Daylight saving time: A century of clock changing could soon run out. How did we get here?
It happens every year. Americans move their clocks one hour forward in the spring and an hour backward in the fall. It is a practice with a 100-year history.
But the Senate passed a bill Tuesday that may change all that. If approved in Congress and signed by President Joe Biden, the Sunshine Protection Act would make daylight saving time (DST) permanent. That means no more turning back the clock for roughly half the year.
Two states, Arizona and Hawaii have already stopped observing DST. Why does most of the rest of the country continue to do so? What benefits does the time change provide? Why do others want it gone? Here's what to know:
What's behind DST?
The United States began observing the time change in 1918, copying efforts by Germany and Britain to save energy during WWI. The Standard Time Act of 1918 also established standard time zones.
Congress abandoned DST the following year — though it was reinstated during WWII — and standardized the practice under the Uniform Time Act of 1966 after states and localities could not agree on when to change their clocks.
Congress later established a six-month daylight saving period and allowed states to opt-out. In 1970, President Richard Nixon pressed the House to temporarily impose DST year-round for two years due to energy shortages, but the unpopular plan was suspended 10 months later.
What other changes did Congress make to DST?
In 1986, Congress changed the starting date from the last Sunday in April to the first Sunday of the month and ending the last Sunday in October.
More: Permanent daylight saving time? America tried it before ... and it didn't go well
The Energy Policy Act of 2005 moved the beginning of DST to the second Sunday in March, ending the first Sunday in November. This policy remains in effect today.
Are there benefits to seasonal time changes?
Some have argued that an additional hour of light in the morning benefits tourism, increases safety and saves energy. A 2020 report by the Congressional Research Service stated permanently extending DST might have a negative effect on golf course and ski resort operations and schoolchildren's morning commutes.
But the report also cited studies suggesting a link between shifts to and from DST and the increase and decrease in heart attack incidents.
Over the years, Congress has ordered a series of studies on the effects of DST. An evaluation of a 1975 Department of Transportation report found statistically significant evidence of increased fatalities among school-age children in the mornings from January-April 1974 compared to the same time frame in 1973. While darker mornings reduce driver visibility, experts said the results could not be interpreted as a "DST effect."
A 2008 Department of Energy report found negligible changes in energy savings by extending DST, though areas in the northern part of the country experienced larger electricity savings than areas in the south.
Should DST be permanently extended?
Experts say permanently extending DST comes with several benefits, including better health, safety and crime reduction.
Steve Calandrillo, a professor at the University of Washington School of Law, told lawmakers at a March 9 House Energy and Commerce Committee hearing that "darkness kills and sunshine saves."
"The evening rush hour is much more fatal than the morning rush hour for various reasons," Calandrillo said, citing more drivers on the road and more under the influence in the evening hours. "In fact, fatal vehicle on pedestrian crashes skyrocket threefold once we hit the twilight hour, once the sun goes down."
More: Senate passes bill to make daylight saving time permanent
Calandrillo also argued that criminals are more active in the hours between 6 p.m. and midnight.
"And daylight saving time has the effect of taking one hour out of their workday, right?" he said.
Lyle Beckwith, senior vice president of government relations for the National Association of Convenience Stores told the committee that DST "is good for business and commerce across the United States, and our industry urges you to keep it in place."
"Our industry has consistently found that commerce increases when the nation moves to daylight saving time," Beckwith said. "When the clocks change in the spring, people feel as though they have more time afterward to engage in the range of activities that increase commerce, from eating out, to shopping, to participating in or taking kids to a variety of outdoor activities."
Dr. Beth Malow, a practicing neurologist and sleep medicine specialist at Vanderbilt University Medical Center in Nashville, Tennessee testified at the hearing that permanent DST is a healthier choice, and cited circadian misalignment — a mismatch in the timing between work, school, sleep routines and the sun — as a health risk.
"Chronic sleep loss, circadian misalignment, or both make us more prone to a whole host of detrimental health effects throughout the lifespan, including obesity, diabetes, ADHD, depression, cardiovascular disease, cancer, and Alzheimer's disease," Malow said.
Do other countries observe DST?
More than 70 countries, including most of Europe and the United Kingdom, turn back their clocks once a year, though the beginning and end dates vary from country to country.
Contributing: The Florida Times Union
Reach out to Chelsey Cox on Twitter at @therealco.