Saving Time, Saving Energy
Daylight Saving Time: Its History and Why We Use It
by Bob Aldrich, Webmaster (retired)
California Energy Commission
Spring forward...Fall back....
It's ingrained in our consciousness almost as much as the A-B-Cs or our spelling reminder of "i before e...." And it's a regular event, though perhaps a bit less regular than the swallows coming back to Capistrano. (Though that may even change with the impacts of global climate change.)
Yet in those four words is a whole collection of trivia, facts and common sense about Daylight Saving Time.
Beginning in 2007, Daylight Saving Time is extended one month and begins for most of the United States at:
2 a.m. on the Second Sunday in March
and lasts until
2 a.m. on the First Sunday of November.
The new start and stop dates were set in the Energy Policy Act of 2005.
Daylight Saving Time - for the U.S. and its territories - is NOT observed in Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands, and by most of Arizona (with the exception of the Navajo Indian Reservation in Arizona).
Indiana, which used to be split with a portion of the state observing DST and the other half not, is now whole. In the past, counties in the Eastern Time Zone portion of the state did not observe DST. They were on standard time year round. A state law was passed in 2005 that has the entire state of Indiana observing DST beginning in April 2006.
Indiana isn't the only state that wanted to change daylight saving time. California asked for federal "approval" to move to a "year-round" Daylight Saving Time in 2001-2002 because of its energy crisis. (See below.)
According to Mining Co. Guide to Geography, DST is also observed in about 70 countries:
"Other parts of the world observe Daylight Saving Time as well. While European nations have been taking advantage of the time change for decades, in 1996 the European Union (EU) standardized an EU-wide "summertime period." The EU version of Daylight Saving Time runs from the last Sunday in March through the last Sunday in October. During the summer, Russia's clocks are two hours ahead of standard time. During the winter, all 11 of the Russian time zones are an hour ahead of standard time. During the summer months, Russian clocks are advanced another hour ahead. With their high latitude, the two hours of Daylight Saving Time really helps to save daylight. In the southern hemisphere where summer comes in December, Daylight Saving Time is observed from October to March. Equatorial and tropical countries (lower latitudes) don't observe Daylight Saving Time since the daylight hours are similar during every season, so there's no advantage to moving clocks forward during the summer."
Daylight Saving Time Saves Energy
One of the biggest reasons we change our clocks to Daylight Saving Time (DST) is that it reportedly saves electricity. Newer studies, however, are challenging long-held reason.
In general, energy use and the demand for electricity for lighting our homes is directly connected to when we go to bed and when we get up. Bedtime for most of us is late evening through the year. When we go to bed, we turn off the lights and TV.
In the average home, 25 percent of all the electricity we use is for lighting and small appliances, such as TVs, VCRs and stereos. A good percentage of energy consumed by lighting and appliances occurs in the evening when families are home. By moving the clock ahead one hour, we can cut the amount of electricity we consume each day.
Studies done in the 1970s by the U.S. Department of Transportation show that we trim the entire country's electricity usage by about one percent EACH DAY with Daylight Saving Time.
Daylight Saving Time "makes" the sun "set" one hour later and therefore reduces the period between sunset and bedtime by one hour. This means that less electricity would be used for lighting and appliances late in the day. We may use a bit more electricity in the morning because it is darker when we rise, but that is usually offset by the energy savings in the evening.
We also use less electricity because we are home fewer hours during the "longer" days of spring and summer. Most people plan outdoor activities in the extra daylight hours. When we are not at home, we don't turn on the appliances and lights. A poll done by the U.S. Department of Transportation indicated that Americans liked Daylight Saving Time because "there is more light in the evenings / can do more in the evenings."
While the amounts of electricity saved per household are small...added up they can be very large.
In the winter, the afternoon Daylight Saving Time advantage is offset by the morning's need for more lighting. In spring and fall, the advantage is less than one hour. So, Daylight Saving Time saves energy for lighting in all seasons of the year except for the four darkest months of the year (November, December, January and February) when the afternoon advantage is offset by the need for lighting because of late sunrise.
A report was released in May 2001 by the California Energy Commission to see if creating an early DST or going to a year-round DST will help with the electricity problems the state faced in 2000-2002.
You can download an Acrobat PDF copy of the staff report, Effects of Daylight Saving Time on California Electricity Use, Publication # 400-01-13, (PDF file, pages, 5.2 megabytes).
