 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. Daylight saving time_sentence_17

However, they will have one less hour of daylight at the start of each day, making the policy less practical during winter. Daylight saving time_sentence_18

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. Daylight saving time_sentence_19

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. Daylight saving time_sentence_20

The manipulation of time at higher latitudes (for example Iceland, Nunavut, Scandinavia 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 phase with standard working hours regardless of manipulations of the clock. Daylight saving time_sentence_21

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. Daylight saving time_sentence_22

The effect also varies according to how far east or west the location is within its time zone, with locations farther east inside the time zone benefiting more from DST than locations farther west in the same time zone. Daylight saving time_sentence_23

History Daylight saving time_section_1

Ancient civilizations adjusted daily schedules to the sun more flexibly than DST does, often dividing daylight into 12 hours regardless of daytime, so that each daylight hour became progressively longer during spring and shorter during autumn. Daylight saving time_sentence_24

For example, the Romans kept time with water clocks that had different scales for different months of the year; at Rome's latitude, the third hour from sunrise (hora tertia) started 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. Daylight saving time_sentence_25

From the 14th century onwards, equal-length civil hours supplanted unequal ones, so civil time no longer varied by season. Daylight saving time_sentence_26

Unequal hours are still used in a few traditional settings, such as some monasteries of Mount Athos and all Jewish ceremonies. Daylight saving time_sentence_27

Benjamin Franklin published the proverb "early to bed and early to rise makes a man healthy, wealthy, and wise", and published a letter in the Journal de Paris during his time as an American envoy to France (1776–1785) suggesting that Parisians economize on candles by rising earlier to use morning sunlight. Daylight saving time_sentence_28

This 1784 satire proposed taxing window shutters, rationing candles, and waking the public by ringing church bells and firing cannons at sunrise. Daylight saving time_sentence_29

Despite common misconception, Franklin did not actually propose DST; 18th-century Europe did not even keep precise schedules. Daylight saving time_sentence_30

However, this changed as rail transport and communication networks required a standardization of time unknown in Franklin's day. Daylight saving time_sentence_31

In 1810, the Spanish National Assembly Cortes of Cádiz issued a regulation that moved certain meeting times forward by one hour from May 1 to September 30 in recognition of seasonal changes, but it did not actually change the clocks. Daylight saving time_sentence_32

It also acknowledged that private businesses were in the practice of changing their opening hours to suit daylight conditions, but they did so of their own volition. Daylight saving time_sentence_33

New Zealand entomologist George Hudson first proposed modern DST. Daylight saving time_sentence_34

His shift-work job gave him leisure time to collect insects and led him to value after-hours daylight. Daylight saving time_sentence_35

In 1895, he presented a paper to the Wellington Philosophical Society proposing a two-hour daylight-saving shift, and considerable interest was expressed in Christchurch; he followed up with an 1898 paper. Daylight saving time_sentence_36

Many publications credit the DST proposal to prominent English builder and outdoorsman William Willett, who independently conceived DST in 1905 during a pre-breakfast ride when he observed how many Londoners slept through a large part of a summer day. Daylight saving time_sentence_37

Willett also was an avid golfer who disliked cutting short his round at dusk. Daylight saving time_sentence_38

His solution was to advance the clock during the summer months, and he published the proposal two years later. Daylight saving time_sentence_39

Liberal Party member of parliament Robert Pearce took up the proposal, introducing the first Daylight Saving Bill to the House of Commons on February 12, 1908. Daylight saving time_sentence_40

A select committee was set up to examine the issue, but Pearce's bill did not become law and several other bills failed in the following years. Daylight saving time_sentence_41

Willett lobbied for the proposal in the UK until his death in 1915. Daylight saving time_sentence_42

Port Arthur, Ontario, Canada was the first city in the world to enact DST, on July 1, 1908. Daylight saving time_sentence_43

This was followed by Orillia, Ontario, introduced by William Sword Frost while mayor from 1911 to 1912. Daylight saving time_sentence_44

The first states to adopt DST (German: ) nationally were those of the German Empire and its World War I ally Austria-Hungary commencing April 30, 1916, as a way to conserve coal during wartime. Daylight saving time_sentence_45

