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Daylight saving time 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; the ancients lengthened summer hours instead. Presaged by a 1784 satire, modern DST was first proposed in 1907 by William Willett, and 1916 saw its first widespread use as a wartime measure aimed at conserving coal. Despite controversy, many countries have used it since then; details vary by location and change occasionally. Adding daylight to afternoons benefits retailing, sports, and other activities that exploit sunlight after working hours, but causes problems for farmers and other workers whose hours depend on the sun. Extra afternoon daylight cuts traffic fatalities; its effect on health and crime is less clear. DST is said to save electricity by reducing the need for artificial evening lighting, but the evidence for this is weak and DST can boomerang by boosting peak demand, increasing overall electricity costs. DST's clock shifts complicate timekeeping and can disrupt meetings, travel, billing, medical devices, and heavy equipment.