Daylight saving time is not necessary in any strict sense. The energy savings it was designed to produce are negligible by modern estimates, and the health and safety costs of switching clocks twice a year are well documented. Most of the world’s countries don’t observe it, and a growing number have abandoned it in recent years. The real debate now isn’t whether we need the time change, but what we’d replace it with.
The Energy Argument Has Largely Collapsed
The original pitch for daylight saving time was simple: shift an hour of daylight to the evening, and people use less electricity for lighting. That logic made sense in a world where lighting was the dominant household energy cost. It makes far less sense now.
The most widely cited early study, a 1975 report from the U.S. Department of Transportation, found roughly a 1% reduction in electricity load during transition periods. But a follow-up evaluation by the National Bureau of Standards concluded those savings were “questionable and statistically insignificant.” A California Energy Commission simulation found DST left electricity consumption virtually unchanged from May through September and reduced it by only 0.15% to 0.3% in April and October. When the Department of Energy studied the 2007 DST extensions (which added several weeks to the schedule), it estimated savings of about 0.5% per day of extended DST. That’s real, but tiny.
One influential study from Indiana told an even less flattering story. When the state adopted DST statewide in 2006, researchers at Yale could directly compare energy use before and after. They found that while lighting costs dropped slightly, air conditioning use in the evenings and heating use in the mornings more than offset those gains. In a modern economy where climate control dominates energy bills, the old lighting argument barely registers.
The Health Costs Are Measurable
Losing an hour of sleep in March isn’t just annoying. The spring transition is associated with a 10% to 24% increase in heart attack risk on the following Monday and, to a lesser extent, Tuesday. That spike lines up with what sleep researchers would predict: even a one-hour shift disrupts circadian rhythms, raises stress hormones, and strains the cardiovascular system in people already at risk.
The mechanism is straightforward. Your internal clock is set primarily by morning light exposure. During daylight saving time, from March through November, your body gets less morning light and more evening light. That mismatch can leave you feeling tired in the morning and alert at night, a pattern that compounds over days and weeks. Poor sleep from this disruption can also worsen depression, anxiety, and seasonal affective disorder.
These aren’t effects that fade quickly. While most people adjust within a few days, studies on circadian biology suggest the body’s deeper rhythms can take weeks to fully realign. For people with existing sleep disorders or mental health conditions, the transition can be a genuine setback.
Roads Get More Dangerous in Spring
A study of fatal crashes across the contiguous United States from 2010 to 2019 found that motor vehicle occupant fatalities increased by 12% in the five weeks after the spring time change. The fall change showed the opposite pattern: a 7.1% decrease in fatal crashes among vehicle occupants.
The picture gets more nuanced when you include pedestrians and cyclists. The spring shift, by pushing more daylight into the evening, actually reduced pedestrian and cyclist fatalities (fewer people walking in the dark after work). The fall shift reversed that benefit. Across both transitions, the net result was roughly a wash: 26 fewer pedestrian and cyclist deaths balanced against 29 additional motor vehicle occupant deaths. The clock changes don’t save lives on the road. They redistribute which lives are at risk.
Evening Light Does Reduce Crime
One area where DST shows a clear benefit is crime reduction. A Stanford analysis found that robbery rates dropped by an average of 51% during the hour around sunset following the spring shift. Robberies are heavily concentrated in the early evening, and an extra hour of daylight removes the cover of darkness that many street crimes depend on. This is a significant effect, and it’s one of the strongest arguments for keeping clocks shifted forward.
Consumer Spending Shifts With the Light
People spend more money when they have more evening daylight. A JPMorgan Chase Institute report found that consumer spending dropped 3.5% at grocery stores, gas stations, and retailers in the month after clocks fell back in autumn. In Los Angeles, the effects were even sharper: spending fell 4.8% at retail stores and 5.9% at grocery stores. The pattern is intuitive. When it’s dark by 5 p.m., people go straight home. When sunset is at 7 or 8, they stop at stores, eat out, and run errands. Industries like golf and outdoor recreation have historically lobbied hard to keep DST for exactly this reason.
Farmers Never Wanted It
One of the most persistent myths about daylight saving time is that it was created for farmers. The opposite is true. Farmers have long opposed the time change because their schedules are dictated by the sun and by their animals, not by clocks. Cows need milking at the same solar time regardless of what the clock says, and dew on crops doesn’t evaporate an hour earlier just because Congress said so. The farming lobby actively fought DST when it was first introduced during World War I and again when it was standardized in the 1960s.
Most of the World Has Moved On
Fewer than 70 countries observe daylight saving time today. Several large nations have recently abandoned it. Brazil dropped DST in 2020, Turkey in 2018, and Argentina in 2009. Russia tried permanent summer time in 2011, citing research that clock changes caused “stress and illness,” then switched to permanent winter (standard) time in 2014 after citizens complained about dark mornings. China, with 1.4 billion people, stopped observing DST back in 1991. South Korea dropped it the same decade.
Russia’s experience is particularly instructive. When the country locked clocks into permanent summer time, sunrise in Moscow during winter didn’t arrive until nearly 10 a.m. The mismatch between clock time and solar time was so disorienting that Russia reversed course three years later, choosing permanent standard time instead. Sleep scientists in the U.S. and Europe have pointed to Russia’s experiment as evidence that permanent daylight saving time, while popular in concept, creates real problems in practice.
Where U.S. Legislation Stands
The U.S. Senate unanimously passed the Sunshine Protection Act in 2022, which would have made daylight saving time permanent year-round. The bill died in the House. A new version, the Sunshine Protection Act of 2025, was introduced in January 2025 and referred to the House Committee on Energy and Commerce. It has not advanced further.
The sticking point isn’t whether to stop changing clocks. Polls consistently show that most Americans want to pick one time and stay there. The disagreement is over which time. Sleep researchers and medical organizations overwhelmingly favor permanent standard time, arguing that it better aligns civil time with the solar cycle and preserves the morning light exposure that anchors healthy circadian rhythms. Proponents of permanent daylight saving time, including many in the retail and recreation industries, prefer the extra evening light and the economic activity it generates.
Under current federal law, states can opt out of DST and stay on standard time year-round (Hawaii and most of Arizona already do), but they cannot adopt permanent daylight saving time without congressional approval. More than a dozen state legislatures have passed bills signaling their intent to move to permanent DST if Congress allows it.
What “Necessary” Really Means Here
The twice-yearly time change produces no meaningful energy savings, raises heart attack and traffic fatality risks every spring, disrupts sleep for weeks, and exists largely because of legislative inertia. Its genuine benefits, reduced evening crime and higher consumer spending, are arguments for more evening daylight, not for switching clocks twice a year. Those benefits could be preserved by choosing permanent daylight saving time and staying there, though that choice comes with its own tradeoff: darker winter mornings that work against your body’s natural rhythms. Permanent standard time avoids that problem but sacrifices the summer evening light most people enjoy.
The one thing nearly every researcher, legislator, and affected industry agrees on is that the switching itself is the worst option. The clock change combines the downsides of both systems while adding a biannual disruption that measurably harms public health and safety.