Britain, most of its allies, and many European neutrals soon followed. Daylight saving time_sentence_46

Russia and a few other countries waited until the next year, and the United States adopted daylight saving in 1918. Daylight saving time_sentence_47

Most jurisdictions abandoned DST in the years after the war ended in 1918, with exceptions including Canada, the UK, France, Ireland, and the United States. Daylight saving time_sentence_48

It became common during World War II, and was widely adopted in America and Europe from the 1970s as a result of the 1970s energy crisis. Daylight saving time_sentence_49

Since then, the world has seen many enactments, adjustments, and repeals. Daylight saving time_sentence_50

Procedure Daylight saving time_section_2

See also: Daylight saving time by country Daylight saving time_sentence_51

The relevant authorities usually schedule clock changes to occur at (or soon after) midnight, and on a weekend, in order to lessen disruption to weekday schedules. Daylight saving time_sentence_52

A one-hour change is customary, but twenty-minute and two-hour changes have been used in the past. Daylight saving time_sentence_53

In all countries that observe daylight saving time seasonally (i.e. during summer and not winter), the clock is advanced from standard time to daylight saving time in the spring, and they are turned back from daylight saving time to standard time in the autumn. Daylight saving time_sentence_54

The practice, therefore, reduces the number of civil hours in the day of the springtime change, and it increases the number of civil hours in the day of the autumnal change. Daylight saving time_sentence_55

For a midnight change in spring, a digital display of local time would appear to jump from 23:59:59.9 to 01:00:00.0. Daylight saving time_sentence_56

For the same clock in autumn, the local time would appear to repeat the hour preceding midnight, i.e. it would jump from 23:59:59.9 to 23:00:00.0. Daylight saving time_sentence_57

In most countries that observe seasonal daylight saving time, the clock observed in winter is legally named "standard time", in accordance with the standardization of time zones to agree with the local mean time near the center of each region. Daylight saving time_sentence_58

An exception exists in Ireland, where its winter clock has the same offset (UTC±00:00) and legal name as that in Britain (Greenwich Mean Time)—but while its summer clock also has the same offset as Britain's (UTC+01:00), its legal name is Irish Standard Time as opposed to British Summer Time. Daylight saving time_sentence_59

While most countries that change clocks for daylight saving time observe standard time in winter and DST in summer, Morocco observes (since 2019) daylight saving time every month but Ramadan. Daylight saving time_sentence_60

During the holy month (the date of which is determined by the lunar calendar and thus moves annually with regard to the Gregorian calendar), the country's civil clocks observe Western European Time (UTC+00:00, which geographically overlaps most of the nation). Daylight saving time_sentence_61

At the close of this month, its clocks are turned forward to Western European Summer Time (UTC+01:00), where they remain until the return of the holy month the following year. Daylight saving time_sentence_62

The time at which to change clocks differs across jurisdictions. Daylight saving time_sentence_63

Members of the European Union conduct a coordinated change, changing all zones at the same instant, at 01:00 Coordinated Universal Time (UTC), which means that it changes at 02:00 Central European Time (CET), equivalent to 03:00 Eastern European Time (EET). Daylight saving time_sentence_64

As a result, the time differences across European time zones remain constant. Daylight saving time_sentence_65

North America coordination of the clock change differs, in that each jurisdiction change at 02:00 local time, which temporarily creates unusual differences in offsets. Daylight saving time_sentence_66

For example, Mountain Time is, for one hour in the autumn, zero hours ahead of Pacific Time instead of the usual one hour ahead, and, for one hour in the spring, it is two hours ahead of Pacific Time instead of one. Daylight saving time_sentence_67

The dates on which clocks change vary with location and year; consequently, the time differences between regions also vary throughout the year. Daylight saving time_sentence_68

For example, Central European Time is usually six hours ahead of North American Eastern Time, except for a few weeks in March and October/November, while the United Kingdom and mainland Chile could be five hours apart during the northern summer, three hours during the southern summer, and four hours for a few weeks per year. Daylight saving time_sentence_69

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. Daylight saving time_sentence_70

Starting in 2007, most of the United States and Canada observed DST from the second Sunday in March to the first Sunday in November, almost two-thirds of the year. Daylight saving time_sentence_71

