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; several ancient cultures lengthened each summer daylight hour instead. Modern DST was first proposed in 1907 by William Willett, and saw its first widespread use in 1916 as a wartime measure aimed at conserving coal. Despite controversy, many countries have used it since then; details vary by location and change occasionally.