How Does Daylight Saving Time Work?
Published: October 24, 2018
Updated: March 9, 2021
by Johnna Kaplan
Although we dutifully adjust our lives for it twice a year, the whole “Spring forward, fall back” phenomenon can be puzzling. For many people, when the time change approaches in spring or fall, it brings with it at least a moment of confusion: How does daylight saving time work, again? What day do we do this, and what time exactly do we change our clocks? Are we gaining an hour, or losing one? If that hour is truly lost, where does it go? And is it Daylight Saving or Daylight Savings Time?
That last one’s easy. Strange as it sounds if you usually say the “s,” the proper name is Daylight Saving Time. As for the rest of it, here are the facts you need to know about springing forward and falling back.
Why Does Daylight Saving Time Exist?
The first person known to have suggested a seasonal adjustment of time was none other than Benjamin Franklin. In 1784, he noted that sleeping in despite the sun’s rising earlier in the summer was a waste of good daylight. He suggested, humorously, not a nationwide changing of clocks but rather a volley of early morning cannon fire to rouse people from their beds. Several other innovators around the world had similar ideas over the next century. Some proposed more serious plans to do something about it, but ultimately these were seen as impractical and unwelcome.
The urgent need to conserve fuel during World War I finally made 31 nations implement a version of Daylight Saving Time or DST. After the war was over, most of them returned to “normal,” but soon enough World War II began. Then, 52 countries adopted the energy-saving schedule adjustment. Some changed their clocks for the whole year, including the United States. The U.S. remained on what was then called “wartime” from 1942 to 1945. (Daylight Saving Time would be extended again during the oil crisis of the 1970s.) After the war, when mandatory nationwide “wartime” ended, clock-related matters were left to state and local governments to regulate (or not) as they chose.
The federal government didn’t attempt to standardize the process again until 1966. It enacted the Uniform Time Act and established dates and times for those areas choosing to change their clocks. Further adjustments were made in 1986 and 2007. Today most people in the U.S. change their clocks at the agreed-upon time and date twice a year.
Does Everyone Observe the Time Change?
There are exceptions, however. The U.S. territories of Puerto Rico, Guam, American Samoa, the U.S. Virgin Islands, and the Northern Mariana Islands do not observe daylight saving time, nor does the state of Hawaii. In the lower 48, only Arizona does not use DST. However, the Navajo Nation, located within Arizona, does, while the Hopi Reservation, located within the Navajo Nation, does not. In most places, an extra hour of daylight saves on fuel used to heat and illuminate homes and businesses. This was not the case in Arizona where consumption of energy skyrocketed with even one extra hour of daylight. So after the first year, most of Arizona opted out of Daylight Saving Time.
Indiana mandated Daylight Saving Time observance in 2006. Before that, some counties in the state changed their clocks while the others didn’t – compounding the confusion in a state spread across two time zones.
Canada and Mexico change their clocks, although there are some regional exceptions and slight differences in Daylight Saving Time start and end dates. Much of the European Union uses Daylight Saving Time, for now. There is talk of abandoning the practice, as some European countries not in the EU, and Russia, have already done. In the Southern Hemisphere, countries that practice Daylight Saving Time spring back and fall forward. Most Asian and African nations do not use Daylight Saving Time at all.
Are We Gaining or Losing an Hour?
Twice a year, most people find themselves wondering, how does daylight saving time work? In the spring, we “spring forward,” moving our clocks ahead one hour so that 1:59 a.m. turns not to 2 a.m. as usual but to 3 a.m., skipping—or losing—an hour. Most people don’t think about it, as they are asleep, but this spring day is only 23 hours long.
In the fall, when we “fall back,” the clocks go from 1:59 a.m. back to 1 a.m. instead of to the usual 2 a.m., repeating—or gaining—an hour. This fall day is 25 hours long, and the hour between 1 a.m. and 2 a.m. repeats. That means if a baby is born at, say, 1:45 a.m.—or if for some reason you’re awake and have something scheduled at that time—it’s important to specify at which 1:45 a.m. the birth or event is taking place.
How Does Daylight Saving Time Work?
Of course, Daylight Saving Time does not have any effect on the sun or the changing of the seasons. It simply alters the way we experience those aspects of nature through our clocks and calendars. By shifting those points in the day when we decide it’s time to get up, go to work, and eat dinner, we can have slightly more daylight hours toward the end of our days. This is the case for nearly eight months out of the year.
