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Daylight saving time (DST), also known as summer time or, daylight savings time, is a widely used system of adjusting the official local time forward, usually by one hour from its official standard time, for the spring, summer, and early autumn periods.

DST is most commonly used in temperate regions, due to the considerable variation in the amount of daylight versus darkness across the seasons in those regions.

Governments often tout it as an energy conservation measure, on the grounds that it allows more effective use of natural sunlight resource in summer time. Since there is less darkness in the "waking day", there is less use of electric lights. Some opponents reject this argument (see below, Criticism).

Europeans commonly refer to the system as summer time: Irish Summer Time, British Summer Time, and European Summer Time. This is reflected in the time zones names as well, e.g., Central European Time (CET) becomes Central European Summer Time (CEST).

The word "summer" in this context includes most of spring after the spring equinox and a large part of autumn. Likewise, the word "winter" here includes part of autumn and a few weeks in spring. This varies by time zone, of course, and can change over time as well.

Origin

DST was first mentioned in 1784 by Benjamin Franklin in a letter to the editors of the Journal of Paris. However, as the satirical article was humorous, it is extremely clear Franklin couldn't seriously propose that the French adopt it. The mere suggestion that a tax be levied on those who have their shades drawn during daylight hours, or simply that people should get up and go to bed earlier is ludicrous.

It was first seriously proposed by William Willett in the "Waste of Daylight", published in 1907, but he was unable to get the British government to adopt it, despite considerable lobbying.

The idea of DST was first put into practice by the German government during the First World War, between April 30, 1916 and October 1, 1916. Shortly afterward, the United Kingdom followed suit, first adopting it between May 21 and October 1, 1916. On June 17, 1917 Newfoundland became the first North American jurisdiction to adopt DST with the passing of the Daylight Saving Act of 1917. On March 19, 1918, the U.S. Congress established several time zones, which had been in use by railroads and most cities since 1883 and made DST official, effective March 31, for the remainder of World War I. It was observed for seven months in 1918 and 1919. The law, however, proved so unpopular, mostly because people rose and went to bed earlier than in current times, that it was repealed in 1919, when Congress overrode President Woodrow Wilson's veto of the repeal.

Observation of DST

DST is generally a temperate zone practice; day lengths in the tropics do not vary enough to justify DST. The amount of the time shift varies, but one hour is the most common. The dates of the beginning and ending of DST also vary by country. With a few exceptions, switchovers between standard time and DST generally occur in the early hours of a Sunday morning, because doing so then causes less disruption than a change on a weekday would.

DST commonly begins in the northern hemisphere on the last Sunday in March or the first Sunday in April, and ends on the last Sunday in October. However, beginning in 2007, the United States will begin observing DST from the second Sunday in March until the first Sunday in November. (Studies will determine if this remains permanent.) Since 2002, the European Union has fixed the last Sunday in March and the last Sunday in October as start and end dates (European Summer Time).

In the southern hemisphere, the beginning and ending dates are switched; therefore, the time difference between the United Kingdom and Chile may be three, four or five hours, depending on the time of year.

Rationales for DST

One of the major reasons given for observing DST is energy conservation. Theoretically, the amount of residential electricity needed in the evening hours is dependent both on when the sun sets and when people go to bed. Because people tend to observe the same bedtime year-round, by artificially moving sunset one hour later, the amount of energy used is theoretically reduced. A 1975 United States Department of Transportation study showed that DST would theoretically reduce the country's electricity usage by 1% from March to April, if implemented during these months.

Part of the reason that it is normally observed in the early spring, summer, and early autumn instead of the winter months is that the amount of energy saved by experiencing sunset one hour later would be negated by the increased need for artificial morning lighting due to a later sunrise. During the summer most people would wake up after the sun rises, regardless of whether daylight saving time is in effect or not, so there is no increased need for morning lighting to offset the afternoon drop in energy usage.

Another perceived benefit of DST is increased opportunities for outdoor activities. Most people plan outdoor activities during the increased hours of sunlight. Other benefits cited include prevention of traffic injuries (by allowing more people to return home from work or school in daylight), and crime reduction (by reducing people's risk of being targets of crimes that are more common in dark areas).

When the U.S. went on extended DST in 1974 and 1975 in response to the 1973 energy crisis, Department of Transportation studies found that observing DST in March and April saved 10,000 barrels of oil a day, and prevented about 2,000 traffic injuries and 50 fatalities saving about U.S. $28 million in traffic costs.

Criticism of DST

DST is not universally accepted and many localities do not observe it. Opponents claim that there is not enough benefit to justify the need to adjust clocks twice every year. The disruption in sleep patterns associated with setting clocks either forward or backward correlates with a small increase in the number of fatal auto accidents, (cf. above estimate of net decrease in fatal auto accidents of 50) as well as lost productivity as sleep-disrupted workers adjust to the schedule change. It is also noted that much effort is spent reminding everyone twice a year of the change, and thousands are inconvenienced by showing up at the wrong time when they forget. Since DST exchanges morning daylight for evening daylight, late sunrises occur when DST is in effect either too far before the vernal equinox or too far after the autumnal equinox and darkness in the morning can be undesirable for early risers like schoolchildren and workers who must awaken at 6:30 a.m. or earlier.

