Published: March 28, 2022 By

When Senators Marco Rubio of Florida and Edward Markey of Massachusetts introduced the bipartisan Sunshine Protection Act earlier this month, they rattled off a long list of reasons for making daylight saving time (DST) permanent.

Among them: It would enable families to spend more time outdoors in the evenings and, in doing so, help combat childhood obesity, said Rubio. And, “getting that extra hour of sunshine into people’s lives,” could improve public safety, save energy and boost mental health, said Markey.

On Monday, a state House committee unanimously approved a similar bill in Colorado.

But CU Boulder Professor Ken Wright sees it differently.

“If you look at the expert consensus from the scientific societies that focus on sleep, health and circadian rhythms, all of them agree this is a bad idea,” said Wright, who has studied the impact of light on sleep and health for 30 years. “Yes, we should be getting rid of the time change. But the science suggests we should be sticking with standard time not daylight saving time.”

CU Boulder Today spoke with Wright about the history of DST, the proposed bills that now await further hearings, and what the science says.

When and why was daylight saving time created?

It was first introduced on a large scale by the Germans during World War I to save energy. The idea was that extending evening sunlight would mean people wouldn’t use as much energy. The U.S. followed suit and has since gone back and forth between having it and not having it, including during the energy crisis of 1974, when the U.S. decided to try permanent DST for two years to save energy.

How did that go?

At first, 79% of the public was in favor of the change. However, by February, after the first winter of exposure to dark mornings, support dropped to 42% and the law was repealed after only 10 months. It didn’t save much energy, and research showed fuel usage actually increased slightly

Ken Wright

Ken Wright, professor of distinction and associate chair for integrative physiology

What would winter mornings be like if this bill passes?

As a population, we’ll be waking up more often in the darkness. For instance, this clock change would cause Colorado to lose more than two months of having sunlight in the morning before 8 a.m. and 98 days of having sunlight in the morning before 7 a.m., compared to if we were to adopt permanent standard time (ST). 

What’s wrong with dark mornings?

The winter sun that is often there to help melt the ice on our roads for the morning commute won’t be there, and more people will be driving to work or to the ski resorts in the dark, increasing risk of accidents. More Colorado children will be waiting for the morning bus in the dark. And any benefits to our children that have been gained by some schools adopting later start times (to better match adolescents’ physiological tendency to go to bed later and sleep later) will be erased.

But we’ll have more light at night? Isn’t that a good thing?

Actually no. When we get exposed to light at night, whether it be more sunlight or lights inside our house or on our devices, that sends a signal to our circadian clock that we should go to bed later and wake up later. Later sleep timing is associated with more substance use and physical and mental health problems, including obesity, depression and heart disease. It’s also associated with morning sleepiness, which contributes to accidents, poor work productivity and poor school performance.

And we’re not just getting more light at night with this change, we’re getting less morning light. Morning light is good for your health because it promotes earlier sleep timing that is more conducive to school and work start times. 

What do you make of the argument that getting an ‘extra hour of sunshine’ will make kids more active?

Regardless of what happens, we are still going to have the same amount of sunlight across 24 hours. What will change is how we schedule ourselves relative to the sun. Permanent DST and permanent ST have the same number of days with sunset after 7 p.m. during the summer holidays (mid-May to mid-August), so permanent ST will have little impact on many outdoor sports in the summer.

Yes, there would be fewer sunsets after 8 p.m. under permanent ST, but any sports can continue at night after sunset as is currently done with electric lights. This is likely why the yearly shift to DST does not make kids more active.

You say we should do away with the time change. Why?

There is no question the change itself is associated with problems. In the days after the “spring ahead” we just went through, we get less sleep and wake up at a time when our brains are telling us we should still be sleeping. There are lots of associated risks, including an increase in fatal motor vehicle accidents and in heart attacks and strokes.

What does the research say? Is permanent DST or ST healthier?

We don’t have any studies that have, say, compared 10 years of one to 10 years of the other. But we do have studies where they compare people who live on the western edge of a time zone to people living on the eastern edge of the adjacent time zone. They are essentially in the same region, with the sun coming up and going down for them about the same time, but the one on the western edge has the sun setting an hour later according to the clock on the wall, much like what would happen with DST.

These studies have found that people on the western edge of the time zone slept less, were more likely to be overweight and obese, and had higher risks of diabetes, heart attacks and cancer. 

What’s your takeaway for lawmakers mulling this decision?

Major international scientific societies have put out expert opinion papers that are unanimous in that we should adopt permanent standard time, and Arizona and Hawaii have used permanent standard time since the 1960s. We should follow suit.