When it comes to how does daylight saving time work, the simplest facts are:
- Daylight Saving Time in the United States begins at 2 a.m. on the second Sunday in March.
- Daylight Saving Time ends at 2 a.m. on the first Sunday in November.
These days, most clocks, like on cell phones, change on their own. However, we still need to pay attention to those that don’t like old-fashioned alarm clocks, watches, and the digital clocks in cars and on stoves.
Daylight Saving Time starts this year on Sunday, March 14, 2021 and ends on Sunday, November 7, 2021.
What Are the Pros and Cons of Daylight Saving Time?
Daylight Saving Time feels entrenched in our society, but it is not without controversy, and it is not a given. Countries have been known to give it up entirely, even decades after implementing it. More are likely to follow, as further research evaluates the benefits and drawbacks of this regular hiccup in our schedules.
Historically, advocates for Daylight Saving Time have said it saves energy. With more daylight, people use less electricity to light their homes and spend less time running appliances. Some say it reduces traffic accidents. When it’s lighter later, the reasoning goes, we spend less time commuting in the dark.
Other celebrated aspects of Daylight Saving Time range from the wholesome to the financial:
- Children have more time to play outside.
- Adults have more time to shop and stimulate local economies.
- More daylight provides more time for events, giving a financial boost to the sports and recreation industries.
Opponents of Daylight Saving Time claim that the practice may not save much energy after all. They say it may even increase the use of electricity in some cases, like cooling homes in climates like Arizona’s. Similarly, they say Daylight Saving Time might not actually lead to an overall improvement in public safety, and that sleep-deprived workers and drivers are more likely to make deadly mistakes.
Detractors also claim that adjusting to the time change interrupts our natural cycles of sleep, leading to fatigue, a greater susceptibility to illness, and even a brief increase in heart attacks. Interestingly, despite the common belief that DST was instituted to benefit farmers, the agriculture industry fought against the switch when it was first introduced. Having to adjust to the clock, rather than work with the sun as usual, disrupted their routines with detrimental effects. Many farmers still oppose it today.
Why is the Time Change So Confusing?
Although many contest the perks and drawbacks of Daylight Saving Time, no one disputes the time change is confusing – and not just because it might make you late for a morning meeting. In 1922, President Warren G. Harding issued an executive order mandating an earlier start for federal workers, while letting other employers in D.C. decide whether to join in. This effectively turned Washington into a city with no set schedule, and the resulting chaos was so overwhelming that Harding was forced to repeal his order.
Even today, there are aspects of life that don’t fit neatly into our manipulation of the clock. Amtrak trains running on the two nights of the year when Daylight Savings Time begins and ends have to be creative. They must either stop and wait for an hour or speed up and attempt to make up for lost time. And we can only guess what Benjamin Franklin would have thought of the headaches his idea now causes for airlines trying to schedule international flights. They juggle flight schedules among nearly 200 countries in different hemispheres, each with a quirky clock-changing system of its own.
What Else Should I Do When I Change My Clocks?
You’re probably familiar with the idea of changing the batteries in your smoke detectors every time you change your clocks. The International Association of Fire Chiefs has been advocating tying this life-saving task to that other twice-yearly chore for the past 30 years. It works because announcements about turning clocks forward or back are nearly unavoidable. And even if you do manage to miss the reminders, you’ll certainly notice the next day when your phones and computers have automatically adjusted themselves.
The time change is a good opportunity to complete other household tasks that should be done a few times a year. So what else might you link to your Daylight Saving Time fall and spring routines?
- Along with smoke alarms, change the batteries in carbon monoxide detectors and any other safety monitors in your house.
- Flip your mattresses and wash your pillows.
- Check your home and auto emergency kits to make sure you’re prepared for a storm or power outage.
- Replace air filters to help ensure heating and air conditioning systems are running efficiently.
- Declutter your bathroom and kitchen and get rid of expired food, products and medicines.
- Deep clean anything that isn’t part of your regular cleaning routine, like the oven.
And—while you’re at it—use these biannual blips in the passage of time as reminders to take care of other things that are important to you. Even if the adjustment is difficult for you, be thankful that at least you’re not being awakened by the blast of a cannon.