There is also a question whether the decrease in lighting costs justifies the increase in summertime air conditioning costs. Workers arriving home to an empty house during hotter hours will need to use more energy to cool their house.

It is also speculated that one of the benefits—more afternoon sun—would also actually increase energy consumption as people get into their cars to enjoy more time for shopping and the like.

DST's twice-annual shifts in recorded time cause legal and business-operational complications, as shown in the following examples. During a North American time change, a fall night during which clocks are reset from 2 a.m. DST to 1 a.m. Standard Time, times between 1 a.m. and 2 a.m. will occur twice, causing confusion in transport schedules, payment systems, etc. DST's annual autumn shift in recorded time—which causes an hour of the same numerical name to be recorded twice—also means that people born during one of those two hours have no way to know which of standard time or DST was used to record the time of their birth, unless someone such as a parent makes a note of it; birth certificates rarely keep track of this. A British politician, Lord Balfour, noted the legal complications in British law: "Supposing some unfortunate Lady was confined with twins and the first child was born 10 minutes before 3 o'clock British Summer Time. ... the time of birth of the two children would be reversed. ... Such an alteration might conceivably affect the property and titles in that House."

Daylight saving time also causes much confusion with international business, people who commute across time zones, and computer networks that span multiple time zones. One particular problem for scheduling systems is that it makes the length of a day variable. Each year there is one 23 hour day and one 25 hour day, causing display and time tracking problems, especially when coordinating events between time zones.

Some studies do show that changing the clock increases the traffic accident rate. Following the spring shift to DST, when one hour of sleep is lost, there is a measurable increase in the number of traffic accidents that result in fatalities.

People who work nights often have an extra hassle logging how many hours they worked, since it will be either one hour more or one hour less than the simple difference in start/stop times.

DST is particularly unpopular among people working in agriculture because they must rise with the sun regardless of what the clock says, and thus the people are placed out of synchronization with the rest of the community, including school times, broadcast schedules, and the like.

Other critics suggest that DST is, at its heart, government paternalism and that people rise in the morning as a matter of choice because many people enjoy night-time hours and their jobs do not require them to make the most of daylight. Different people start their day at different times (office workers start their day later than factory workers, who start their day later than farm workers), regardless of daylight saving time.

The website www.standardtime.com has more info about DST, and why some believe it should be stopped.

Mnemonic

The mnemonic "spring forward, fall back" (also "spring up, fall back" or "spring ahead, fall behind") tells us how to reset clocks when the time changes. This uses the word "fall" to mean "autumn," a usage that is very common in American and Canadian English, though not so in British English.

Associated practices

Fire safety officials in Australia, Canada, New Zealand, and the United States encourage citizens to use the two annual time changes as a reminder to check the batteries in home and office fire alarms and smoke detectors. For example, the Country Fire Authority of Victoria in Australia has been running a program called "Change Your Clock, Change Your Smoke Alarm Battery" for several years. This is especially important in autumn, just before the heating season causes an increase in home fires.

Computer systems

Most modern computer operating systems include the capability to automatically change the local time when daylight saving starts and finishes. See the Time zone article for general information on time zones and computer systems. Israel, until a few years ago, observed DST on different dates each year, and as its new system relies on the Jewish lunar calendar, most computers do not handle Israel Summer Time (IST).

Microsoft Windows

The time zone database in most Windows-based computer systems stores only a single start and end rule for each zone, and daylight saving information is stored in the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones\, under the TZI registry value. (In Windows XP and Windows 2003, time-zone information is stored in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\). For example, DST ends on the last Sunday in October, regardless of year. When the rule changes (e.g. Australian DST ending one week later than usual in 2006, or DST being extended in the United States starting in 2007), an update needs to be applied. In the case of a single-year anomaly, a new time zone is created and used. Before the following year, the time zone will have to be switched back to the original. For permanent rule changes, the rule definition for the time zone can be changed without requiring a new time zone to be set up.

One of the problems of this approach is that software that uses time zone information will get incorrect results if referring to a year with rules that are different from those currently in the database. A good example is the Lotus Notes calendar system, which stores event times in UTC. Events created with calendar dates near DST start and end dates can have their local time interpretation changed after the time zone database is updated (i.e. after an operating system update is applied). Another issue was highlighted when the Australian government changed daylight saving time to end on April 2 instead of March 26, because of the 2006 Commonwealth Games. Microsoft did not modify the start and end rule for the time zones affected, but instead added new timezones with the words "(Commonwealth Games)" which caused various issues with many software applications, including Microsoft Outlook and several accounting packages. Workarounds for the issue were to use the Microsoft utility timezone to modify the start and finish of each affected timezone, then either reboot the computer or go into Date and Time in the Control Panel, click on the Time Zone tab and click on OK to force Windows to refresh its daylight saving time information.

