National GeographicWhen do we switch to daylight saving time this year? In 2026, daylight saving time will take effect on March 29 and end on October 25. On the last Sunday of March at 2:00 a.m., clocks move forward one hour, causing us to lose an hour of sleep. Daylight saving time ends on the last Sunday of October at 2:00 a.m. We then turn the clocks back one hour and gain an hour of sleep. Why does the length of daylight vary? The seasonal changes in daylight hours are due to the tilt of the Earth's axis. Our planet spins on its axis at a relatively constant angle of about 23.4 degrees relative to the vertical of the plane of its orbit around the Sun. Thus, at the equator day and night last about twelve hours each, year-round. But that does not hold true when you move toward the south or toward the north. For the Northern Hemisphere, summer is synonymous with sun. It is the time when this part of the globe is tilted toward the Sun and days are longer and warmer. Meanwhile, the Southern Hemisphere experiences the shorter days of winter, because it tilts to the other side. Six months later, the situation reverses, and winter takes hold of the North while the South basks in the light. When coal was burned to produce the electricity that powered lamps, daylight saving time was introduced to add an extra hour of daylight at the end of each workday by advancing or delaying by an hour to align with daylight. As a result, whether a region participates partly depends on its distance from the equator. In countries farthest from it, the difference in day length between summer and winter is more pronounced; these countries are more likely to participate in the daylight-saving system. Why was daylight saving time created? Many attribute the invention of daylight saving time to Benjamin Franklin on the basis of a letter that was probably satirical he sent to the Journal de Paris in 1784. In it, he expressed astonishment at seeing the sun rise at the improper hour of six in the morning, long before most Parisians see daylight themselves. If they rose with the sun, he wrote, the city could save an “immense sum” on candles burned during the evening hours of darkness. However, he never suggested moving clocks forward or backward but proposed other playful solutions to the problem: firing cannons in the streets to wake residents, taxing the use of shutters, and restricting the sale of candles. Others attribute the paternity of the idea to George Hudson, a New Zealand entomologist who, in 1895, proposed a two-hour shift so he could go insect-hunting after work. Soon after, a British activist named William Willett proposed a similar idea to prevent waste of daylight and presented it to the British Parliament early in the 20th century. It was only when resources dwindled during World War I that Germany decided to adopt the time change. In 1916, the country implemented daylight saving time to maximize the use of resources during sunny hours, a first. The United Kingdom followed suit in the same year, and France and the United States followed suit by implementing seasonal time changes in 1917 and 1918, respectively. Who observes the switch to daylight saving time? Not everyone participates in these cascading time changes. In the United States, nineteen states have legislated or adopted resolutions to remain on daylight saving time permanently, but those laws would take effect only if Congress passes the Sunshine Protection Act. In the meantime, a few states and territories have already decided to simply abandon daylight saving time: Hawaii, Arizona (except the Navajo Nation) and the territories of Guam, Puerto Rico, American Samoa, the U.S. Virgin Islands, and the Northern Mariana Islands. In the rest of the world, the popularity of daylight saving time varies as well. Most of North America, Europe, New Zealand, and some regions of the Middle East observe this annual change, though each has its own start and end dates. But the majority of African and Asian countries neither move their clocks forward nor backward. South America and Australia are, in turn, split on the issue. However, EU participation could soon change. In 2019, the European Union voted to end the mandatory daylight saving change, which runs from March to October. But that plan currently appears on hold: Brexit and the Covid-19 pandemic have stalled talks within the EU. Does daylight saving time bring benefits? For many, the time change is a form of interference and leads to many failed meetings and episodes of fatigue. It may even have more serious effects. Some studies have identified a rise in heart attacks coinciding with advancing by one hour and a slight decrease coinciding with the moment when one hour is set back. Other studies suggest that the time change could be correlated with an increase in deadly car accidents, even if the effect is small compared with the total number of accidents each year. There is also concern that the inevitable loss of sleep could affect the immune system. Furthermore, many studies question whether there has ever been any energy savings at all. In 2008, a study from the U.S. Department of Energy suggested that in the United States, four additional weeks spent on daylight saving time would save about 0.5% of the total electricity used in a day. And others conclude that it simply comes down to the same thing: later daylight hours do indeed lower electricity consumption at that time, but they also drive up air conditioning use in the evening or increase energy demand in the morning when it is still dark. Nevertheless, these effects may depend on where in the world you are. According to one study, daylight saving time would lead to higher energy demand and pollution emissions in Indiana, while another finds that daylight saving time leads to slight decreases in energy consumption in Norway and Sweden. These days, the arguments in favor of daylight saving time generally revolve around the stimulating effect this time change has on evening activities. We tend to stay outdoors when it is still light after work (playing sports, going for a walk, taking the kids out to play) rather than sitting on the couch. Many outdoor sectors such as golf or barbecuing are indeed supporters of daylight saving time, because they say it increases their profits. The oil industry is a strong proponent, as more people hit the road if it is still light after work or after school. But in many places, the time change is particularly unpopular. The European Union’s push to abandon this seasonal change comes from a series of polls showing that nearly 80% of respondents were against the time change. In France, that figure rises to 83% of respondents. As for the choice of keeping daylight saving time or standard time, almost 60% of respondents said they would always prefer to stay on daylight saving time. This article originally appeared on nationalgeographic.com in English.
14 July, 2026
