Daylight saving time
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A public service announcement for turning the clock back one hour at the end of daylight saving time |
Daylight saving time (DST), also known as
summer time and sometimes referred to as
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 (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 nearly all of autumn (April through October). Likewise, the word "winter" here includes part of autumn and a few weeks in spring (November through March). This varies by
time zone, of course, and can change over time as well.
DST was first mentioned by
Benjamin Franklin in a letter to the editors of the
Journal of Paris.
[Read the full text.]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.
[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 ]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 and
October 1,
1916. Shortly afterward, the
United Kingdom followed suit, first adopting it between
May 21 and
October 1,
1916. 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 later repealed.
DST is generally a temperate zone practice; day lengths in the
tropics do not vary enough to justify DST.
Hawaii and
Arizona will be the only
U.S. states that do not observe DST after 2006. Before and during 2006, parts of Southern Indiana (Dubois County and surrounding counties) did not participate in DST. (As of July 2006, some of the counties were still debating to use Eastern or Central time.)
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. If no energy savings can be shown from the extension after the
U.S. Department of Energy completes a study of impact of the change, Congress may revert back to the schedule set in 1986 under Section 110 of the
Energy Policy Act of 2005. 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 four, five or six hours, depending on the time of year.
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.
[Study by US Department of Transportation]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 (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.
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. While many people use more sunlight under DST, most people also experience more heat, which prompts many people to turn on the air conditioner during the warmer afternoon hours. When air conditioning was not widely available, the change did save energy; however, air conditioning is much more widespread now than it was several decades ago. Air conditioning often uses more energy than artificial lighting. It was for this reason that Arizona rejected DST and opted to stay on standard time all year.
It is also speculated that one of the benefitsâ€"more afternoon sunâ€"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. It is difficult to imagine anyone caring about this, but at least one aristocrat, Lord Balfour of the UK, has lodged a farfetched objection: "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."
[The Epoch Times "Daylight Saving Time Change Upcoming" Lord Balfour quote. "Supposing some unfortunate Lady was confined with twins..."]Daylight saving time also causes much confusion with international business, people who commute across time zones (especially those time zones that do not observe DST), 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" (the time at the prime meridian) and apply a compensation factor that depends on the time zone and daylight saving time status of the current user.
Some societies like India have a system of calculating one's Horoscope which critically depends on the time of birth. Such oriental systems will be thrown out of gear by the ambiguity in time.
Some studies do show that changing the clock increases the traffic accident rate.
[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, 92â€"95.] 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.
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
mnemonic "spring forward, fall back" (also "spring ahead, 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.
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.
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, timezone 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)"
[ 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] which caused various issues with many software applications, including
Microsoft Outlook[Aussie Microsoft calendar mess. Office Watch, volume 11 no. 5, 25 January 2006.] 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) mostly 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 time zone database, so it must also be updated when DST rules change.
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.
["daylight saving time." Merriam-Webster Online Dictionary, accessed July 13, 2006. "called also daylight saving, daylight savings, daylight savings time, daylight time"] [daylight-saving time. The American Heritage Dictionary of the English Language, 4th ed., accessed July 13, 2006. "Variant Forms: or daylight-savings time"]* 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.
Africa
Egypt
Egypt observes DST between the last Friday 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). Note: the date does not change when the first 0:00 midnight occurs.
(See also
24-hour clock)Example: 25-09-2006 23:59 -> 25-09-2006 24:00 -> 25-09-2006 23:00 ... 25-09-2006 23:59 -> 26-09-2006 00:00
Wrong change: 25-09-2006 23:59 -> 25-09-2006 24:00 -> 26-09-2006 00:00-> 26-09-2006 23:00 ... 26-09-2006 23:59 -> 27-09-2006 00:00
Namibia
DST begins on the first Sunday in September, and ends on the first Sunday in April.
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 during its wars 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 (21-22 March) in the
Iranian calendar and ended on the first day of Mehr (23-24 September). In 2006, Iran stopped observing DST.