Unix

Unix systems (including Linux and Mac OS X) typically use the Zoneinfo utility which allows a single time zone to have multiple DST rules to handle changes from year to year. As soon as a rule change is announced, it can be safely added to the system. All the standard library routines which calculate times access this database, so software that queries whether a particular date will have DST in effect (for the time zone of the process) will get the correct answers as long as the time zone rule is correct for the year in question.

Java

Java uses a similar database to Unix, so rules for multiple years (not just the current year) can be represented. This database is separate from the underlying operating system's time zone database, so it must also be updated when DST rules change.

Name

In the normative form of the name, "daylight saving" is a compound adjective that modifies "time." A common variant is daylight savings time, which is frequently heard in speech and appears in some dictionaries.

Hour interchange

• When DST begins, the day loses one hour (hour interchange of -1). At this date, a full hour is skipped and does not exist either before or after the transition, so this date includes only 23 hours.
• When DST ends, the day gains one hour (hour interchange of +1). At this date, the same hour occurs twice, first in daylight (summer) time, and then in standard (winter) time, so this date includes 25 hours. As such, October is the longest month in those places where DST ends in October, being 31 days and 1 hour long. In the Southern hemisphere, where DST commonly ends in March, that month is 31 days and 1 hour long.
• Note that some areas apply an offset of only one half-hour for their DST, such as Lord Howe Island: at the date of transition to DST, the legal day counts only 23 hours and 30 minutes, and at the date of transition back to standard time, the legal day counts 24 hours and 30 minutes.

Usage and history by location

Africa

Egypt

Egypt normally observes DST between the last Thursday in April and the last Thursday in September when the clocks are three hours ahead of Greenwich Mean Time (UTC+3). The change is at midnight (local time); i.e. one second after 23:59:59 on that Thursday becomes 23:00:00 Thursday. The date does not change when the first 00:00 midnight occurs, for all practical purposes, midnight does not occur until then. However, the 2006 rule is an exception: the clock falls back September 22 at 01:00 so as not to disrupt Ramadan, and possibly similar exceptions will apply in 2007 and 2008.

Namibia

DST begins on the first Sunday in September, and ends on the first Sunday in April.

Tunisia

Tunisia adopted Daylight savings Time for the first time in 2005 starting 1st May 2005 and following EU time schedules thereafter. This comes as a move by the government to try and promote saving of energy in the wake of the ever-rising cost of fuel in the world market.

Asia

China

The People's Republic of China experimented with DST from 1986, but abandoned it in the 1990s. The PRC now uses one time zone for the whole country; the size of the nation was a major factor why DST was not considered practical in China.

India

India never used DST

Iran

Before 1979, DST was observed in Iran. Thereafter it was abandoned until 1989, when it started on the first day of Farvardin (21-22 March) in the Iranian calendar and ended on the first day of Mehr (23-24 September). In 2006, Iran continued observing DST.

Israel

Israel observes DST starting on the last Friday before April 2 and ending at 2 AM on the Sunday between Rosh Hashanah and Yom Kippur. Until 2005, the schedule was variable: the only requirement was that there be at least 150 days per year of DST, and was set out each year by the Ministry of the Interior.

In territories controlled by the Palestinian National Authority, DST ends later, which can lead to some confusion. On September 5, 1999, terrorists were transporting a bomb that they mistakenly thought was set to go off at 5:30 PM Israel Standard Time; it was actually set for 5:30 PM Palestinian Daylight Time, which was an hour ahead. As a result, the bomb went off while the bomb was still being transported, killing the terrorists (and earning them a Darwin Award).

Japan

From 1948 to 1951, Japan observed DST between May and September every year. Since then, DST has never been implemented nationwide in Japan.

Jordan

Jordan UTC+2 observes daylight saving time from the end of March to the end of October.

Kazakhstan

Kazakhstan government made a decision to stop observing DST in 2005.

Kyrgyzstan

Kyrgyzstan voted to stop observing DST in 2005 by remaining on UTC+6 as Standard Time (which used to be Kyrgyzstan Summer Time) to still save energy.

Pakistan

Pakistan experimented with DST in 2002, going from +5:00 to +6:00 on the first Sunday in April at 00:01 to the first Sunday in October at 00:01. It has not used it since then.

Philippines

The Philippines experimented with DST for shorter periods during the presidencies of Corazon Aquino (1986 to 1992) and Fidel Ramos (1992 to 1998). DST was primarily intended to help deal with the country's energy crisis by minimizing the number of hours where electric lighting was to be used. On April 2006, the Philippine Department of Trade and Industry again proposed that DST be implemented to help deal with rising oil prices.

South Korea

South Korea observed DST from 1948 to 1951, from 1955 to 1960, and from 1987 to 1988. South Korea does not currently observe DST.

Syria

Syria observes DST at UTC+3, in 2006 from 30 March until 21 September (a change from 30 September).

Taiwan

Taiwan implemented DST from 1945 to 1961, revoked DST from 1962 to 1973, reinstated DST from 1974 to 1975, and revoked DST from 1976 onwards.

