Daylight saving time ends on Sunday. Here’s What Happens to Your Body When the Times Change

Plan for a good hour of extra sleep as most of America “falls back” to standard time. But also make sure you get outside to enjoy the morning sun – this will help your body clock reset faster.

Daylight saving time ends at 2 a.m. local time on Sunday, which means you need to set your clock back an hour before going to bed. Standard Time will last until March 8, when we will “forward” again with the return of Daylight Saving Time.

There are a lot of complaints about time changes twice a year. Spring change tends to be harder, losing that hour of sleep we’re supposed to get back in the fall. But many people also mourn the end of daylight saving time in the fall, when days are already getting shorter and moving the clocks can mean less daylight after school or work for exercise or outdoor fun.

Some health groups, including the American Medical Association and the American Academy of Sleep Medicine, have long advocated adopting standard time year-round.

New research from Stanford University agrees, finding that changing our minds is the worst option for our health. The study showed that sticking to either time option would be a little healthier, but they found that permanent standard time is slightly better because it aligns more with the sun and human biology, something called our circadian rhythm.

“The best way to think about it is as if the central clock is like a conductor and each of the organs is a different instrument,” said Jamie Zeitzer, co-director of the Center for Sleep and Circadian Sciences at Stanford.

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More light in the morning and less at night is essential to keeping this rhythm on schedule – all instruments in sync. When the clock is regularly disrupted by time changes or other reasons, he said each of the body’s organ systems, such as the immune system or metabolism, “just works a little less well.”

Most countries do not observe daylight saving time. For those that do – primarily in North America and Europe – the date the clocks are changed varies. In the United States, Arizona and Hawaii do not change and remain on standard time.

Here’s what you need to know about the biannual ritual.

How the body reacts to light

The brain has a master clock that is set based on exposure to sunlight and darkness. This circadian rhythm is an approximately 24-hour cycle that determines when we become sleepy and when we are more alert. Patterns change with age, one reason why young people who mature early become difficult-to-wake teenagers.

Morning light resets the rhythm. In the evening, levels of a hormone called melatonin begin to increase, triggering sleepiness. Too much light in the evening – whether from later outside hours, during daylight saving time, or artificial light like computer screens – delays this increase and the cycle becomes out of sync.

WATCH: Ditch the switch? Senators debate future of daylight saving time

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

How do time changes affect sleep?

Even a time change can disrupt sleep schedules, because even though the clocks change, work and school start times remain the same.

Switching to Daylight Saving Time in the spring can be a little more difficult, as darker mornings and lighter evenings make it harder to fall asleep on time. Those early days were associated with an increase in car accidents and even a slight increase in heart attacks.

Some people with seasonal affective disorder, a type of depression typically linked to shorter days and less sunlight in fall and winter, may also have difficulty.

Many people adapt easily, for example when recovering from jet lag after traveling. But a change in schedule can add pressure on shift workers whose schedules are already out of sync with the sun, or those who are regularly sleep deprived for other reasons.

About one in three American adults sleep less than the recommended seven hours a night, and more than half of American teens don’t get the recommended eight hours on weeknights.

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

How to prepare for the time change

In the fall and spring, changing your bedtime by as little as 15 minutes per night in the days leading up to the change can help make it easier to get used to.

But morning sunlight is essential for resetting your circadian rhythm and promoting healthy sleep. If you can’t go out, sit near the windows.

Will the United States ever get rid of the time change?

In Congress, a bill called the Sunshine Protection Act, which proposes to make daylight saving time permanent, has stalled in recent years.