The case against daylight saving time has grown substantially stronger in recent years, backed by mounting evidence that the biannual clock change harms cardiovascular health, increases traffic fatalities, disrupts sleep on a population-wide scale, and fails to deliver the energy savings it was designed to produce. More than seven in ten Americans now prefer ending the practice altogether, and major medical organizations have formally called for its elimination.
The Spring Shift Strains Your Heart
Losing a single hour of sleep sounds trivial. But the Monday after clocks spring forward, the risk of having a heart attack jumps by 10 to 24 percent, with elevated risk continuing into Tuesday. That spike isn’t random. Sleep loss triggers stress hormones, raises blood pressure, and increases inflammation, all of which can destabilize vulnerable plaques in coronary arteries. For someone already at risk, that one lost hour can be the tipping point.
Strokes follow a similar pattern. Hospitalizations for ischemic stroke, the most common type, rise by about 8 percent in the first two days after the transition. The fall “gain” of an hour doesn’t produce a comparable protective effect. The damage from the spring shift is real and measurable, while the supposed benefit of “extra” sleep in autumn largely dissolves into disrupted routines and confused body clocks.
More Crashes, More Missed Appointments
A University of Colorado Boulder study found that fatal car crashes in the U.S. increase roughly 6 percent in the week following the spring time change. Drowsy driving is the primary culprit. Millions of people get behind the wheel on that Monday morning having slept poorly, with reflexes and attention measurably impaired. Unlike a bad night’s sleep that an individual might choose to compensate for, the time change hits an entire population simultaneously, flooding roads with underslept drivers all at once.
The disruption ripples into healthcare too. The spring transition is associated with more missed medical appointments and higher rates of emergency department and hospital return visits. The fall reversal doesn’t trigger the same problems, which tells researchers the issue isn’t just about gaining or losing an hour. It’s about the acute shock of forced schedule change conflicting with biology.
Your Body Clock Prefers Morning Light
The strongest scientific argument against daylight saving time comes from circadian biology. Your body runs on an internal clock that’s roughly 24 hours and 12 minutes long. Light is the primary signal that keeps this clock synchronized with the actual day. Morning light speeds the clock up to match a 24-hour cycle. Evening light slows it down, pushing it out of alignment.
This is why permanent standard time, not permanent daylight saving time, is what sleep scientists recommend. Standard time places sunrise earlier in the morning, giving your body the light signal it needs to stay properly synchronized. Daylight saving time does the opposite: it shifts light later into the evening and delays sunrise, weakening the circadian signal that keeps your sleep, immune system, metabolism, and energy levels running in coordination.
A 2025 Stanford Medicine study modeled the “circadian burden” of each time policy across the country, calculating how much a person’s internal clock has to strain to keep pace with the 24-hour day under different light conditions. They found that most Americans would experience the least circadian burden under permanent standard time. Their estimates suggest that adopting permanent standard time nationwide could mean roughly 300,000 fewer strokes and 2.6 million fewer people living with obesity, driven by improvements in circadian health that compound over years.
The Energy Argument Has Collapsed
Daylight saving time was originally justified as an energy conservation measure. The logic seemed straightforward: more evening daylight means fewer lights switched on. But decades of research have failed to confirm meaningful savings, and several studies show the opposite effect.
The most commonly cited early study, a 1975 Department of Transportation report, claimed about a 1 percent reduction in electricity use. A subsequent evaluation by the National Bureau of Standards concluded those savings were “questionable and statistically insignificant.” When the Department of Energy revisited the question in 2008 after Congress extended DST by several weeks, it found savings of just 0.5 percent on extended days.
Meanwhile, a rigorous natural experiment in Indiana, where some counties adopted DST for the first time, found that the policy actually increased residential electricity demand by about 1 percent. The reason: while lighting costs dropped slightly in the evenings, air conditioning use surged during the added hours of afternoon heat and sunlight. Heating costs rose in dark, cold mornings. Similar findings have emerged from engineering simulations and studies in Japan, all pointing to the same conclusion. Whatever tiny lighting savings DST once provided have been erased or reversed by modern heating and cooling patterns.
What Medical Organizations Recommend
The American Academy of Sleep Medicine has taken a clear position: the U.S. should adopt permanent standard time. Their statement calls current evidence strongly supportive of year-round standard time as the option that “aligns best with human circadian biology and provides distinct benefits for public health and safety.” The American Medical Association has echoed this position.
This is an important distinction, because most legislative proposals (including the Sunshine Protection Act that passed the U.S. Senate in 2022 before stalling) have pushed for permanent daylight saving time instead. That would mean later sunrises year-round. In northern states during winter, children would routinely head to school in complete darkness. A survey found that nearly two-thirds of parents (64 percent) said they would be concerned about their children’s safety under those conditions. Sleep scientists warn that permanent DST would lock in the very circadian misalignment that makes the current system harmful, turning a twice-yearly disruption into a chronic one.
The One Real Tradeoff
Daylight saving time does have one documented benefit worth acknowledging. A Stanford analysis of crime data found that robbery rates drop by an average of 51 percent during the sunset hour after clocks spring forward, because criminals who rely on darkness lose cover. More evening light genuinely does reduce certain types of street crime.
But this benefit applies to a narrow window of the day and a specific category of crime, while the health costs affect the entire population around the clock for days or weeks after each transition. And under permanent standard time, summer evenings would still have plenty of daylight. The tradeoff only becomes stark in winter months, when the choice is between a dark morning commute and a dark evening one. Circadian scientists argue that biology should win that debate: dark mornings carry a steeper health penalty because they deprive the body of the light signal it most needs.
Where Public Opinion Stands
A 2025 Gallup poll found that 54 percent of Americans want to stop changing clocks, up from around 20 percent opposition in the 1990s. When asked which system they’d prefer year-round, 48 percent chose permanent standard time, 24 percent chose permanent daylight saving time, and just 19 percent wanted to keep switching. That means the current system is the least popular option by a wide margin.
The gap between public desire and policy action comes down to a disagreement not about whether to stop changing clocks, but about which time to keep. Permanent DST appeals to people who picture long summer evenings. Permanent standard time appeals to scientists and anyone who has tried to wake a teenager for school in the dark. Until legislators and the public converge on the same answer, the clocks will likely keep changing, and so will the toll that comes with them.