How daylight saving time changes affect you and what you can do about it

An extra hour of sleep is on the way for most Americans, though the “fall back” to standard time will bring darker afternoons, too.

One tip: Try to get outside for some morning sun — it’ll help your body clock reset faster.

Daylight saving time ends at 2 a.m. local time on Sunday, which means you should set your clock back an hour before you go to bed. Standard time will last until March 14, when we will again “spring forward” with the return of daylight saving time.

There’s a lot of grumbling about the twice-a-year time changes. An AP-NORC poll last year found that only 12% of American adults were in favor of it, while almost half opposed it. Lawmakers in Washington took up the issue yet again over the summer.

People often find the spring switch harder, losing that hour of sleep we allegedly recover in the fall. But many people also mourn fall’s end of daylight saving time, when days already are getting shorter and moving the clocks can mean less daylight after school or work for exercise or outdoor fun. The poll found that, if forced to choose, most Americans would prefer to keep that extra hour of daylight in the evening.

But health groups, including the American Medical Association and American Academy of Sleep Medicine, have long urged adopting standard time year-round. That’s because it aligns more with the sun, which rises later in the winter, and with human biology, what’s called the circadian rhythm. Brighter mornings and less light at night are key to keeping that rhythm on track, making it easier to wake up on time and stick with healthy sleep patterns.

Most countries do not observe daylight saving time. For those that do — mostly in North America and Europe — the date that clocks are changed varies. In the U.S., Hawaii and most of Arizona don’t change and stay on standard time.

Here’s what to know about the twice-yearly ritual.

How the body reacts to light

The brain has a master clock that is set by exposure to sunlight and darkness. This circadian rhythm is a roughly 24-hour cycle that determines when we become sleepy and when we’re more alert. The patterns change with age, one reason that early-to-rise youngsters evolve into hard-to-wake teens.

Morning light is key to synchronizing that internal clock. By evening, levels of a hormone called melatonin begin to surge, triggering drowsiness. Too much light in the evening — whether from later time outdoors during daylight saving time or from artificial light like computer screens — delays that surge and the cycle gets out of sync.

And that circadian clock affects more than sleep, also influencing things like heart rate, blood pressure, stress hormones and metabolism.

How do time changes affect sleep?

Even an hour’s change on the clock can throw off sleep schedules because even though the clocks change, work and school start times stay the same.

Right after the spring change, darker mornings and lighter evenings make it harder to fall asleep on time. Those first few days have been linked to increases in car crashes and even an uptick in heart attacks.

During the fall and winter, some people with seasonal affective disorder, a type of depression usually linked to the shorter days and less sunlight, often struggle.

Many people easily adjust to the clock switch, like how they recover from jet lag after traveling. But a time change can add pressure on shift workers whose schedules already are out of sync with the sun, or those regularly sleep-deprived for other reasons.

About 1 in 3 U.S. adults sleep less than the recommended seven-plus hours nightly, and more than half of U.S. teens don’t get the recommended eight-plus hours on weeknights.

Chronic sleep deprivation is linked to heart disease, cognitive decline, obesity and numerous other problems.

How to prepare for the time change

In both fall and spring, changing bedtimes by as little as 15 minutes a night in the days before the change can help ease into it.

But sunshine in the morning is critical to helping reset your circadian rhythm for healthful sleep. If you can’t get outdoors, sit by windows.

Will the US ever get rid of the time change?

Every year, there’s talk about ending the time change. The nation even tried it in the 1970s, but it lasted less than a year after a public outcry.

The latest attempt came in July, when the U.S. House of Representatives overwhelmingly passed the Sunshine Protection Act, which would make daylight saving time permanent. President Donald Trump backs the idea and is pressuring reluctant senators to support it, even posting the cellphone number of Arkansas Sen. Tom Cotton, an opponent, on social media.

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