Moreover, the beginning and ending dates are roughly reversed between the northern and southern hemispheres because spring and autumn are displaced six months. Daylight saving time_sentence_72

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. Daylight saving time_sentence_73

In some countries time is governed by regional jurisdictions within the country such that some jurisdictions change and others do not; this is currently the case in Australia, Canada, Mexico, and the United States (formerly in Brazil, etc.). Daylight saving time_sentence_74

From year to year, the dates on which to change clock may also move for political or social reasons. Daylight saving time_sentence_75

The Uniform Time Act of 1966 formalized the United States' period of daylight saving time observation as lasting six months (it was previously declared locally); this period was extended to seven months in 1986, and then to eight months in 2005. Daylight saving time_sentence_76

The 2005 extension was motivated in part by lobbyists from the candy industry, seeking to increase profits by including Halloween (October 31) within the daylight saving time period. Daylight saving time_sentence_77

In recent history, Australian state jurisdictions not only changed at different local times but sometimes on different dates. Daylight saving time_sentence_78

For example, in 2008 most states there that observed daylight saving time changed clocks forward on October 5, but Western Australia changed on October 26. Daylight saving time_sentence_79

Politics and governments Daylight saving time_section_3

Daylight saving has caused controversy since it began. Daylight saving time_sentence_80

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" and pundits have dubbed it "Daylight Slaving Time". Daylight saving time_sentence_81

Retailing, sports, and tourism interests have historically favored daylight saving, while agricultural and evening entertainment interests have opposed it; its initial adoption was prompted by energy crises and war. Daylight saving time_sentence_82

The fate of Willett's 1907 proposal illustrates several political issues. Daylight saving time_sentence_83

It attracted many supporters, including Arthur Balfour, Churchill, David Lloyd George, Ramsay MacDonald, Edward VII (who used half-hour DST at Sandringham or "Sandringham time"), the managing director of Harrods, and the manager of the National Bank. Daylight saving time_sentence_84

However, the opposition was stronger, including Prime Minister H. Daylight saving time_sentence_85 H. Asquith, William Christie (the Astronomer Royal), George Darwin, Napier Shaw (director of the Meteorological Office), many agricultural organizations, and theatre owners. Daylight saving time_sentence_86

After many hearings, the proposal was narrowly defeated in a parliamentary committee vote in 1909. Daylight saving time_sentence_87

Willett's allies introduced similar bills every year from 1911 through 1914, to no avail. Daylight saving time_sentence_88

The U.S. was even more skeptical; Andrew Peters introduced a DST bill to the House of Representatives in May 1909, but it soon died in committee. Daylight saving time_sentence_89

Germany led the way by starting DST (German: ) during World War I on April 30, 1916 together with its allies to alleviate hardships from wartime coal shortages and air raid blackouts. Daylight saving time_sentence_90

The political equation changed in other countries; the United Kingdom used DST first on May 21, 1916. Daylight saving time_sentence_91

U.S. retailing and manufacturing interests led by Pittsburgh industrialist Robert Garland soon began lobbying for DST, but they were opposed by railroads. Daylight saving time_sentence_92

The U.S.'s 1917 entry to the war overcame objections, and DST was established in 1918. Daylight saving time_sentence_93

The war's end swung the pendulum back. Daylight saving time_sentence_94

Farmers continued to dislike DST, and many countries repealed it after the war, like Germany itself who dropped DST from 1919 to 1939 and from 1950 to 1979. Daylight saving time_sentence_95

Britain was an exception; it retained DST nationwide but adjusted transition dates over the years for several reasons, including special rules during the 1920s and 1930s to avoid clock shifts on Easter mornings. Daylight saving time_sentence_96

Now summer time begins annually on the last Sunday in March under a European Community directive, which may be Easter Sunday (as in 2016). Daylight saving time_sentence_97

The U.S. was more typical; Congress repealed DST after 1919. Daylight saving time_sentence_98

President Woodrow Wilson was also an avid golfer like Willett, and he vetoed the repeal twice but his second veto was overridden. Daylight saving time_sentence_99

Only a few U.S. cities retained DST locally, 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. Daylight saving time_sentence_100

