daylight saving time

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daylight saving time

(DST), time observed when clocks and other timepieces are set ahead so that the sun will rise and set later in the day as measured by civil timecivil time,
local time based on universal time. Civil time may be formally defined as mean solar time plus 12 hr; the civil day begins at midnight, while the mean solar day begins at noon.
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. The amount of daylight on a given dayday,
period of time for the earth to rotate once on its axis. The ordinary day, or solar day, is measured relative to the sun, being the time between successive passages of the sun over a stationary observer's celestial meridian.
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 of the year at a given latitude is fixed, but over the year the hours of sunrise and sunset vary from day to day. During the summer months, the sun rises earlier and sets later and there are more hours of daylight. If clocks and other timepieces are set ahead in the spring by some amount (usually one hour), the sun will rise and set later in the day as measured by those clocks. This provides more usable hours of daylight for activities that occur in the afternoon and evening, such as outdoor recreation. Daylight saving time can also be a means of conserving electrical and other forms of energy. In the fall, as the period of daylight grows shorter, clocks are set back to correspond to standard timestandard time,
civil time used within a given time zone. The earth is divided into 24 time zones, each of which is about 15° of longitude wide and corresponds to one hour of time. Within a zone all civil clocks are set to the same local solar time.
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Benjamin Franklin, when serving as U.S. minister to France, wrote an article recommending earlier opening and closing of shops to save the cost of lighting. In England, William Willett in 1907 began to urge the adoption of daylight saving time. During World War I the plan was adopted in England, Germany, France, and many other countries. In the United States, Robert Garland of Pittsburgh was a leading influence in securing the introduction and passage of a law (signed by President Wilson on Mar. 31, 1918) establishing daylight saving time in the United States. After World War I the law was repealed (1919). In World War II, however, national daylight saving time was reestablished by law on a year-round basis. National year-round daylight saving time was adopted as a fuel-saving measure during the energy crisis of the winter of 1973–74. In late 1974, standard time was reinstituted for the winter period. In 1987 federal legislation fixed the period of daylight saving time in the United States as the first Sunday (previously the last Sunday) in April to the last Sunday in October; it was expanded in 2005 (effective 2007) to extend from the second Sunday in March to the first Sunday in November. Arizona and Hawaii do not use daylight saving time.

daylight saving time

[¦dā‚līt ‚sāv·iŋ ‚tīm]
(astronomy)
A variation of zone time, usually 1 hour more advanced than standard time, frequently kept during the summer to make better use of daylight. Also known as summer time.
References in periodicals archive ?
Supervisor Zev Yaroslavsky, who cast the dissenting vote, said he's glad daylight-saving time ends this weekend.
Heck, we can stay up all night burning energy galore and still lick that guy with our National Guard, so daylight-saving time can't be tied to helping the war effort anymore.
31, 2014 /PRNewswire/ -- Getting an extra hour of sleep this weekend is not a dream to most area residents, as four in 10 New Englanders said they'll sleep in and take advantage of the "extra" hour granted by the end of daylight-saving time, according to a survey conducted this week by local furniture and bedding retailer Bernie & Phyl's.
Just ask the folks who woke up Sunday morning feeling they ought to set their clocks back -- only to be reminded by a friend, neighbor or the media that daylight-saving time was being extended one week beginning this year.
An ideal study of daylight-saving time would randomly allocate time schemes across regions, a difficult experiment to execute.
Typically, daylight-saving time began on the first Sunday in April and ended on the last Sunday in October.
During the past several months companies such as Microsoft and Apple have created software patches to tell computers daylight-saving time starts on the second Sunday in March instead of the first Sunday in April and ends on the first Sunday in November instead of the last Sunday in October.
In many cases, making the necessary changes to accommodate the new daylight-saving time schedule will be relatively minor.
A conference committee has scaled back a plan to extend daylight-saving time after several business groups protested the change.
To make the most of the time in bed, we recommend that older people go to bed early to pay back their debt or to make up for the hour on daylight-saving time.
The initiative to designate the three time zones, which was easily approved in the energy committee, also proposed the use of daylight-saving time from the beginning of April to the end of October.
About two years would be needed to familiarize people with daylight-saving time and for the government to prepare, the report said.