||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. Despite controversy, many countries have used it since then; details vary by location and change occasionally.
Adding daylight to afternoons generally benefits retailing, sports, and other activities that exploit sunlight after working hours, ut it can cause problems for farmers and others whose hours depend on the sun. Extra afternoon daylight appears to cut traffic fatalities; its effect on health and crime is less clear. An early goal was to reduce evening usage of incandescent lighting, formerly a primary use of electricity; nowadays, though, DST sometimes increases overall electricity costs and peak demand.