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. Daylight saving time_sentence_101

He ordered District of Columbia federal employees to start work at 8 am rather than 9 am during the summer of 1922. Daylight saving time_sentence_102

Some businesses followed suit, though many others did not; the experiment was not repeated. Daylight saving time_sentence_103

Since Germany's adoption in 1916, the world has seen many enactments, adjustments, and repeals of DST, with similar politics involved. Daylight saving time_sentence_104

The history of time in the United States includes DST during both world wars, but no standardization of peacetime DST until 1966. Daylight saving time_sentence_105

St. Daylight saving time_sentence_106 Paul and Minneapolis, Minnesota, were on different times for two weeks in May 1965 when the capital city decided to switch to daylight saving time, while Minneapolis opted to follow the later date set by state law. Daylight saving time_sentence_107

In the mid-1980s, Clorox and 7-Eleven provided the primary funding for the Daylight Saving Time Coalition behind the 1987 extension to U.S. DST. Daylight saving time_sentence_108

Both senators from Idaho, Larry Craig and Mike Crapo, voted for it based on the premise that fast-food restaurants sell more French fries during DST, which are made from Idaho potatoes. Daylight saving time_sentence_109

A referendum on daylight saving was held in Queensland, Australia, in 1992, after a three-year trial of daylight saving. Daylight saving time_sentence_110

It was defeated with a 54.5% "no" vote, with regional and rural areas strongly opposed, while those in the metropolitan southeast were in favor. Daylight saving time_sentence_111

In 2005, the Sporting Goods Manufacturers Association and the National Association of Convenience Stores successfully lobbied for the 2007 extension to U.S. DST. Daylight saving time_sentence_112

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. Daylight saving time_sentence_113

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. Daylight saving time_sentence_114

After a three-year trial, more than 55% of Western Australians voted against DST in 2009, with rural areas strongly opposed. Daylight saving time_sentence_115

Queensland Independent member Peter Wellington introduced the Daylight Saving for South East Queensland Referendum Bill 2010 into the Queensland parliament on April 14, 2010, after being approached by the DS4SEQ political party, calling for a referendum at the next state election on the introduction of daylight saving into South East Queensland under a dual-time zone arrangement. Daylight saving time_sentence_116

The Bill was defeated in the Queensland parliament on June 15, 2011. Daylight saving time_sentence_117

In the UK, the Royal Society for the Prevention of Accidents supports a proposal to observe SDST's additional hour year-round, but that is opposed in some industries, such as postal workers and farmers, and particularly by those living in the northern regions of the UK. Daylight saving time_sentence_118

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. Daylight saving time_sentence_119

Iran maintains DST during Ramadan, but most Muslim countries do not use DST, partially for this reason. Daylight saving time_sentence_120

Russia declared in 2011 that it would stay in DST all year long, followed by a similar declaration from Belarus. Daylight saving time_sentence_121

Russia's plan generated widespread complaints due to the dark of winter time morning, and thus was abandoned in 2014. Daylight saving time_sentence_122

The country changed its clocks to standard time on October 26, 2014, and it intends to stay there permanently. Daylight saving time_sentence_123

Impacts Daylight saving time_section_4

Main article: Analysis of daylight saving time Daylight saving time_sentence_124

Proponents of DST generally argue that it saves energy, promotes outdoor leisure activity in the evening (in summer), and is therefore good for physical and psychological health, reduces traffic accidents, reduces crime or is good for business. Daylight saving time_sentence_125

A 2017 meta-analysis of 44 studies found that DST leads to electricity savings of 0.3% during the days when DST applies. Daylight saving time_sentence_126

Several studies have suggested that DST increases motor fuel consumption, but a 2008 United States Department of Energy report found no significant increase in motor gasoline consumption due to the 2007 United States extension of DST. Daylight saving time_sentence_127

An early goal of DST was to reduce evening usage of incandescent lighting, once a primary use of electricity. Daylight saving time_sentence_128

Although energy conservation remains an important goal, energy usage patterns have greatly changed since then. Daylight saving time_sentence_129

Electricity use is greatly affected by geography, climate, and economics, so the results of a study conducted in one place may not be relevant to another country or climate. Daylight saving time_sentence_130

