British Summer Time (BST)

British Summer Time (BST) - UK Daylight Saving Time
When is British Summer Time (BST) in force this year?
2008: Sunday 30 March 01:00 GMT - Sunday 26 October 01:00 GMT (02:00 BST)
Also :
IST = Irish Summer Time (Ireland), WEDT = Western European Daylight Time, WEST Western European Summer Time
(From: BritishSummerTime.co.uk)
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Daylight Saving Time
(This article is about DST in general).
Daylight saving time (DST; also summer time in British English) is the convention of advancing clocks so that afternoons have more daylight and mornings have less. Typically clocks are adjusted forward one hour near the start of spring and are adjusted backward in autumn. Modern DST was first proposed in 1907 by William Willett. Many countries have used it since then; details vary by location and change occasionally.
The practice is controversial. Adding daylight to afternoons benefits retailing, sports, and other activities that exploit sunlight after working hours, but causes problems for farming, entertainment and other occupations tied to the sun. Extra afternoon daylight reduces traffic fatalities; its effect on health and crime is less clear. An early goal of DST was to reduce evening usage of incandescent lighting, formerly a primary use of electricity; modern heating and cooling usage patterns can cause DST to increase electricity consumption.
DST's clock shifts can serve as fire safety reminders, but they complicate timekeeping and can disrupt meetings, travel, billing, recordkeeping, medical devices, and heavy equipment. Many computer-based systems can adjust their clocks automatically, but this can be limited and error-prone, particularly when DST rules change.

Origin
William Willett invented DST and advocated it tirelessly. The prominent English builder and outdoorsman William Willett invented DST in 1905 during one of his pre-breakfast horseback rides, when he observed with dismay how many Londoners slept through the best part of a summer day. An avid golfer, he also disliked cutting short his round at dusk. His solution was to advance the clock during the summer months, a proposal he published two years later. He lobbied unsuccessfully for the proposal until his death in 1915; see Politics for more details.
Germany, its World War I allies, and their occupied zones were the first European nations to use Willett's invention, starting April 30, 1916. Britain, most of its allies, and many European neutrals soon followed suit; Russia and a few other countries waited until the next year; and the United States adopted it in 1918. Since then, the world has seen many enactments, adjustments, and repeals.

Energy use
Delaying the nominal time of sunset and sunrise reduces the use of artificial light in the evening and increases it in the morning. As Franklin's 1784 satire pointed out, lighting costs are reduced if the evening reduction outweighs the morning increase, as in high-latitude summer when most people wake up well after sunrise. An early goal of DST was to reduce evening usage of incandescent lighting, formerly a primary use of electricity. Although energy conservation remains an important goal, studies are contradictory, and suggest that DST can increase energy use in some common cases:

Economic effects
Retailers, sporting goods makers, and other businesses benefit from extra afternoon sunlight, as it induces customers to shop and to participate in outdoor afternoon sports.
(From Wikipedia, the free encyclopedia)