Plan on a glorious extra hour of sleep as most of America “falls back” into standard time. But make sure to get outside for some morning sun, too — it’ll help your body clock reset faster.
Daylight saving time ends at 2 a.m. local time Sunday, which means you should set your clock back an hour before you go to bed. Standard time will last until March 8 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. The spring switch tends to be 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.
Some health groups, including the American Medical Association and American Academy of Sleep Medicine, have long urged adopting standard time year-round.
New research from Stanford University agrees, finding that switching back-and-forth is the worst option for our health. The study showed sticking with either time option would be a bit healthier, but they found permanent standard time is slightly better — because it aligns more with the sun and human biology, what’s called our circadian rhythm.
“The best way to think about it is as if the central clock were like a conductor of an orchestra and each of the organs were a different instrument,” said Jamie Zeitzer, who co-directs Stanford’s Center for Sleep and Circadian Sciences.
More light in the morning and less at night is key to keeping that rhythm on schedule — all the 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 — mostly in North America and Europe — the date that clocks are changed varies. In the U.S., Arizona and Hawaii don’t change and stay on standard time.
Here’s what to know about the twice-yearly ritual.
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 resets the rhythm. By evening, levels of a hormone called melatonin begin to surge, triggering drowsiness. Too much light in the evening — whether from later time outdoors doing 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.
Even an hour change on the clock can throw off sleep schedules because even though the clocks change, work and school start times stay the same.
The spring change to daylight saving time can be a little rougher as 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.
Some people with seasonal affective disorder, a type of depression usually linked to the shorter days and less sunlight of fall and winter, may struggle too.
Many people easily adjust, 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.
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.
In Congress, a bill named the Sunshine Protection Act that proposes making daylight saving time permanent has stalled in recent years.
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.
FILE - The sun rises, seen through morning mist and silhouetted maple leaves, as trees turn to fall foliage colors, Tuesday, Oct. 7, 2025, in Auburn, N.H. (AP Photo/Charles Krupa, File)
FILE - Clockmakers Rich Finn, left, and Tom Erb adjust the time zone controllers on a series of clocks that'll be installed at Paine Field in Everett, Wash., at the Electric Time Company, Wednesday, Oct. 30, 2024, in Medfield, Mass. (AP Photo/Charles Krupa, File)
Iran eased some restrictions on its people and for the first time in days allowed them to make phone calls abroad via their mobile phones on Tuesday. It did not ease restrictions on the internet or allow texting services to be restored as the toll from days of bloody protests against the state rose to at least 646 people killed.
Although Iranians were able to call abroad, people outside the country could not call them, several people in the capital told The Associated Press.
The witnesses, who spoke on condition of anonymity for fear of reprisal, said SMS text messaging still was down and internet users inside Iran could not access anything abroad, although there were local connections to government-approved websites.
It was unclear if restrictions would ease further after authorities cut off all communications inside the country and to the outside world late Thursday.
Here is the latest.
The United Nations human rights chief is calling on Iranian authorities to immediately halt violence and repression against peaceful protesters, citing reports of hundreds killed and thousands arrested in a wave of demonstrations in recent weeks.
“The killing of peaceful demonstrators must stop, and the labelling of protesters as ‘terrorists’ to justify violence against them is unacceptable,” U.N. High Commissioner for Human Right Volker Türk said in a statement Tuesday.
Alluding to a wave of protests in Iran in 2022, Türk said demonstrators have sought “fundamental changes” to governance in the country, “and once again, the authorities’ reaction is to inflict brutal forces to repress legitimate demands for change.”
“This cycle of horrific violence cannot continue,” he added.
It also was “extremely worrying” to hear some public statements from judicial officials mentioning the prospect of the use of the death penalty against protesters through expedited judicial proceedings, Türk said.
“Iranians have the right to demonstrate peacefully. Their grievances need to be heard and addressed, and not instrumentalized by anyone,” Türk said.
Finland’s foreign minister said she is summoning the Iranian ambassador after authorities in Tehran restricted internet access.
“Iran’s regime has shut down the internet to be able to kill and oppress in silence," Elina Valtonen wrote in a social media post Tuesday, adding “this will not be tolerated. We stand with the people of Iran — women and men alike.”
Finland is “exploring measures to help restore freedom to the Iranian people” together with the European Union, Valtonen said.
Separately, Finnish police said they believe at least two people entered the courtyard of the Iranian embassy in Helsinki without permission Monday afternoon and tore down the Iranian flag. The embassy’s outer wall also was daubed with paint.
Iranian security forces arrested what a state television report described as terrorist groups linked to Israel in the southeastern city of Zahedan.
The report, without providing additional details, said the group entered through Iran’s eastern borders and carried U.S.-made guns and explosives that the group had planned to use in assassinations and acts of sabotage.
