Daylight saving time

Daylight saving time (DST), also referred to as daylight saving(s), daylight savings time, daylight time (United States and Canada), or summer time (United Kingdom, European Union, and others), is the practice of advancing clocks to make better use of the longer daylight available during summer so that darkness falls at a later clock time. The typical implementation of DST is to set clocks forward by one hour in spring or late winter, and to set clocks back by one hour to standard time in the autumn (or ''fall'' in North American English, hence the mnemonic: "spring forward and fall back").

DST is not usually observed near the Equator, where sunrise and sunset times do not vary enough to justify it; conversely, it is often not observed in places at high latitudes where a one-hour clock shift would provide little benefit because of the wide variations in sunrise and sunset times. Consequently, only a minority of the world's population uses DST. Some countries observe it only in some regions for example: it is observed only by some Australian states and by all states in the United States except for Hawaii and Arizona (within the latter, however, the Navajo Nation does observe it.

Historically, several ancient societies adopted seasonal changes to their timekeeping to make better use of daylight; Roman timekeeping even included changes to water clocks to accommodate this. However, these were changes to the time divisions of the day rather than setting the whole clock forward. In a satirical letter to the editor of the ''Journal de Paris'' in 1784, Benjamin Franklin suggested that if Parisians could only wake up earlier in the summer they would economize on candle and oil usage, but he did not propose changing the clocks. In 1895, New Zealand entomologist and astronomer George Hudson made the first realistic proposal to change clocks by two hours every spring to the Wellington Philosophical Society, but this was not implemented until 1928 and in another form. In 1907, William Willett proposed the adoption of British Summer Time as a way to save energy but although seriously considered by Parliament it was not implemented until 1916.

The first implementation of DST was by Port Arthur (today merged into Thunder Bay), in Ontario, Canada, in 1908, but only locally, not nationally. The first nation-wide implementations were by the German and Austro-Hungarian Empires, both starting on 30 April 1916. Since then, many countries have adopted DST at various times, particularly since the 1970s energy crisis. Provided by Wikipedia