Millions of Americans in 48 states will set their clocks one hour ahead next weekend, launching nearly eight months of longer evening daylight during the spring and summer months.
As daylight saving time approaches next weekend, here’s what you should know
The time shift begins March 9, when clocks spring forward an hour until early November.
The Minnesota Star Tribune
March 1, 2025 at 2:24AM
The price? Losing an hour of sleep.
Here’s what to know as daylight saving time approaches at 2 a.m. on March 9.
A national war effort
The system for advancing clocks to shift daylight hours became official in the United States on March 19, 1918, when the Standard Time Act was signed into law, according to the U.S. Department of Defense. The law was intended to save energy costs during World War I.
About a year and a half after the war ended in 1918, the law was rescinded. Daylight saving time was again implemented during World War II, but dropped in 1945 when the war ended.
It wasn’t until the Uniform Time Act of 1966 that a consistent daylight saving time system was established twice a year, according to the U.S. Department of Transportation. It authorized state governments to exempt themselves from the system, independent of federal government permission.
A year-round system
Minnesota is among 20 states that have enacted legislation or passed resolutions in the last six years to implement year-round daylight saving time, according to the National Conference of State Legislatures. Federal law does not currently allow for a full-time system, meaning that Congress must approve the change prior to the states.
The U.S. Senate in 2022 passed the Sunshine Protection Act, which would effectively establish daylight saving time as the permanent standard time. However, no further action on the bill was taken.
Prior to taking office for his second term, President Donald Trump in December announced his opposition to daylight saving time in a post on Truth Social.
“The Republican Party will use its best efforts to eliminate Daylight Saving Time, which has a small but strong constituency, but shouldn’t!” Trump wrote. “Daylight Saving Time is inconvenient, and very costly to our Nation.”
So far, the Trump administration has not taken formal action to change the law.
Health implications
Scientists and medical professionals have openly expressed concern about daylight saving time, citing cost and adverse health effects.
Recent data from a YouGov poll indicates many Americans would prefer to eliminate the changing of clocks entirely. It found 63% of U.S. adults support the termination of daylight saving time, with 31% valuing their health and human biological circadian rhythms most.
Artificially shifting the clock forward interferes with human circadian biology and has been associated in studies with increased health risks, according to a 2020 American Academy of Sleep Medicine position statement.
The trillions of cells in the human body possess a genetic clock that allows us to be in tune with our environment and gives us the tools to adapt and perform at our best, according to Dr. Wajahat Khalil, an associate professor of medicine at the University of Minnesota.
Khalil said our internal clocks typically run slightly longer than 24 hours, causing disruption when daylight time shifts are imposed. That can lead to sleep deprivation, poor alertness, impaired physical performance and digestion issues, he said.
When time shifts, whether because of jet travel or daylight saving time, it forces a condition called dyssynchrony, Khalil said, where the heart’s chambers beat unevenly.
“And what we need to know is that dyssynchrony has consequences all the way down to our trillions of cells,” he said.
Tips for transitioning times
Whether you support daylight saving time, want to see it eliminated or are among the 32% of Americans who want to make the system permanent, there are things you can do to better prepare your body for the time shift.
Being consistent with sleep and wake cycles, adjusting sleep schedules before the time change, finding early morning light exposure and adjusting mealtimes can minimize negative effects, according to Khalil.
Light exposure is the most important mitigating factor, signaling to the body when it’s time to be awake and alert, he said. What time we eat, exercise, sleep and socialize are additional environmental cues that affect our body’s internal clock.
By maintaining structured habits, we can help synchronize our circadian rhythms, which regulate various physiological and behavioral processes.
Khalil generally recommends eating two to three hours before sleeping, getting 10 to 15 minutes of sunlight in the morning and sleeping 15 to 20 minutes earlier each night in the two to three nights leading up to the time change. Resynchronization can take the average person three to seven days.
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