Daylight Saving Time (DST)
The practice of advancing clocks during summer months to extend evening daylight.
Daylight Saving Time (DST) is the practice of advancing clocks (typically by one hour) during summer months to extend evening daylight and reduce artificial light usage. The exact dates for DST transitions vary by country and region.
The modern concept of DST was first proposed by George Vernon Hudson in 1895 and was first implemented during World War I as a way to conserve coal. Today, about 40% of countries worldwide use DST, with notable exceptions including most of Africa and Asia.
DST transitions can cause various complications: - In spring, clocks "spring forward" (e.g., from 2:00 AM to 3:00 AM), resulting in one hour being skipped - In fall, clocks "fall back" (e.g., from 2:00 AM to 1:00 AM), resulting in one hour occurring twice
These transitions create challenges for scheduling, sleep patterns, and computer systems. In computing, handling DST correctly requires awareness of the specific rules for each time zone, which can change due to policy decisions.
The effectiveness and necessity of DST have been debated, with critics pointing to disruptions in sleep patterns, potential health impacts, and the complexity it adds to timekeeping systems. Some regions have moved to abolish the practice in favor of maintaining a consistent time year-round.