Wednesday, October 30, 2013


Time is a dimension in which events can be ordered from the past through the present into the future, and also the measure of durations of events and the intervals between them. Time has long been a major subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems. Some simple, relatively uncontroversial definitions of time include "time is what clocks measure" and "time is what keeps everything from happening at once".

Daylight saving time
Daylight saving time (DST) -also summer time in British English and zomertijd in Dutch - is the practice of advancing clocks during the lighter months so that evenings 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.

The modern idea of daylight saving was first proposed in 1895 by George Vernon Hudson and it was first implemented by Germany and Austria-Hungary starting on 30 April 1916. Many countries have used it at various times since then. Much of the United States used DST in the 1950s and 1960s, and DST use expanded following the 1970s energy crisis. It has been widely used in North America and Europe since then.

The practice has been both praised and criticized. Adding daylight to evenings benefits retailing, sports, and other activities that exploit sunlight after working hours, but can cause problems for evening entertainment and other occupations tied to the sun (such as farming) or to darkness (such as drive-in theatres). Although an early goal of DST was to reduce evening use of incandescent lighting (formerly a primary use of electricity, modern heating and cooling usage patterns differ greatly, and research about how DST currently affects energy use is limited or contradictory.

DST clock shifts present other challenges. They complicate timekeeping, and can disrupt meetings, travel, billing, record keeping, medical devices, heavy equipment, and sleep patterns. Software can often adjust computer clocks automatically, but this can be limited and error-prone, particularly when DST dates are changed.

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