daylightsaving

Daylight saving time (DST) is the practice of setting clocks forward by one hour during part of the year to extend evening daylight, and then returning to standard time in autumn. The change is typically intended to shift daylight toward later in the day, reducing artificial lighting use and encouraging evening activity.

The idea has historical roots in the 18th century with Benjamin Franklin’s observations on candles and daylight use, but the modern system was proposed in the early 20th century by William Willett. DST was first widely adopted during World War I and has since been introduced, modified, or repealed in many countries. Today, DST is observed in parts of Europe, North America, and other regions, but it is not universal. Regions near the equator generally do not observe DST because daylight patterns remain relatively constant year-round.

How DST is applied varies by jurisdiction. In the United States, clocks typically move forward one hour on the second Sunday in March and move back on the first Sunday in November. In the European Union, changes usually occur on the last Sunday in March and the last Sunday in October. Other countries may have different dates, or may discontinue DST entirely, opting for permanent standard time or permanent daylight saving.

Pros and cons of DST are debated. Proponents argue that extra evening daylight supports outdoor activity and can reduce energy use, while critics point to disrupted sleep, health effects, and questionable energy savings. The continued use and future of DST remain subjects of policy discussion in many regions.