Later sunset times from DST are thought to affect behavior, for example increasing participation in after-school sports programs or outdoor afternoon sports such as golf, and attendance at professional sporting events. Daylight saving time_sentence_131

Advocates of daylight saving time argue that having more hours of daylight between the end of a typical workday and evening induces people to consume other goods and services. Daylight saving time_sentence_132

Many farmers oppose DST, particularly dairy farmers as the milking patterns of their cows do not change with the time. Daylight saving time_sentence_133

and others whose hours are set by the sun. Daylight saving time_sentence_134

Young children often have difficulty getting enough sleep at night when the evenings are bright. Daylight saving time_sentence_135

DST also hurts prime-time television broadcast ratings, drive-ins and other theaters. Daylight saving time_sentence_136

It has been argued that clock shifts correlate with decreased economic efficiency, and that in 2000 the daylight-saving effect implied an estimated one-day loss of $31 billion on U.S. stock exchanges, Others have asserted that the observed results depend on methodology and disputed the findings, though the original authors have refuted points raised by disputers. Daylight saving time_sentence_137

A correlation between clock shifts and traffic accidents has been observed in North America and the UK but not in Finland or Sweden. Daylight saving time_sentence_138

Four reports have found that this effect is smaller than the overall reduction in traffic fatalities. Daylight saving time_sentence_139

DST likely reduces some kinds of crime, such as robbery and sexual assault, as fewer potential victims are outdoors after dusk. Daylight saving time_sentence_140

Artificial outdoor lighting has a marginal and sometimes even contradictory influence on crime and fear of crime. Daylight saving time_sentence_141

A 2017 study in the American Economic Journal: Applied Economics estimated that "the transition into DST caused over 30 deaths at a social cost of $275 million annually," primarily by increasing sleep deprivation. Daylight saving time_sentence_142

Opponents argue that DST disrupts human circadian rhythms (negatively impacting human health in the process), that it increases fatal traffic collisions, that the actual energy savings are inconclusive, and that DST increases health risks such as heart attack. Daylight saving time_sentence_143

Year-round standard time (not year-round DST) is proposed to be the preferred option for public health and safety. Daylight saving time_sentence_144

Clock shifts were found to increase the risk of heart attack by 10 percent, and to disrupt sleep and reduce its efficiency. Daylight saving time_sentence_145

Effects on seasonal adaptation of the circadian rhythm can be severe and last for weeks. Daylight saving time_sentence_146

DST's clock shifts have the obvious disadvantage of complexity. Daylight saving time_sentence_147

People must remember to change their clocks; this can be time-consuming, particularly for mechanical clocks that cannot be moved backward safely. Daylight saving time_sentence_148

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. Daylight saving time_sentence_149

The length of the calendar day becomes variable; it is no longer always 24 hours. Daylight saving time_sentence_150

Disruption to meetings, travel, broadcasts, billing systems, and records management is common, and can be expensive. Daylight saving time_sentence_151

During an autumn transition from 02:00 to 01:00, a clock reads times from 01:00:00 through 01:59:59 twice, possibly leading to confusion. Daylight saving time_sentence_152

Some clock-shift problems could be avoided by adjusting clocks continuously or at least more gradually—for example, Willett at first suggested weekly 20-minute transitions—but this would add complexity and has never been implemented. Daylight saving time_sentence_153

DST inherits and can magnify the disadvantages of standard time. Daylight saving time_sentence_154

For example, when reading a sundial, one must compensate for it along with time zone and natural discrepancies. Daylight saving time_sentence_155

Also, sun-exposure guidelines such as avoiding the sun within two hours of noon become less accurate when DST is in effect. Daylight saving time_sentence_156

Terminology Daylight saving time_section_5

As explained by Richard Meade in the English Journal of the (American) National Council of Teachers of English, the form daylight savings time (with an "s") was already in 1978 much more common than the older form daylight saving time in American English ("the change has been virtually accomplished"). Daylight saving time_sentence_157

Nevertheless, even dictionaries such as Merriam-Webster's, American Heritage, and Oxford, which describe actual usage instead of prescribing outdated usage (and therefore also list the newer form), still list the older form first. Daylight saving time_sentence_158

