Falling back: In defense of standard time
It’s that time of the year! No, not the holidays… Daylight savings time comes to an end soon - for Europeans 26 October, and for Americans next weekend on November 2. Yup, it’s time to “fall back” and we will all get an extra hour to sleep! As a night owl chronotype, it’s my favorite day of the year. Still, I would absolutely give up Fall Back day and get rid of daylight savings time, based on the science! Read on for why standard time is best for our health, and tips for the upcoming time change.
How Daylight Savings Time Harms Your Health
Our bodies run on an internal clock, called the circadian rhythm, which controls when we feel sleepy or alert, when hormones are released, our metabolism, and even how our immune system functions. The circadian rhythm is finely tuned to 24 hours, primarily by light and darkness.
When we “spring forward” or “fall back,” we are abruptly stressing our circadian rhythms, throwing a wrench in all those processes that rely on the 24-hour clock. Most obvious is our sleep: when we “fall back” we will go to bed an hour later, but our circadian rhythm will wake us up when it was set to, meaning we lose an hour of sleep. So the slight sleep deprivation piles on top of the many other disruptions to our body’s numerous functions. Most of us will seemingly shrug it off in a few days, but research shows that we are paying for DST with our health.
While an hour doesn’t sound like much, research shows that it takes a week or more for our bodies to adjust. For example, heart attacks and strokes are more common in the week after the time change, likely due to disruptions in circadian blood pressure regulation and hormone (such as cortisol) release. A recent paper from Stanford researchers(1) examined the health burden related to daylight savings time, and by their estimate, 300,000 (not a typo) strokes could be reduced per year in the US alone if we got rid of daylight savings time. This study, which modeled the prevalence of health problems county-by-county across each time zone, also showed that stopping daylight savings time would reduce obesity by 0.78%… which is 2.6 million people!
Fatal car accidents also increase in the week after time changes: a recent study(2) found there was a 12% increase in car accident deaths after the spring time change and actually a decrease in motor vehicle accident deaths in the autumn (-7%), however this is more than made up for increase in pedestrian and bicyclist deaths due to car crashes after the fall time change (13%). Overall, the pedestrian/bicyclist deaths appear more related to the amount of light, whereas the car accident deaths are more related to sleep loss.
Even if we avoid death by accident, and heart attacks and strokes, we still have some mental doldrums after the time change. One study of SAT scores found they tended to be lower after the time change. In working adults, decreased productivity lingers for about 2 weeks after the time change!
And then, there is just the general misery of the time change, which is especially acute for anyone with young children (or pets who expect to be fed on time). When my kids were little, it seemed they had only just settled into a good bedtime routine when the blasted time would change again!
Why do we have daylight savings anyway?
No, it’s not about the farmers! Initially, daylight savings started as an effort to save energy sources by having more sunlight available in the evenings, thereby reducing electricty/energy use. However, an analysis by the US Department of Energy showed that with our modern lifestyles, there are no significant energy savings.
Nowadays, the biggest proponents of daylight savings time are those who make money from extended evening hours. Retailers, restaurants, bars, entertainment venues, and outdoor recreation industries all generate aded revenue during the extended evening hours during daylight savings. Historically, groups like Chambers of Commerce have lobbied for extended DST, citing commercial benefits. However, while businesses may gain, the science is clear that the short-term economic cost comes at a real cost to our health.
How about we get rid of daylight savings?
Great idea!!
In the US, DST was standardized by the Uniform Time Act of 1966, which allowed states to opt out. Only Hawaii and (most of) Arizona have opted out. Dozens of states have now introduced bills to adopt a single permanent time, but federal law still requires congressional approval to make any nationwide change. If you want to contribute to getting rid of daylight savings, please check out what is going on in your own state — a great resource is SaveStandardTime, a non-profit devoted to permanent standard time.
Should we have permanent standard time or DST year-round?
Incredibly, the US has already done this experiment! In 1973, the Emergency Daylight Saving Time Energy Conservation Act was enacted, ostensibly to save energy, and “year-round” DST began in January of 1974. Unfortunately, legislators hadn’t realized that there is a big difference in morning light between summer and winter. Clocks being an hour earlier is no big deal in the summer. But with the short days in the wintertime, it quickly became apparent that setting clocks an hour earlier in the wintertime meant dark, cold, and dangerous mornings. Specifically, there was concern that children were walking to school in the dark, increasing risk of car accidents. Also, everyone was miserable. In less than a year, year-round daylight savings time was ended by Congress.
This experiment, as well as numerous scientific studies, support that permanent standard time is best for our health and happiness.
Tips for the upcoming “fall back” time change
Whether you like it or not, we will probably “fall back” an hour in a week or two. Some tips to make it easier and safer:
Transition a few days in advance, by short increments (15-20 minutes) each day. This is especially helpful for babies/pets.
Get light in the evening and early part of the night, to shift your circadian rhythm later. (Don’t do this if you have trouble falling asleep and/or a night owl already.)
Avoid caffeine later in the day and alcohol, as they will contribute to sleep disruption.
Avoid napping, which can spoil your sleep at night. If you think you will fall asleep in the evening because of the time change, plan an activity that is fun and preferably with other people, so that you don’t fall asleep accidentally.
If you can, move any events requiring peak performance, such as a big work presentation or the SATs, to NOT the week immediately following the time change.
Be really careful during your commute, especially your evening commute, especially if you are on foot or bike. If you can, move your evening commute earlier or work from home for a few days after the time change.
If you are a night owl, enjoy Fall Back Day! This year it lands on Halloween weekend. Whoooo! 🦉
Weed L, Zeitzer JM. Circadian-informed modeling predicts regional variation in obesity and stroke outcomes under different permanent US time policies, Proc. Natl. Acad. Sci. U.S.A. 122 (38) e2508293122, https://doi.org/10.1073/pnas.2508293122 (2025).
Woods AN, Weast RA, Monfort SS. Daylight saving time and fatal crashes: The impact of changing light conditions. J Safety Res. 2025 Jul;93:200-205. doi: 10.1016/j.jsr.2025.02.010. Epub 2025 Feb 25. PMID: 40483055.
