Spring forward, fall back: In spring, clocks move forward by 1 hour — you lose an hour of sleep but gain an hour of evening daylight. In autumn, clocks move back by 1 hour — you gain an hour of sleep but lose evening light.
Why do we have daylight saving time?
Daylight saving time was introduced during World War I as a measure to conserve energy — by shifting daylight to evening hours, countries hoped to reduce the use of artificial lighting. Germany was the first country to introduce it in 1916, and most of Europe and North America followed shortly after.
The original energy-saving argument has since been largely debunked. Modern research shows that DST often increases energy consumption in warmer climates because of increased air conditioning use in warmer evenings. The main benefit today is simply more daylight in the evenings during summer months.
Health effects of changing clocks
The spring clock change is consistently associated with negative health effects. Studies show a 24% increase in heart attacks in the days following the spring change, along with increased rates of strokes, traffic accidents and workplace injuries. The disruption to sleep is the primary cause — even losing 1 hour of sleep has measurable effects on the body.
The autumn change (gaining an hour) has milder effects but is also associated with increased depression rates as evenings get darker earlier.
Will the US and EU abolish DST?
The EU voted to end seasonal clock changes in 2019, but implementation has been repeatedly delayed as member states cannot agree on whether to permanently adopt summer time (UTC+1/2) or winter time (UTC+0/1). As of 2025 Europeans still change their clocks twice a year.
In the US, the Sunshine Protection Act — which would make daylight saving time permanent — passed the Senate unanimously in 2022 but stalled in the House. Americans still change clocks twice per year.