New Zealander George Hudson proposed the idea of daylight saving in 1895. Germany and Austria-Hungary organized the first nationwide implementation, starting on April 30, 1916. Many countries have used it at various times since then, particularly since the energy crisis of the 1970s.
Daylight saving time (DST) or summer time is the practice of advancing clocks during summer months by one hour so that evening daylight lasts an hour longer, while sacrificing normal sunrise times. Typically, regions with summer time adjust clocks forward one hour close to the start of spring and adjust them backward in the autumn to standard time.
Starting on April 30, 1916, Germany and its World War I ally Austria-Hungary were the first to use DST (German: Sommerzeit) as a way to conserve coal during wartime. Britain, most of its allies, and many European neutrals soon followed suit. Russia and a few other countries waited until the next year and the United States adopted it in 1918.
Broadly speaking, Daylight Saving Time was abandoned in the years after the war (with some notable exceptions including Canada, the UK, France, and Ireland for example). However, it was brought back for periods of time in many different places during the following decades, and commonly during the Second World War. It became widely adopted, particularly in North America and Europe starting in the 1970s as a result of the 1970s energy crisis.
In 2021 Daylight saving time (autumn) in USA falls on October 31.