[Elham: Cabinet nullifies decision on daylight saving time]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.
[Daylight Saving Time in Middle East]In territories controlled by The
Palestinian National Authority, DST ends a week earlier, which can lead to some confusion. On one occasion, terrorists were transporting a bomb that they thought was set to go off at 5 p.m. Palestinian (Daylight) Time, but which actually was set for 5 p.m. Israeli (Standard) Time, which was an hour ahead. As a result, the bomb went off, killing them (and earning them a
Darwin Award).
[Living on Zionist Time â€" 1999 Darwin Awards]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 (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.
South Korea
South Korea observed DST three times: from 1948 to 1951, from 1955 to 1960, and from 1987 to 1988. It is no longer observed now.
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, daylight saving time is a state/territory-based initiative. Some states/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, usually near the beginning of October.
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 trialled daylight savings no fewer than six times between 1917 and 1992, and resulted in three referendums each defeated by a small margin. See also:
Time in Australia and
[Daylight Saving by Australian Government]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 but
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 (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.
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 (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.
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 and
Nova Scotia 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. The remaining provinces and territories (
Newfoundland,
Yukon Territory,
Nunavut,
Saskatchewan where applicable) will continue to change time on the first Sunday in April and last Sunday in October unless they change their legislation.
=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.) Thus, in the summer months Saskatchewan is on Mountain Daylight Time and in the winter months it is on Central Standard Time. This is equivalent to the province being on Mountain Daylight Time or Central Standard Time year-round. 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.
[Time System in Saskatchewan] 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 BC 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.
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 29 2006, ending on
September 30 2006.
Honduras
Honduras observed DST once in 1994 but abandoned it that same year. On
May 7,
2006 it began observing DST , but again was abandoned early, on
August 6,
2006Mexico
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 borders on the U.S. state of Arizona, which also does not observe DST. 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.[
3]
United States
|
Ohio Clock in the U.S. Capitol being turned forward for the first daylight saving time in 1918 |
The schedule for 2006 in the
United States is that DST began on the first Sunday in April (
,
2006), and changes back to standard time on the last Sunday in October (
October ,
2006). 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 (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. 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.
[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] 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.
[ 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?]The extension was greeted with criticism by those concerned for the safety of children traveling to school in the dark before the late sunrise. 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.
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 (though difficult to quantify) 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 (those that schedule future events with reference to
UTC, for example) 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. Due to Alaska's high latitude, Alaska has nearly round-the-clock daylight during summer and DST is seen as unnecessary and a nuisance.[
4]
=Arizona
=Arizona does not observe DST (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 swamp coolers in homes and businesses. An extra hour of sunlight 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."
[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] The idea gathered noticeable popular support within Colorado Springs, and attention of the state's larger
newspapers,
[said attention being negative, as Ed Quillen savaged the plan in his articlePlot to Eliminate the Mountain Time Zone, Denver Post, 7 November 1999,] 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.
["Year-round Daylight Time is Not an Option" Gazette, The (Colorado Springs), 29 January, 2000: Routon mentions Tebedo's intent to introduce the bill]=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.[
5] (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.
[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.] Hawaii has never observed daylight saving time under the Uniform Time Act, having opted out of the Act's provisions in 1967.
[Hawaii Revised Statutes, §1-31]=Indiana
=
For the last several decades, most of Indiana did not observe Daylight Saving Time, but the entire state started to in April 2006.
[Standard Time Zone Boundary in the State of Indiana (a 139 KB PDF file)]South America
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.
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). 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.
*
Eastern Daylight Time*
Central Daylight Time*
List of countries that do not observe Daylight Saving Time*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 U.K.
*Downing, Michael.
Spring Forward: The Annual Madness of Daylight Saving Time (Shoemaker & Hoard; ISBN 1-59376-053-1)
*
A Brief History of DST*
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
*
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