Australasia

Australia

In Australia, the decision to implement daylight saving time is left up to each state or territory. Some states or territories implement it and some do not.

New South Wales, Victoria, Tasmania, Australian Capital Territory and South Australia apply DST. Tasmania starts DST earlier than the others, beginning on the first Sunday in October, for other states it begins on the last Sunday in October. In all cases clocks are advanced one hour at 2 a.m. All these states end DST on the last Sunday in March at 3 a.m when clocks are set back one hour.

Western Australia, Northern Territory and Queensland do not have DST. Queensland experimented with it for a year or two in the early 1970s, and again in the 1990s, but it was not popular and was abandoned. Western Australia also tried daylight saving no fewer than six times between 1917 and 1992, resulting in three referendums at the end of each trial in the mid to late part of the 20th century. See also: Time in Australia and note.

This article documents a current event. Information may change rapidly as the event progresses, and initial news reports may be unreliable. The latest updates to this article may not reflect the most current information. Feel free to improve this article or discuss changes on the talk page, but please note that updates without valid and reliable references will be removed. (Learn how and when to remove this message)

NOTE: As of 25 October 2006, the Western Australian government is considering legislation to support Daylight Saving Time with a 3 year trial starting in December 2006 and eventually being put to referendum. Many Western Australians against DST have cried out against the trial, as there have been three referendums to date. . Supporters of DST, on the other hand, note that over the 15 years since the last referendum, many young people who would support it have reached voting age, and many more older people are likely to support it having moved with changes to society over that time.

New Zealand

DST begins at 2 a.m. NZST on the first Sunday in October each year, and ends at 3 a.m. NZDT (or 2 a.m. NZST as defined in the Time Act 1974) on the third Sunday in March.

New Zealand time, including DST, is used by several Antarctic bases that are supplied from New Zealand. This results in the oddity that the Amundsen-Scott South Pole Station sets its clocks an hour further ahead during the southern summer, when the sun is constantly above the horizon, than in the southern winter, when the sun is constantly below the horizon. The extreme geographic position of the base means that there is no possible adjustment of the daily activity cycle that can have any effect on the amount of sunlight received during those activities.

Europe

All countries in Europe except Iceland observe DST and change on the same date and time, starting on the last Sunday in March and ending on the last Sunday in October. Before 1996, DST ended on the last Sunday of September. In the West European (UTC), Central European (CET, UTC+1), and East European (UTC+2) time zones the change is simultaneous: on both dates the clocks are changed everywhere at 01:00 UTC, i.e. from local times of 01:00/02:00/03:00 to 02:00/03:00/04:00 in March, and vice versa in October. See also: European Summer Time and British Summer Time which includes description of Double Summer Time.

Russia and the former USSR

In the USSR daylight saving time (Moscow Summer Time) was introduced on April 1 1981 by a decision of the Council of Ministers of the USSR. In Russia it was not abandoned after the breakup of the USSR. The changeover dates in Russia are the same as for other European countries, but clocks are moved forward or back at 02:00 standard time in all zones. Thus in Moscow (local time = UTC+3 in winter, UTC+4 in summer), DST commences at 23:00 UTC on the day before the last Sunday in March, and ends at 23:00 UTC on the day before the last Sunday in October (note that "day before last Sunday" is not the same as "last Saturday" in a month where the last day is a Saturday).

Iceland

With Iceland observing UTC all year round despite being at a longitude which would indicate UTC-1, the country may be said to be on continuous DST. Polar or near-polar locations such as Iceland often opt out, as summer in these locations usually brings nearly uninterrupted daylight.

North America

North America generally follows the same procedure, with each time zone switching at 2:00 a.m. LST (local standard time) to 3:00 LDT (local daylight time) on the first Sunday in April, and again from 2:00 a.m. LDT to 1:00 LST on the last Sunday in October. In 2007, the starting and ending dates for DST will change in the United States and parts of Canada (see below).

The Canadian province of Newfoundland and Labrador is an exception in that the time changes take place at 00:01 local standard time and 00:01 local daylight time respectively. Also, in 1988, they experimented with Double Daylight Time, when the clocks went ahead by two hours, instead of the usual one hour.

Canada

In Canada, time is under provincial and territorial jurisdiction, not federal. The governments of Ontario, Manitoba, Quebec, Prince Edward Island, New Brunswick, Alberta, the Northwest Territories, British Columbia, Nova Scotia and Yukon Territory have so far pledged to change their DST rules to match the new U.S. rules. In 2007, their DST will start on the second Sunday in March, and return to standard time on the first Sunday in November. Newfoundland and Nunavut will continue to change time on the first Sunday in April and last Sunday in October unless they change their legislation. As noted below, Saskatchewan does not recognize DST.

