This Sunday, November 1st marks the end of Daylight Saving Time in the United States, when clocks “fall back” one hour at 2:00 AM your local time.

Nobody hated “falling back” more than my wife when she worked night shift.

While I tucked myself into bed, excited for an extra hour of sleep, she prepared to watch the clock hit 2 a.m. twice.

Which meant an extra hour tacked onto an already long shift. It also meant paying close attention to medication administration and other cares that had to be timed precisely. And for whatever reason, the shifts around that time of year never seemed to go smoothly. They always brought more than their share of crazy situations.

Turns out, she may have been onto something. Research suggests these twice-a-year clock changes affect our sleep, mood, and even our health in ways most of us never notice.

Let’s dive into it all!

So how did we end up changing our clocks in the first place?

The U.S. first adopted daylight saving time (DST) in 1918 to save fuel during World War I.

For decades after, there was no national rule. States, counties, and even cities picked their own dates, and it got messy. In May 1965, St. Paul started DST two weeks ahead of the rest of the state, while Minneapolis stuck with state law. For two weeks, the Twin Cities were an hour apart, causing a ton of confusion (Star Tribune).

The next year, Congress passed the Uniform Time Act of 1966, which standardized the dates nationwide and let states opt out entirely (like Arizona and Hawaii, more on that later).

In 1974, during the oil crisis, Congress tried year-round DST. However, negligible energy savings and rising safety concerns, following morning traffic accidents involving students, turned public opinion fast, and it was repealed within the year.

The last big change came in 2007, when DST was stretched to today’s March to November window (from April through October), with a push from industries that benefit from long evenings, like retail and golf.

So what is the situation today?

Almost nobody likes the clock switching.

The fight is over which clock to keep.

On July 14, 2026, the U.S. House passed the Sunshine Protection Act 308 to 117, which would make daylight saving time permanent. It’s now stuck in the Senate.

The case for permanent daylight saving time is mostly about evenings. More light after work for recreation, shopping, and eating out, which is why golf, retail, and restaurant groups back it. Some studies suggest less evening crime. And it’s popular with lawmakers: 19 states, including Minnesota, have already passed laws to adopt it if Congress allows.

The case for permanent standard time is mostly about mornings. Sleep scientists say it best matches our body clocks, which is why the American Academy of Sleep Medicine and 20 other groups (including the National Safety Council and National PTA) back it. There’s a safety argument too. Permanent DST would push winter sunrises an hour later, putting kids at bus stops and commuters on the road in the dark.

Since this is a health blog, let’s dig into that health case.

So what does the health research say?

First, a quick primer on why an hour matters at all.

Our bodies run on a circadian rhythm, a roughly 24-hour internal clock embedded in nearly every cell. It controls our physical, mental, and behavioral processes, and it takes its cues almost entirely from light hitting special receptors in our eyes. (I go deeper in the circadian lighting post.)

Bright morning light shuts off melatonin, brings on a natural rise in cortisol that helps you feel alert, and starts a countdown so that melatonin returns at the right time that night. Through the middle of the day, steady daylight keeps that signal strong, supporting your energy, mood, and focus. As natural light fades in the evening, that absence of light cues the brain to wind down and start preparing for sleep.

Now, springing forward is clearly harmful.

When we knock our circadian system off by even an hour overnight, the effects show up fast.

The Monday after we spring forward, heart attacks jump 24% (based on 42,000+ Michigan hospital admissions). Fatal car crashes rise 6% that week, about 28 extra deaths a year, and more than 8% on the western edge of time zones.

And research points to permanent standard time.

Standard time is built so the sun is roughly overhead at noon. Daylight saving time moves the clock an hour ahead of the sun, so we get less light in the morning and more in the evening.

Remember, morning light is what resets our internal clock each day. It’s the signal that pulls our clock earlier and keeps it on a 24-hour schedule. Under DST, we get less of it right away in the morning when we need it. Then brighter evenings push the other way, delaying melatonin and making it harder to fall asleep at a reasonable hour.

So our internal clock drifts later. We get sleepy later, and we’d naturally wake up later. But our alarms, commutes, and school start times don’t move.

That leaves us squeezed from both ends: a bedtime our body keeps pushing later, and a wake time our schedule won’t give up. The difference comes out of our sleep quality. And it happens every weekday, for about eight months a year.

How do we know it actually costs us?

Sleep is when our body does its most important repair work. Short or poor-quality sleep is linked to obesity, diabetes, high blood pressure, heart disease, stroke, and mental distress.

For the nerds. So the real question is whether the clock itself is costing us sleep, and health, at a population level. And researchers found an interesting way to test this.

Along a time zone line, two neighboring counties can share the same weather, jobs, and school schedules. The big difference is that the sun sets about an hour later by the clock on one side. Cross the line heading east, and it’s a lot like moving onto permanent DST.

Economists Osea Giuntella and Fabrizio Mazzonna used that setup to compare people on either side of U.S. time zone borders, pulling from national time-use surveys plus CDC and Census data. People on the late-sunset side slept about 19 fewer minutes a night and were more likely to get under six hours. They had higher rates of obesity, diabetes, heart disease, and breast cancer.

And last year a Stanford study in PNAS modeled all three options county by county. Any fixed clock beat switching, but permanent standard time came out ahead. Compared to switching, it would prevent an estimated ~300,000 strokes and ~2.6 million cases of obesity a year, versus about 220,000 and 1.7 million for permanent DST (Stanford Medicine).

So does it depend on where you live?

Yes, a lot. And Minnesota is a great example, because it stretches across both things that matter: how far north you are, and how far west you sit in your time zone.

Maps of Minnesota comparing the latest winter sunrise times and days with a post-8am sunrise under permanent standard time versus permanent daylight saving time
cc: Save Standard Time

Under permanent standard time, the latest winter sunrise runs from about 7:40 a.m. in the southeast corner to about 8:20 a.m. in the far northwest. Most of the state, including the Twin Cities, never sees the sun come up after 8 a.m. Only the northwest corner does, for up to about 60 days a year.

Under permanent DST, the whole state gets dark mornings. The latest sunrise runs from about 8:40 a.m. in the southeast to about 9:20 a.m. in the northwest, and every part of Minnesota sees roughly 100 to 130 days a year with sunrise after 8 a.m. In the Twin Cities, that’s about 110 days, from early November through late February. In other words, most of the school year’s darkest stretch would start with kids at the bus stop before sunrise.

The tradeoff flips in summer. Under permanent standard time, Minneapolis would see sunrise around 4:24 a.m. in June and sunset around 8:05 p.m. (versus 9:05 p.m. today). Under permanent DST, summer looks the same as it does now.

All this being said, there is no perfect option.

So what can you do inside, no matter which clock wins?

Start with morning light. Open the blinds as soon as you’re up, and have your coffee or breakfast next to your brightest window. That first hit of daylight is what keeps your clock on time. On dark Minnesota winter mornings, a light therapy (SAD) lamp helps fill the gap. I keep one in my office and run it from the morning until about 11 a.m.

Then cut the light at night. After sunset, switch from overhead lights to lamps, use warm bulbs (2700K or lower), and put the screens down when you can. Bright, cool light in the evening is the same signal as DST: it tells your brain it’s earlier than it is.

Make the bedroom dark. Blackout curtains block streetlights, early summer sunrises, and (if we ever go to permanent standard time) those 4:24 a.m. June mornings. (Full bedroom guide here.)

Enjoy the extra hour of sleep (unless you’re working the night shift),

Hunter

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