Daylight Saving Time, also called summer time, system for uniformly advancing clocks, so as to extend daylight hours during conventional waking time in the summer months. In countries in the Northern Hemisphere, clocks are usually set ahead one hour in late March or in April and are set back one hour in late September or in October. The practice was first suggested in a whimsical essay by Benjamin Franklin in 1784. In 1907 an Englishman, William Willett, campaigned for setting the clock ahead by 80 minutes in four moves of 20 minutes each during April and the reverse in September.