Saskatchewan

The province of Saskatchewan is the largest part of the country that does not observe DST. Saskatchewan is bisected by the 105° West meridian, the central meridian of the Mountain Standard Time Zone (UTC-7), yet clocks are kept at UTC-6 all year long. (This policy was implemented when the Saskatchewan Time Act was passed in 1966, to solve the problems that arose when time zones varied from town to town.) Saskatchewan is always on Central Standard Time. In the summer months, this matches adjacent areas that are on Mountain Daylight Time to the west and south, and in the winter months, it matches areas that are on Central Standard Time to the east. Officially, the province is considered to be part of the Central time zone.

The charter of the city of Lloydminster, which is bisected by the Saskatchewan–Alberta boundary, gives it a special exception among areas in Saskatchewan to use DST. Lloydminster and its immediately surrounding region in Saskatchewan use the same timekeeping routine used by Alberta: DST with Mountain Standard Time. Local custom in Denare Beach and Creighton, SK, is to observe DST, thereby keeping the same time as nearby Manitoba communities.

Quebec

The eastern reaches of Quebec's North Shore, east of 63° West longitude, are in the Atlantic Time Zone, but do not observe DST (see exception, below). The effect is that in summer, their clocks match those of the rest of the province, which observes Eastern Daylight Time. In October, their clocks are rejoined by their Atlantic Standard Time neighbors. Although places east of 63° West are officially on Atlantic Time, local custom is to use Eastern Time as far east as the Natashquan River. Those communities observe DST, including all of Anticosti Island, which is bisected by the 63rd meridian.

British Columbia

Most of British Columbia observes DST, but there is a large tract in east-central BC in the Mountain Time Zone that does not (most of BC is on Pacific Time). This includes Fort St. John, Charlie Lake, Taylor and Dawson Creek. The Crowsnest corridor between Creston and Yahk in the East Kootenays (southeastern BC) also keeps standard time year-round.

Nunavut

While the rest of Nunavut observes DST, Southampton Island including Coral Harbour remain on Eastern Standard Time throughout the year.

Ontario

Secluded in the heart of northwestern Ontario, Pickle Lake and New Osnaburgh have no use for DST. To the south, Atikokan also ignores it, using Eastern Standard Time year-round, effectively adopting Central Daylight Time in summer. Southern Ontario including Toronto, however, does observe DST. The power utilities of Ontario also do not use DST.

Cuba

Since April 2004, Cuba has remained on DST. Cuba will end DST on October 29, 2006 and begin DST again on March 2007.

Guatemala

Guatemala started to use DST on April 30th 2006, ending on October 1st 2006. The implementation of DST has saved more than eight million dollars.

Honduras

Honduras adopted DST once from May 1994 until September 1994 but abandoned it that same year. On May 7th, 2006 it again used DST, however it ended on August 7th, 2006 making this the shortest use of DST in the northern hemisphere as it was only applied for 3 months. The government announced that the measure will be observed during the next three years 2007, 2008, 2009

Mexico

Mexico adopted DST nationwide in 1996, even in its tropical regions, because of its increasing economic ties to the United States. The Mexican state of Sonora has not observed DST since 1998 because its high temperatures observed during day resulting in more power usage from air conditioning units. Although the United States has changed the schedule for DST beginning in 2007, Mexico will not be going along with it. DST has often been a contentious issue in Mexico and is not likely to be expanded.

Nicaragua

Nicaragua observed DST since January 1st 1992 until February 20th 1994 but was stopped. On April 10th 2005 until October 2nd 2005 was implemented DST, this year the period has been similar began on April 30th 2006 and will be ending on October 1st 2006, this measure is for energy conservation

United States

In 2006

The schedule for 2006 in the United States is that DST began on the first Sunday in April (April 2, 2006), and changes back to standard time on the last Sunday in October (October 29, 2006). The time is adjusted at 2 AM.

From 2007

Beginning in 2007, DST will start on the second Sunday in March (March 11, 2007), and change back to standard time on the first Sunday in November (November 4, 2007). Under Section 110 of the Energy Policy Act of 2005, the U.S. Department of Energy is required to study the impact of the DST extension no later than nine months after the change takes effect. Congress has retained the right to revert to the DST schedule set in 1986 if it cannot be shown that there are significant energy savings from an extension of DST or if the extension may prove to be unpopular with the American public. One potential issue is that some northern regions on the western edge of time zones will for the first time since the 1974-75 "almost year round" DST experiment have sunrise times that occur after 8am.

History

DST was reinstated in the United States on February 9, 1942, again as a wartime measure to conserve resources. This remained in effect until World War II began winding down and the requirement was removed on September 30, 1945. During this period, the official designation "War Time" was used for year-round DST. The year-round War Time was double daylight saving time without reverting back to standard time during the winter months. When entering double daylight saving time, clocks are advanced two hours instead of one hour.

From 1945 to 1966, U.S. federal law did not address DST. States and localities were free to observe DST or not, and the predominant pattern was that the states and localities that did observe DST did so from the last Sunday in April to the last Sunday in September. In the mid-1950s, many states and localities in the northeastern United States began extending DST to the last Sunday in October. The absence of federal standardization resulted in a patchwork where some areas observed DST while adjacent areas did not, and it was not unheard of to have to reset a clock several times during a relatively short trip (e.g., bus drivers operating between Moundsville, West Virginia, and Steubenville, Ohio had to reset their watches seven times over 35 miles).

