Daylight saving time
Daylight saving time (also called DST, or Summer Time) is the local time a country adopts for a portion of the year, usually an hour forward from its standard official time.
It is a system intended to “save” daylight (as opposed to wasting it by, say, sleeping while the sun shines). The official time is adjusted forward during the spring and summer months, so that the active hours of work and school will better match the hours of daylight.
Locations that observe or do not observe DST are listed in the article Time_zone#List_of_time_zones_and_contained_areas.
It is sometimes asserted that DST was first proposed by Benjamin_Franklin in a letter to the editors of the Journal of Paris 1. However, the article was humorous; Franklin was not proposing DST, but rather that people should get up and go to bed earlier.
It was first seriously proposed by William_Willett in the “Waste of Daylight” 2, published in 1907, but he was unable to get the Parliament_of_the_United_Kingdom to adopt it despite considerable lobbying.
Canadian railroad engineer Sir Sandford_Fleming invented and proposed Standard_Time, which first divided the world into one-hour time zones, in 1878. It was not widely adopted by the railways until 1883, and even then it was not supported by any governmental body. However, it relieved the problem of scheduling train stops at separate stations set to their own time based on the local positioning of the sun, and it soon became widely accepted by railroads, freight clients, and passengers.
The idea of daylight saving time was first put into practice by the Germany government during the First_World_War between April_30, 1916 and October_1, 1916. Shortly afterwards, the United_Kingdom followed suit, first adopting DST between the May_21, 1916 and the 1st of October, 1916. Then on March_19, 1918 the United_States_Congress established several Time_zone (which were already in use by Railroad since 1883) and made daylight saving time official (which went into effect on 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so unpopular (mostly because people rose earlier and went to bed earlier than in modern times) that the law was later repealed.
Daylight saving time was reinstated in the United_States on February_9, 1942, again as a wartime measure to conserve resources, this time in order to fight World_War_II. This remained in effect until the war began winding down and the requirement was removed on September_30, 1945. From 1945 to 1966, there was no federal law about daylight saving time. States and localities were free to observe daylight saving time or not. The Uniform Time Act of 1966 mandated that daylight saving time begin nationwide on the last Sunday of April and end on the last Sunday of October. Any state that wanted to be exempt from daylight saving time could do so by passing a state law, provided that it exempts 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. The law was amended again in 1986 to begin daylight saving time on the first Sunday in April.
Criticism of DST
DST is not universally accepted; many localities do not observe it. Nevertheless, proponents claim that DST helps more than it hurts. The primary claim is that it reduces energy consumption. Opponents claim that there’s not enough benefit to justify needing to adjust clocks twice per year. The disruption in sleep patterns associated with setting clocks forward, and thereby “losing” an hour, correlates with a spike in the number of severe auto accidents, as well as emotional trauma.
Campaigners in United_Kingdom would like the country to stay on British_Summer_Time (BST) all year round, or in other words, adopt Central_European_Time and abolish BST. Alternatively, some would like Britain to adopt Central European Time and jump forward another hour during the summer (adopting a Single/Double Summer Time from Britain’s perspective). This would make winter evenings longer, thereby reducing traffic accidents and cases of Seasonal_affective_disorder. Opponents point to the longer hours of darkness on winter mornings, especially in Scotland, which might well cause an increase in road accidents. It has even been suggested that Scotland should be placed on a different Time_zone from the rest of the UK, which does not seem likely to occur in the foreseeable future.
DST is particularly unpopular among people working in Agriculture because the animals do not observe it, and thus the people are placed out of synchronization with the rest of the community, including school times, broadcast schedules, and the like.
DST is a long-standing controversy in Indiana, not only as an agricultural state, but also because the meridian separating the eastern and central Time_zone divides the state. In the past, neighboring communities sometimes ended up one or even two hours apart. In the current compromise, the state has three kinds of time zones: 77 counties, most of the state, are on Eastern Standard Time but do not use DST; 5 counties near Chicago and 5 counties in the southwestern corner of the state are on Central Standard Time and do use DST; and 2 counties near Cincinnati%2C_Ohio and 3 counties near Louisville%2C_Kentucky are on Eastern Standard time but do use DST.
DST around the world
For fairly obvious reasons, DST is a Temperate zone practice: day lengths in the Tropics do not vary enough to justify DST. Hawaii, the only U.S. state in the tropics, does not observe DST. However, Mexico has adopted DST nationwide, even in its tropical regions, because of its increasing economic ties to the U.S. The Mexican state of Sonora does not observe DST because it borders on a U.S. state that also does not observe DST (Arizona).
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, but it commonly begins in the Northern Hemisphere at 2:00 AM on either the first Sunday in April or the last Sunday in March, and ends at 2:00 AM on the last Sunday in October. In the Southern Hemisphere, the beginning and ending dates are switched (thus the time difference between e.g. the UK and Chile may be 3, 4 or 5 hours).
North_America generally follows the same procedure, going by local time in each zone, each time zone switching at 2am LST (local standard time) to 3am LDT on the first Sunday in April, and again from 2am LDT to 1am LST on the last Sunday in October.
All countries in Europe, except Iceland, observe DST and switch at the same universal time (1:00 UTC) in all five zones, going from 10pm/0/1/2/3am LST to 11pm/1/2/3/4am LDT simultaneously on the last Sunday in March, and back from 11pm/1/2/3/4am LDT to 10pm/0/1/2/3am LST on the last Sunday in October (formerly September), like in the USA (for the European Union, except the overseas territories, per EU directive 2000/84/EC 3; for Greenland: the Saturday before)).
Australia has had mixed implementation of Daylight Savings. Normally divided into three time zones, during Daylight Savings there are five distinct time zones ranging from UTC+8 to UTC+11. Despite several Referendum on the topic, Western_Australia, the Northern_Territory and Queensland still refuse to adopt the practice.
Cuba always starts on April 1 however, but keeps the same ending date.
The expression daylight savings time (with the extra “s”) is a common alternate form, but considered a usage error by some.
The Mnemonic “spring forward, fall back” tells us how to reset clocks when the time changes, regardless of hemisphere. (This uses the word “fall” to mean “Autumn”; while this usage has died out in British_English, it is still very common in American_English.)
Fire safety officials in 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. Most Smoke_detector are equipped with a “test” button for this purpose, or alternatively artificial smoke can be purchased, and has the advantage that it will also test the detector itself.
- EU directive 2000/84/EC
- Straightforward, good-looking discussion of DST, suitable for anybody of about age ten or over
- Daylight saving time, its history and why we use it
- DST changeover times throughout the world
- http://www.merlyn.demon.co.uk/uksumtim.htm – with future changeover dates EU (until 2007 final, from then extrapolating)
- World Time Server
- Time Zone Converter
- Sleep deficit and accidents
- Daylight saving humor
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