The United Kingdom will set clocks back by one hour at 2 a.m. on Sunday, marking the end of British Summer Time and a return to Greenwich Mean Time. While this annual adjustment offers an extra hour of sleep, experts caution that the change may disrupt the body’s internal clock and have broader health implications.

The practice of shifting clocks forward and backward, known as daylight saving time, dates back more than a century. Its origins include New Zealand post office worker George Hudson, who in 1895 proposed shifting clocks to gain more evening daylight for collecting insects. In the UK, Kent builder William Willett championed the idea after observing that many window blinds were still drawn early in the morning. Willett published a pamphlet, *The Waste of Daylight*, and campaigned for the introduction of daylight saving until his death in 1915. The concept was officially adopted in Britain in 1916 amid World War I, following similar moves by Germany.

Over the decades, Britain’s practice has evolved. During World War II, the country remained two hours ahead in summer, while a trial from 1968 to 1971 tested staying on GMT+1 year-round. That experiment ended largely due to complaints about dark mornings, especially in Scotland. Since 2002, the UK has aligned with EU directives, advancing clocks on the last Sunday in March and reverting on the last Sunday in October.

Despite its long history, some scientists now question the overall benefits of the time change. Dr. Ramona von Leden, a neuroscientist specializing in circadian rhythms, argues the original justification—that farmers and others need the extra daylight—is outdated. She explains that the one-hour shift can negatively affect the suprachiasmatic nucleus, the brain’s internal clock regulator, causing disruption to the body’s natural 24-hour cycle.

“When it’s dark, our body naturally starts to wind down and prepare for sleep, but our modern schedules often conflict with this rhythm,” Dr. von Leden said. She notes that the time shift requires the brain to reset, which can take several days, and this misalignment may affect mood and well-being. She also emphasized reduced sunlight exposure during winter months can lead to lower vitamin D levels, contributing to seasonal affective disorder, a form of depression.

To help ease the adjustment, Dr. von Leden recommends seeking natural daylight whenever possible and using red-light therapy. She advises treating exposure to daylight as a fixed appointment to support the body’s adaptation.

This year’s change will provide an extra hour of rest as clocks move back to 1 a.m. local time on Sunday, but it also signals the onset of darker evenings and the gradual approach of winter, posing challenges to maintaining regular sleep and activity patterns. Clocks will advance again on March 28, 2027.