The U.S. federal Uniform Time Act became law on April 13, 1966 and it mandated that DST begin nationwide on the last Sunday in April and end on the last Sunday in October, effective in 1967. The act explicitly preempted all previously enacted state laws related to the beginning and ending of DST. Any state that wanted to be exempt from DST could do so by passing a state law, provided that it exempted the entire state. The law was amended in 1972 to permit states that straddle a time zone boundary to exempt the entire area of the state lying in one time zone. On July 8, 1986, President Ronald Reagan signed the Federal Fire Prevention and Control Act of 1986 into law that contained a daylight saving rider authored by Senator Slade Gorton. The starting date of DST was amended to the first Sunday in April effective in 1987. DST continued to end on the last Sunday in October.

While the states retain the capability to exempt themselves from DST, they are forbidden by federal law to increase a state's time spent on DST. Only the United States Congress may take such an action, as had twice occurred prior to 2006.

In response to the 1973 energy crisis, DST in the United States began earlier in both 1974 and 1975, commencing on the first Sunday in January (January 6) in the former year and the last Sunday in February (February 23) in the latter. The extension of daylight saving time was not continued due to public opposition to late sunrise times during the winter months. In 1976, the United States reverted back to the schedule set in the Uniform Time Act.

Starting March 11, 2007, DST will be extended another four to five weeks, from the second Sunday of March to the first Sunday of November. The change was introduced by Representatives Fred Upton (R-MI) and Edward Markey (D-MA) and added to the Energy Policy Act of 2005; the House had originally approved a motion that would have extended DST even further from the first Sunday in March to the last Sunday in November, but Senators Jeff Bingaman (D-NM) and Pete Domenici (R-NM) agreed to scale back the proposal in conference committee due to complaints from farmers and the airline industry. Proponents claimed that the extension would save "the equivalent of" 10,000 barrels of oil per day, but this figure was based on U.S. Department of Energy information from the 1970s, the accuracy and relevance of which the DoE no longer stands by. There is very little recent research on what the actual positive effects, if any, might be.

Since DST moves sunrise one hour later by the clock, late sunrise times become a problem when DST is observed either too far before the vernal equinox or too far after the autumnal equinox. Because of this, the extension was greeted with criticism by those concerned for the safety of children who would have been forced to travel to school before sunrise especially in the month of March before there is enough daylight in the morning to offset the morning darkness problem. In addition, the airline industry was especially concerned if DST were to be extended through to the last Sunday in November, as this is very often the Sunday after Thanksgiving. This is one of the busiest travel days at American airports, and could have resulted in much havoc among travelers who forgot that the clocks were changing that day.

If the original proposal to extend DST through the last Sunday in November had been adopted, the entire United States, with the exception of the states that exempted themselves, would have experienced the latest sunrises of the year during the month of November, which would have approached the extremely late sunrise times when DST went into effect on January 6 in 1974 due to the 1973 energy crisis.

Daylight Saving for Halloween

One bill that has been pushed for the past several years, especially by Wyoming Senator Michael Enzi, is the Halloween Safety Act to extend DST by one week to end on the first Sunday of November instead of the last Sunday in October. The idea was to allow children to go trick-or-treating in more daylight. This extension passed with the Energy Policy Act of 2005. Since trick-or-treating is primarily a nighttime activity, children will have one less hour between dusk and bedtime to conduct their trick-or-treating activities which could make this extension unpopular.

Template:US time 2006

Alaska

Alaska currently observes DST, but there is a statewide move to abolish it. As of July 24, 2006, Alaska's lieutenant governor Loren Leman approved a petition to collect signatures to put the initiative measure on the ballot by 2008. Due to Alaska's high latitude, Alaska has nearly round-the-clock daylight during summer and DST is seen by some Alaskans as unnecessary and a nuisance. Another issue is that the Alaskan mainland's single time zone is too wide and there is a large disparity between civil time and solar time with solar noon occurring as late as 3:00 P.M. by the clock in a place like Nome. Others argue that ending daylight saving time will place Alaska as much as five hours from Eastern Standard Time, making coordination of travel and phone conversations more difficult.

Arizona

Arizona did observe DST in 1967 under the Uniform Time Act when the state legislature did not enact an exemption statute that year. In March 1968, the DST exemption statute was enacted and the state of Arizona has not observed DST since 1967 (however, the large Navajo Indian Reservation, which extends from Arizona into two adjacent states, does). This is in large part due to energy conservation since the temperature in and around Phoenix and Tucson is hotter than any other large U.S. metropolitan area during the summer, resulting in more power usage from air conditioning units and evaporative coolers in homes and businesses. An extra hour of sunlight while people are active would cause people to run their cooling systems longer, thereby using more energy.