This is because the older form is still very common in print and preferred by many editors. Daylight saving time_sentence_159

("Although daylight saving time is considered correct, daylight savings time (with an "s") is commonly used.") Daylight saving time_sentence_160

The first two words are sometimes hyphenated (daylight-saving(s) time). Daylight saving time_sentence_161

Merriam-Webster's also lists the forms daylight saving (without "time"), daylight savings (without "time"), and daylight time. Daylight saving time_sentence_162

The Oxford Dictionary of American Usage and Style explains the development and current situation as follows: "Although the singular form daylight saving time is the original one, dating from the early 20th century—and is preferred by some usage critics—the plural form is now extremely common in AmE. Daylight saving time_sentence_163

[...] The rise of daylight savings time appears to have resulted from the avoidance of a miscue: when saving is used, readers might puzzle momentarily over whether saving is a gerund (the saving of daylight) or a participle (the time for saving). Daylight saving time_sentence_164

[...] Using savings as the adjective—as in savings account or savings bond—makes perfect sense. Daylight saving time_sentence_165

More than that, it ought to be accepted as the better form." Daylight saving time_sentence_166

In Britain, Willett's 1907 proposal used the term daylight saving, but by 1911 the term summer time replaced daylight saving time in draft legislation. Daylight saving time_sentence_167

The same or similar expressions are used in many other languages: Sommerzeit in German, zomertijd in Dutch, kesäaika in Finnish, horario de verano or hora de verano in Spanish, and in French. Daylight saving time_sentence_168

The name of local time typically changes when DST is observed. Daylight saving time_sentence_169

American English replaces standard with daylight: for example, Pacific Standard Time (PST) becomes Pacific Daylight Time (PDT). Daylight saving time_sentence_170

In the United Kingdom, the standard term for UK time when advanced by one hour is British Summer Time (BST), and British English typically inserts summer into other time zone names, e.g. Central European Time (CET) becomes Central European Summer Time (CEST). Daylight saving time_sentence_171

The North American English mnemonic "spring forward, fall back" (also "spring ahead ...", "spring up ...", and "... fall behind") helps people remember in which direction to shift the clocks. Daylight saving time_sentence_172

Computing Daylight saving time_section_6

Changes to DST rules cause problems in existing computer installations. Daylight saving time_sentence_173

For example, the 2007 change to DST rules in North America required that many computer systems be upgraded, with the greatest impact on e-mail and calendar programs. Daylight saving time_sentence_174

The upgrades required a significant effort by corporate information technologists. Daylight saving time_sentence_175

Some applications standardize on UTC to avoid problems with clock shifts and time zone differences. Daylight saving time_sentence_176

Likewise, most modern operating systems internally handle and store all times as UTC and only convert to local time for display. Daylight saving time_sentence_177

However, even if UTC is used internally, the systems still require external leap second updates and time zone information to correctly calculate local time as needed. Daylight saving time_sentence_178

Many systems in use today base their date/time calculations from data derived from the tz database also known as zoneinfo. Daylight saving time_sentence_179

IANA time zone database Daylight saving time_section_7

The tz database maps a name to the named location's historical and predicted clock shifts. Daylight saving time_sentence_180

This database is used by many computer software systems, including most Unix-like operating systems, Java, and the Oracle RDBMS; HP's "tztab" database is similar but incompatible. Daylight saving time_sentence_181

When temporal authorities change DST rules, zoneinfo updates are installed as part of ordinary system maintenance. Daylight saving time_sentence_182

In Unix-like systems the TZ environment variable specifies the location name, as in TZ=':America/New_York'. Daylight saving time_sentence_183

In many of those systems there is also a system-wide setting that is applied if the TZ environment variable is not set: this setting is controlled by the contents of the /etc/localtime file, which is usually a symbolic link or hard link to one of the zoneinfo files. Daylight saving time_sentence_184

Internal time is stored in time-zone-independent Unix time; the TZ is used by each of potentially many simultaneous users and processes to independently localize time display. Daylight saving time_sentence_185

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. Daylight saving time_sentence_186

For example, TZ='EST5EDT,M3.2.0/02:00,M11.1.0/02:00' specifies time for the eastern United States starting in 2007. Daylight saving time_sentence_187