The Israeli military did not immediately comment on the allegations.
Nobel Peace Prize laureate Malala Yousafzai expressed her support for the growing protest movement roiling Iran, hailing people who have “long warned about this repression, at great personal risk.”
“The protests in Iran cannot be separated from the long-standing, state-imposed restrictions on girls’ and women’s autonomy, in all aspects of public life including education. Iranian girls, like girls everywhere, demand a life with dignity,” Yousafzai wrote on X.
“(Iran’s) future must be driven by the Iranian people, and include the leadership of Iranian women and girls — not external forces or oppressive regimes,” she added.
Yousafzai was awarded the peace prize in 2014 at the age of 17 for her fight for girls’ education in her home country, Pakistan. She is the youngest Nobel laureate.
The French Foreign Ministry said it has “reconfigured” its embassy in Tehran after reports that the facility's nonessential staff left Iran earlier this week.
The embassy's nonessential staff left the country Sunday and Monday, French news agency Agence France-Presse reported.
The ambassador remained on site and the embassy continued to function, the ministry said late Monday night.
Angela Charlton contributed from Paris.
German Chancellor Friedrich Merz said he believes the Iranian government is in its “final days and weeks,” as he renewed a call for Iranian authorities to end violence against demonstrators immediately.
“If a regime can only keep itself in power by force, then it’s effectively at the end,” Merz said Tuesday during a visit to Bengaluru, India. “I believe we are now seeing the final days and weeks of this regime. In any case, it has no legitimacy through elections in the population. The population is now rising up against this regime.”
Merz said he hoped there is “a possibility to end this conflict peacefully," adding that Germany is in close contact with the U.S. and European governments.
The Israeli military said it continues to be “on alert for surprise scenarios” due to the ongoing protests in Iran, but has not made any changes to guidelines for civilians, as it does prior to a concrete threat.
“The protests in Iran are an internal matter,” Israeli military spokesperson Brig. Gen. Effie Defrin wrote on X.
Israel attacked Iran’s nuclear program over the summer, resulting in a 12-day war that killed nearly 1,200 Iranians and almost 30 Israelis. Over the past week, Iran has threatened to attack Israel if Israel or the U.S. attacks.
Mobile phones in Iran were able to call abroad Tuesday after a crackdown on nationwide protests in which the internet and international calls were cut. Several people in Tehran were able to call The Associated Press.
The AP bureau in Dubai, United Arab Emirates, was unable to call those numbers back.
Witnesses said the internet remained cut off from the outside world. Iran cut off the internet and calls on Thursday as protests intensified.
Activists said the death toll from ongoing protests have at least 646 people.
The U.S.-based Human Rights Activists News Agency, which has been accurate in previous unrest in recent years and gave the latest death toll early Tuesday. The agency relies on supporters in Iran cross-checking information.
The agency said 512 of the dead were protesters and 134 were security force members.
More than 10,700 people have been detained over the two weeks of protests, the agency said.
This frame grab from videos taken between Jan. 9 and Jan. 11, 2026, and circulating on social media purportedly shows images from a morgue with dozens of bodies and mourners after crackdownon the outskirts of Iran's capital, in Kahrizak, Tehran Province. (UGC via AP)
This frame grab from videos taken between Jan. 9 and Jan. 11, 2026, and circulating on social media purportedly shows images from a morgue with dozens of bodies and mourners after crackdown on the outskirts of Iran's capital, in Kahrizak, Tehran Province. (UGC via AP)
This frame grab from videos taken between Jan. 9 and Jan. 11, 2026, and circulating on social media purportedly shows images from a morgue with dozens of bodies and mourners after crackdown on the outskirts of Iran's capital, in Kahrizak, Tehran Province. (UGC via AP)
Protesters hold up placards and flags as they demonstrate outside the Iranian Embassy in London, Monday, Jan. 12, 2026. (AP Photo/Alastair Grant)
Shiite Muslims hold placards and chant slogans during a protest against the U.S. and show solidarity with Iran in Lahore, Pakistan, Sunday, Jan. 11, 2026. (AP Photo/K.M. Chaudary)
Activists carrying a photograph of Reza Pahlavi take part in a rally supporting protesters in Iran at Lafayette Park, across from the White House, in Washington, Sunday, Jan. 11, 2026. (AP Photo/Jose Luis Magana)
Protesters burn the Iranian national flag during a rally in support of the nationwide mass demonstrations in Iran against the government in Paris, Sunday, Jan. 11, 2026. (AP Photo/Michel Euler)
People attend a rally in Frankfurt, Germany, Monday, Jan. 12, 2026. (Boris Roessler/dpa via AP)
A picture of Ayatollah Ali Khamenei is set alight by protesters outside the Iranian Embassy in London, Monday, Jan. 12, 2026. (AP Photo/Alastair Grant)