Colorado

At the end of the 20th century, Colorado Springs Gazette columnist Ralph Routon wrote a series of columns supporting the idea of placing all of Colorado on year-round DST in order to save state residents the "aggravation of resetting their clocks every six months." The idea gathered noticeable popular support within Colorado Springs, and attention of the state's larger newspapers, but when then state Senator MaryAnne Tebedo attempted to present the idea to the state legislature, her research uncovered Federal laws forbidding the state-initiated extension of daylight saving time. Still determined to relieve Coloradans of the need to change their clocks, Tebedo introduced the only bill legally permitted to her: a proposal to exempt the state of Colorado from DST. The bill failed to escape committee during the 2000 legislative session.

Hawaii

Because of Hawaii's tropical latitude, there is not a large variation in daylight length between winter and summer. Due to the location of Hawaiian archipelago, advancing the clock in Hawaii would have made sunrise times close to 7:00 A.M. even in June. (Most of inhabited islands are located close to the west end of the Hawaii-Aleutian time zone, but Oahu, Kauai and Niihau are located more than 7 1/2 degrees west of the Hawaii-Aleutian time zone's meridian and should be ideally located in the next time zone to the west. Hawaii did experiment with DST for three weeks between April 30, 1933 and May 21, 1933; there is no record as to why it was implemented or ultimately discontinued. Hawaii has never observed daylight saving time under the Uniform Time Act, having opted out of the Act's provisions in 1967.

Indiana

See also Time in Indiana

Since 1970, most of Indiana in the Eastern Time Zone did not observe Daylight Saving Time, but the entire state started to do so in April 2006 after eight counties in western Indiana were shifted from the Eastern Time Zone to the Central Time Zone.. One of the goals for observing DST was to get more Indiana counties observing the same timezone; formerly, 77 counties observed EST, 2 observed EST/EDT, and 13 observed CST/CDT. However, now Indiana has 18 counties observing Central Daylight Time while the remaining 74 counties observe Eastern Daylight Time.

Nevada

In 2005, Nevada Assembly Bill 18 would have exempted Nevada from Daylight Saving Time. The bill's author, Assemblyman Bob McCleary, D-North Las Vegas, argued that because of southern Nevada's desert climate, it would reduce power usage during the peak summer months by reducing the time that people would operate their home air conditioners. The result of not observing DST, however, would place the state in an odd time configuration relative to neighboring states. Because it is on the eastern edge of the Pacific Time Zone, Nevada (PST) would be two hours behind Utah (MDT), its eastern neighbor, and one hour behind California (PDT), its western neighbor. In the summer, it would therefore be the same time in Nevada (PST) as it would be in the majority of Alaska (AKDT). The bill died without a vote.

United States of America Territories

The following United States of America territories do not follow DST: American Samoa, Guam, Puerto Rico, the U.S. Virgin Islands

South America

Colombia

In 1991 Colombia experienced problems with electricity distribution and generation due to the "El Niño" phenomenon so the government decided using DST to help save electricity. The experience did not have good results due to the low latitude, therefore it is no longer observed.

Chile

Chile switches to DST at midnight at the end of the second Saturday in October and reverts to Local Standard Time (LST) at midnight at the end of the second Saturday the following March. The current law, which affects the entire country, was enacted in 1970, but it had observed the practice as early as 1927 when the country had been divided into two time zones. In specific years the starting and ending dates have been modified for political or climatic reasons. This year Chile will start DST on October 15th and it will be ending on March 11th 2007.

Brazil

Brazil adopted DST for the first time in 1931, and has used it continually since 1985 in southern states (south, southeast regions and states of Goiás and Mato Grosso do Sul), and until 2004, in Bahia. Starting and ending dates are variable: normally DST starts at midnight on an October (rarely November) Sunday and ends at midnight on a February or March Sunday. This year DST will start on November 5th 2006 and it will end on February 25th 2007 in the states of Rio Grande do Sul, Santa Catarina, Paraná, São Paulo, Rio de Janeiro, Espirito Santo, Minas Gerais, Goiás, Mato Grosso, Mato Grosso do Sul and Distrito Federal.

Paraguay

Paraguay observes DST. This year DST will start on October 15 2006 and it will end on March 11 2007.

Uruguay

Since 2004, Uruguay has observed DST. Starting in 2006, DST will start on the first Sunday in October and end on the second Sunday in March of every year.

Peru

Peru experimented with DST for one year during the 1990s; it is no longer observed.

Trivia

DST inspired the musical standard "(There Ought To Be A) Moonlight Saving Time" by Irving Kahal and Harry Richman. The song was made famous by Guy Lombardo, Maurice Chevalier, and others.