The study concluded that both Winter Daylight Saving Time and Summer-season Double Daylight Saving Time (DDST) would probably save marginal amounts of electricity - around 3,400 megawatt-hours (MWh) a day in winter (one-half of one percent of winter electricity use - 0.5%) and around 1,500 MWh a day during the summer season (one-fifth of one percent of summer-season use - 0.20%). Winter DST would cut winter peak electricity use by around 1,100 megawatts on average, or 3.4 percent. Summer Double DST would cause a smaller (220 MW) and more uncertain drop in the peak, but it could still save hundreds of millions of dollars because it would shift electricity use to low demand (cheaper) morning hours and decrease electricity use during higher demand hours.
The Energy Commission has also published a new report titled The Effect of Early Daylight Saving Time on California Electricity Consumption: A Statistical Analysis. Publication # CEC-200-2007-004, May 27, 2007. (PDF file, 592 kilobytes)
In May 2001, the California state legislature sent a Senate Joint Resolution (SJRX2 1) to the White House and Congress asking that states be allowed to extend Daylight Saving Time year round. Congress and the White House did not act on the request because of the world-changing events of September 11, 2001. No new legislation has been passed in California since then.
A more recent study concludes that Daylight Saving Time in Indiana actually increases residential electricity demand. That study titled "Does Daylight Saving Time Save Energy? Evidence From a Natural Experiment in Indiana". (PDF file) looked at the electricity use when portions of the state finally started to observe DST. Before the new extended DST, portions of Indiana did not observe DST.
Some have wondered whether this study would be true for the entire United States. Initial analysis by staff of the California Energy Commission says a similar study may not yield the same results for California because:
- The use of residential air conditioning is relatively low in Indiana, and the saturations are low. Where as California has high usage of air conditioning in the summer.
- Heating use is relatively high in Indiana, while it is relatively low in California.
- The diurnal variation in temperature is low while California is very high.
- Indiana is located in western edge of the same time zone as Maine and Florida, but the sun actually comes up at an earlier time than those other two states.
- Indiana's north-south location will affect how long the days are in the summer and might very well lead to different results in different areas.
So, while the analysis is of interest to Indiana, it's conclusions may not be totally correct for California or the rest of the country. The first national study since the 1970s, was mandated by Congress and was done by the U.S. Department of Energy.
The DOE study can be downloaded at: http://www1.eere.energy.gov/ba/pba/pdfs/epact_sec_110_edst_report_to_congress_2008.pdf (PDF file, 285 kb)
The key findings in the report to Congress are:
- The total electricity savings of Extended Daylight Saving Time were about 1.3 Tera Watt-hour (TWh). This corresponds to 0.5 percent per each day of Extended Daylight Saving Time, or 0.03 percent of electricity consumption over the year. In reference, the total 2007 electricity consumption in the United States was 3,900 TWh.
- In terms of national primary energy consumption, the electricity savings translate to a reduction of 17 Trillion Btu (TBtu) over the spring and fall Extended Daylight Saving Time periods, or roughly 0.02 percent of total U.S. energy consumption during 2007 of 101,000 TBtu.
- During Extended Daylight Saving Time, electricity savings generally occurred over a three- to five-hour period in the evening with small increases in usage during the early- morning hours. On a daily percentage basis, electricity savings were slightly greater during the March (spring) extension of Extended Daylight Saving Time than the November (fall) extension. On a regional basis, some southern portions of the United States exhibited slightly smaller impacts of Extended Daylight Saving Time on energy savings compared to the northern regions, a result possibly due to a small, offsetting increase in household air conditioning usage.
- Changes in national traffic volume and motor gasoline consumption for passenger vehicles in 2007 were determined to be statistically insignificant and therefore, could not be attributed to Extended Daylight Saving Time.
But why do we have Daylight Saving Time to begin with? Who created the laws and regulations that we follow?
History of Daylight Saving Time
Daylight Saving Time is a change in the standard time of each time zone. Time zones were first used by the railroads in 1883 to standardize their schedules. According to the The Canadian Encyclopedia Plus by McClelland & Stewart Inc., Canada's "[Sir Sandford] Fleming also played a key role in the development of a worldwide system of keeping time. Trains had made obsolete the old system where major cities and regions set clocks according to local astronomical conditions. Fleming advocated the adoption of a standard or mean time and hourly variations from that according to established time zones. He was instrumental in convening an International Prime Meridian Conference in Washington in 1884 at which the system of international standard time -- still in use today -- was adopted."
