What is the name of the system in which clocks are set ahead an hour every spring?

The system in which clocks are set ahead an hour every spring is Daylight Saving Time. It shifts an hour of daylight from the morning to the evening during part of the year.

The familiar phrase “spring forward, fall back” describes the two clock changes: clocks move ahead when daylight saving begins and return to standard time later in the year. The exact dates vary by country and region, and many places do not change their clocks at all.

The idea is often associated with Benjamin Franklin, who mentioned it humorously in 1784, but modern daylight-saving proposals were developed later. Germany became the first country to adopt it nationally in 1916 during World War I, partly to conserve fuel and extend useful evening light.

“Daylight Saving Time” is the standard American term; “summer time” is common in many other countries. The spelling “Daylight Savings Time” is widespread in everyday speech, but the official name is singular: Daylight Saving Time. The change can affect sleep, travel, broadcasts, and computer systems.