References

1. Read the full text of Essay on Daylight Saving.
2. Franklin's dictum "early to bed, early to rise, makes a man healthy, wealthy, and wise" urged his fellow countrymen to work during daylight and sleep after dark, saving money on candles. Benjamin Franklin: America's Inventor
3. Study by US Department of Transportation
4. "Fatal accidents following changes in daylight savings time: the American experience", Jason Varughese and Richard P. Allen. March 28, 2000. URL accessed August 15, 2006.
5. "Sleep Deprivation, Psychosis and Mental Efficiency"], Stanley Corren, PhD. March 1998. URL accessed September 22, 2006.
6. The Epoch Times "Daylight Saving Time Change Upcoming" Lord Balfour quote. "Supposing some unfortunate Lady was confined with twins..."
7. Ferguson, S.A. et al. (1995) Daylight saving time and motor vehicle crashes: the reduction in pedestrian and vehicle occupant fatalities. American Journal of Public Health 85, 92–95.
8. "History & Info - Daylight Saving Time", 21 October 2006,
9. Microsoft Download: Australian Daylight Savings Changes for Microsoft Products for the Year 2006; & MS-KB article 909915, "Microsoft products do not reflect Australian daylight saving time changes for the year 2006" - February 27, 2006
10. Aussie Microsoft calendar mess. Office Watch, volume 11 no. 5, 25 January 2006.
11. "daylight saving time." Merriam-Webster Online Dictionary, accessed July 13, 2006. "called also daylight saving, daylight savings, daylight savings time, daylight time"
12. daylight-saving time. The American Heritage Dictionary of the English Language, 4th ed., accessed July 13, 2006. "Variant Forms: or daylight-savings time"
13. Elham: Cabinet nullifies decision on daylight saving time
14. Daylight Saving Time in Middle East
15. Living on Zionist Time — 1999 Darwin Awards
16. Elaine Ruzul S. Ramos (2006-04-26). "DST in the works". Manila Standard Today. Retrieved 2006-09-10. {{cite web}}: Cite has empty unknown parameters: |accessyear=, |month=, |accessmonthday=, and |coauthors= (help)
17. Ronnell W. Domingo (2006-04-25). "NPCC: Don't hike prices on account of oil". Philippine Daily Inquirer. Retrieved 2006-09-10. {{cite web}}: Cite has empty unknown parameters: |accessyear=, |month=, |accessmonthday=, and |coauthors= (help)
18. Daylight Saving by Australian Government
20. "Directive 2000/84/EC of the European Parliament and of the Council of [[19 January]] [[2001]] on summer-time arrangements". EU.int. Retrieved 2006-03-27. {{cite web}}: URL–wikilink conflict (help)
21. Time System in Saskatchewan
22. Ralph Routon's column, "Year-round Daylight Time is Not an Option", Gazette, The (Colorado Springs), 29 January 2000, makes note of this in passing, but unfortunately does not identify the Act responsible
23. It is also possible that the extension may not last if there are no proven energy savings from the change as Congress retains the right to revert back to the schedules set in 1986 after a study of the change is complete. One potential problem of the change is that early March sunrise times under DST would be just as late as those in early January under standard time and late October under DST. Because the difference in sunrise times would occur suddenly rather than gradually, this move could prove to be unpopular with the American public as more people are forced to awaken in darkness quite suddenly and are drowsy as a result. Extending DST past Halloween may prove to be unpopular since evening darkness is associated with the mood of Halloween. Children who wait for darkness to fall to begin trick-or-treating would have one less hour to do so before bedtime.More Daylight Savings: Energy Boon or Scheduling Snafu?
24. Routon mentions in his original column, "Let's Make Daylight Time Year-Round" Gazette, The (Colorado Springs), 23 October 1999, several other beneficial effects, at least to himself
25. said attention being negative, as Ed Quillen savaged the plan in his articlePlot to Eliminate the Mountain Time Zone, Denver Post, 7 November 1999,
26. "Year-round Daylight Time is Not an Option" Gazette, The (Colorado Springs), 29 January, 2000: Routon mentions Tebedo's intent to introduce the bill
27. HawaiiAnswers.com: Has Hawaii ever been on daylight saving time, even for a very short time? If yes, when? The page cites The American Atlas, 5th ed., by Thomas Shanks. It is also worth noting that at one time Hawaii Standard Time was UTC-10:30.
28. Hawaii Revised Statutes, §1-31
29. Standard Time Zone Boundary in the State of Indiana (a 139 KB PDF file)
30. Las Vegas Review-Journal (Ed Vogel) Assembly panel likely to let Daylight Saving Time bill die 05 April 2005

See also

• Eastern Daylight Time
• Central Daylight Time
• List of countries that do not observe Daylight Saving Time
• Zoneinfo

Books

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

External links

• A Brief History of Daylight Saving Time
• Congressional Research Service (CRS) Reports regarding DST
• DST by WebExhibits
• EU directive 2000/84/EC
• Saving Time, Saving Energy - United States DST schedule (including new rules starting in 2007), explanation, history
• Impacts on Operating Systems and Applications due to new DST schedule starting in 2007
• Sources for daylight saving time data, including histories and predictions
• Summer Time by JR Stockton. With future changeover dates EU (until 2007 final, from then extrapolating)
• Sleep deficit and accidents
• National Association of Standard Time
• PhotoSydney: Daylight Saving examines daylight saving in Australia.
• www.TimeAndDate.com - Time calculation services
• www.thetimeworld.com Daylight-saving time with future changeover dates world-wide

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• Current events
• Time zones
• Benjamin Franklin