Such a TZ value must be changed whenever DST rules change, and the new value applies to all years, mishandling some older timestamps. Daylight saving time_sentence_188

Permanent daylight saving time Daylight saving time_section_8

See also: Permanent time observation in the United States, Decree time in Russia, and Summer time in Europe § Future Daylight saving time_sentence_189

A move to permanent daylight saving time (staying on summer hours all year with no time shifts) is sometimes advocated and is currently implemented in some jurisdictions such as Argentina, Belarus, Saskatchewan, Yukon, Iceland, Kyrgyzstan, Magallanes and Chilean Antarctica Region, Malaysia, Morocco, Namibia, Singapore, Turkey, Turkmenistan and Uzbekistan. Daylight saving time_sentence_190

Advocates cite the same advantages as normal DST without the problems associated with the twice yearly time shifts. Daylight saving time_sentence_191

However, many remain unconvinced of the benefits, citing the same problems and the relatively late sunrises, particularly in winter, that year-round DST entails. Daylight saving time_sentence_192

Russia switched to permanent DST from 2011 to 2014, but the move proved unpopular because of the late sunrises in winter, so in 2014, Russia switched permanently back to standard time. Daylight saving time_sentence_193

The United Kingdom and Ireland also experimented with year-round summer time between 1968 and 1971, and put clocks forward by an extra hour during World War II. Daylight saving time_sentence_194

In the United States, the Florida, Washington, California, and Oregon legislatures have all passed bills to enact permanent DST, but the bills require Congressional approval in order to take effect. Daylight saving time_sentence_195

Maine, Massachusetts, New Hampshire, and Rhode Island have also introduced proposals or commissions to that effect. Daylight saving time_sentence_196

Although 26 states have considered making DST permanent, unless Congress changes federal law, states cannot implement permanent DST—states can only opt out of DST, not standard time. Daylight saving time_sentence_197

In September 2018, the European Commission proposed to end seasonal clock changes as of 2019. Daylight saving time_sentence_198

Member states would have the option of observing either daylight saving time all year round or standard time all year round. Daylight saving time_sentence_199

In March 2019, the European Parliament approved the commission's proposal, while deferring implementation from 2019 until 2021. Daylight saving time_sentence_200

As of October 2020, the decision has not been confirmed by the Council of the European Union. Daylight saving time_sentence_201

The council has asked the commission to produce a detailed impact assessment, but the Commission considers that the onus is on the Member States to find a common position in Council. Daylight saving time_sentence_202

As a result, progress on the issue is effectively blocked. Daylight saving time_sentence_203

Experts in circadian rhythms and sleep caution against permanent daylight saving time, recommending year-round standard time as the preferred option for public health and safety. Daylight saving time_sentence_204

Perceived problems with permanent DST Daylight saving time_section_9

Since daylight saving time creates the illusion of the sun rising and setting one hour later on the clock, but does not add any additional daylight, the already later sunrise times under standard time are pushed an hour later on the clock with daylight saving time. Daylight saving time_sentence_205

Late sunrise times can become unpopular in the winter months which essentially forces workers and schoolchildren to begin the day in darkness. Daylight saving time_sentence_206

In 1974 following the enactment of the Emergency Daylight Saving Time Act in the United States, there were complaints of children going to school in the dark and working people commuting and starting their work day in pitch darkness during the winter months. Daylight saving time_sentence_207

The complaints led to the repeal of the act in October 1974 when standard time was restored until February 23, 1975. Daylight saving time_sentence_208

In 1976, the United States returned to the schedule set under the Uniform Time Act of 1966. Daylight saving time_sentence_209

In 1971, year-round daylight time in the United Kingdom was abandoned after a 3-year experiment because of complaints about winter sunrise times. Daylight saving time_sentence_210

The same complaints also led to Russia abandoning DST and instituting standard time year round in 2014. Daylight saving time_sentence_211

By country and region Daylight saving time_section_10

Main article: Daylight saving time by country Daylight saving time_sentence_212

Daylight saving time_unordered_list_0

See also Daylight saving time_section_11

Daylight saving time_unordered_list_1


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Daylight saving time.