Encyclopedia
Daylight saving time , 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 summer months. This is intended to provide a better match between the hours of daylight and the active hours of work and school. The "saved" daylight is spent on evening activities which get more daylight, rather than being "wasted" while people sleep past dawn.
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 .
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 becomes Central European Summer Time .
The word "summer" in this context includes most of spring after the spring equinox and nearly all 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 by
Benjamin Franklin in a letter to the editors of the
Journal of Paris.
However, as the article was humorous it is not clear whether Franklin was seriously proposing that the French adopt it, or simply that that people should get up and go to bed earlier.
It was first seriously proposed by
William Willett in the , 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 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, in which Congress overrode 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. Since 2002, the
European Union has fixed the last Sunday in March and the last Sunday in October as start and end dates .
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 late 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 , and crime reduction .
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 spike in the number of severe auto accidents, 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.
Many also point to the fact that the actual time change causes confusion and ambiguity. For example, 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. On a more trivial note, this also means that people born during one of those two hours have no way to know which one it really was, unless someone such as a parent bothers to make a note of it; birth certificates rarely keep track of this. A British politician, Lord Balfour, noted: "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.
Most Windows-based computers reset their internal clocks to DST automatically. Many Linux based computers set their internal clocks to "Zulu Time" and apply a compensation factor that depends on the time zone and daylight saving time status of the current user.
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 , regardless of daylight saving time.
Mnemonic
The
mnemonic "spring forward, fall back" 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 no longer 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 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 .
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. . For example, DST ends on the last Sunday in October, regardless of year. When the rule changes , 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 . 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 "" 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 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 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 can be represented. This database is separate from the underlying operating system 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 . 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 . At this date, the same hour occurs twice, first in daylight time, and then in standard 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 . The change is at midnight ; 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 to not 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 used DST briefly when it was war time with Pakistan and China.
Iran
Before 1979, DST was observed in Iran. Thereafter it was abandoned until 1989, when it started on the first day of Farvardin in the
Iranian calendar and ended on the first day of Mehr . In 2006, Iran stopped observing DST.
Israel
Israel observes DST starting on the last Friday before April 2 and ending at 2 a.m. 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 one occasion, terrorists were transporting a bomb that they mistakenly thought was set to go off at 5:30 p.m. Israeli Time; it was actually set for 5:30 p.m. Palestinian Time, which was an hour ahead. As a result, the bomb went off while the bombs were still being transported, killing them .
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.
Kyrgyzstan
Kyrgyzstan voted to stop observing DST in 2005 by remaining on UTC+6 as Standard 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 and
Fidel Ramos . 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 .
Taiwan
Taiwan, Republic of China 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. All these states end DST on the last Sunday in March.
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 each defeated by a small margin. See also:
Time in Australia and
New Zealand
DST begins at 2 a.m. NZST on the first Sunday in October each year, and ends at 3 a.m. NZDT 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, EST ended on the last Sunday of September. In the West European , Central European , and East European 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.
Russia and the former USSR
In the
USSR daylight saving 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 , 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 .
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 to 3:00 LDT 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 .
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.
Manitoba begins DST at 02:00, but switches back to standard time in October at 03:00.
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. Note, that 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 , yet clocks are kept at UTC-6 all year long. Thus, while Saskatchewan is always on Central Standard Time, in the summer months this matches adjacent areas that are on Mountain Daylight Time to the west & 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 . 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 . This includes Fort St. John, Charlie Lake, Taylor and Dawson Creek. The
Crowsnest corridor between Creston and Yahk in the East Kootenays 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.
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 it's 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
The schedule for 2006 in the
United States is that DST began on the first Sunday in April , and changes back to standard time on the last Sunday in October . The time is adjusted at 2 AM.
Beginning in 2007, DST will start on the second Sunday in March , and change back to standard time on the first Sunday in November . 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 back to the DST schedule set in 1986 if it cannot be shown that there are significant energy savings from an extension of DST.
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.
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 .
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 in the former year and the last Sunday in February 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 and
Edward Markey 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 and
Pete Domenici 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.
An additional issue raised by this extension is that it may require the reconfiguration of some computers. Many computers are programmed to adjust automatically for DST, but do so based on static tables stored directly on the computer itself. In order to change the dates and times at which the automatic jump to or from DST occurs, these tables must be modified, or the user must manually specify that the computer's clock should operate in DST mode. One potential issue related to this is the amount of labor and money that may be spent correcting errors that arise due to a
failure to update computers. Certain types of information systems may encounter problems arising from a lack of synchronization unless both computers and databases are carefully updated.
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 occuring as late as 3:00 P.M. by the clock in a place like Nome. Others argue that ending daylight savings 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 . 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.
Indiana
See also
Time in IndianaFor the last several decades, 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.
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. Since Nevada is on the
Pacific Time Zone, it would have made Nevada unusual in that travelers crossing the stateline at Utah during Daylight Saving Time would have a 2-hour time shift and it would place Nevada an hour behind California, its western neighbor. 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
Chile
Chile switches to DST at midnight at the end of the second Saturday in October and reverts to
Local Standard Time 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 . Starting and ending dates are variable: normally DST starts at midnight on an October 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 18th 2007 States bellow: Rio Grande do Sul, Santa Catarina, Parana, Sao Paulo, Rio de Janeiro, Espirito Santo, Minas Gerais, Goias, Matto Grosso, Matto Grosso do Sul and Distrito Federal.
Paraguay
Paraguay observes DST. This year DST will start on October 15th 2006 and it will end on March 11th 2007.
Uruguay
Since 2004 Uruguay observes DST. This year DST will start on October 1st 2006 and it will end on March 11th 2007.
Peru
Peru experimented with DST for one year during the 1990s; it is no longer observed.
Notes
See also
- Eastern Daylight Time
- Central Daylight Time
- List of countries that do not observe Daylight Saving Time
- Zoneinfo
Books
- Prerau, David.
- Prerau, David. — The Story of Summer Time/Daylight Saving time with a focus on the UK
- Downing, Michael.
External links
- - United States DST schedule , explanation, history
- by JR Stockton. With future changeover dates EU
- examines daylight saving in Australia.
- - Time calculation services