In 1918, the U.S. Congress made the U.S. rail zones official under federal law and gave the responsibility to make any changes to the Interstate Commerce Commission, the only federal transportation regulatory agency at the time. When Congress created the Department of Transportation in 1966, it transferred the responsibility for the time laws to the new department.
The American law by which we turn our clock forward in the spring and back in the fall is known as the Uniform Time Act of 1966. The law does not require that anyone observe Daylight Saving Time; all the law says is that if we are going to observe Daylight Saving Time, it must be done uniformly.
Daylight Saving Time has been around for most of this century and even earlier.
Benjamin Franklin, while a minister to France, first suggested the idea in an essay titled "An Economical Project for Diminishing the Cost of Light." The essay was first published in the Journal de Paris in April 1784. But it wasn't for more than a century later that an Englishman, William Willett, suggested it again in 1907.
Willett was reportedly passing by homes where the shades were down, even though the sun was up. He wrote a pamphlet called "The Waste of Daylight" because of his observations.
Willett wanted to move the clock ahead by 80 minutes in four moves of 20 minutes each during the spring and summer months. In 1908, the British House of Commons rejected advancing the clock by one hour in the spring and back again in the autumn.
Willett's idea didn't die, and it culminated in the introduction of British Summer Time by an Act of Parliament in 1916. Clocks were put one hour ahead of Greenwich Mean Time (GMT) during the summer months.
England recognized that the nation could save energy and changed their clocks during the first World War.
In 1918, in order to conserve resources for the war effort, the U.S. Congress placed the country on Daylight Saving Time for the remainder of WW I. It was observed for seven months in 1918 and 1919. The law, however, proved so unpopular that it was later repealed.
When America went to war again, Congress reinstated Daylight Saving Time on February 9, 1942. Time in the U.S. was advanced one hour to save energy. It remained advanced one hour forward year-round until September 30, 1945.
In England, the energy saving aspects of Daylight Saving were recognized again during WWII. Clocks were changed two hours ahead of GMT during the summer, which became known as Double Summer Time. But it didn't stop with the summer. During the war, clocks remained one hour ahead of GMT though the winter.
From 1945 to 1966, there was no U.S. law about Daylight Saving Time. So, states and localities were free to observe Daylight Saving Time or not.
This, however, caused confusion -- especially for the broadcasting industry, and for trains and buses. Because of the different local customs and laws, radio and TV stations and the transportation companies had to publish new schedules every time a state or town began or ended Daylight Saving Time.
By 1966, some 100 million Americans were observing Daylight Saving Time through their own local laws and customs. Congress decided to step in end the confusion and establish one pattern across the country. The Uniform Time Act of 1966 (15 U.S. Code Section 260a) created Daylight Saving Time to begin on the last Sunday of April and to end on the last Sunday of October. Any area that wanted to be exempt from Daylight Saving Time could do so by passing a local ordinance. The law was amended in 1986 to begin Daylight Saving Time on the first Sunday in April.
Embargo Changes Daylight Saving Time
Following the 1973 Arab Oil Embargo, Congress put most of the nation on extended Daylight Saving Time for two years in hopes of saving additional energy. This experiment worked, but Congress did not continue the experiment in 1975 because of opposition -- mostly from the farming states.
In 1974, Daylight Saving Time lasted ten months and lasted for eight months in 1975, rather than the normal six months (then, May to October). The U.S. Department of Transportation -- which has jurisdiction over Daylight Saving Time in the U.S. -- studied the results of the experiment. It concluded:
- Daylight Saving Time saves energy. Based on consumption figures for 1974 and 1975, The Department of Transportation says observing Daylight Saving Time in March and April saved the equivalent in energy of 10,000 barrels of oil each day -- a total of 600,000 barrels in each of those two years. California Energy Commission studies confirm a saving of about one percent per day.
- Daylight Saving Time saves lives and prevents traffic injuries. The earlier Daylight Saving Time allowed more people to travel home from work and school in daylight, which is much safer than darkness. And except for the months of November through February, Daylight Saving Time does not increase the morning hazard for those going to school and work.
- Daylight Saving Time prevents crime. Because people get home from work and school and complete more errands and chores in daylight, Daylight Saving Time also seems to reduce people's exposure to various crimes, which are more common in darkness than in light.
The Department of Transportation estimated that 50 lives were saved and about 2,000 injuries were prevented in March and April of the study years. The department also estimated that $28 million was saved in traffic accident costs.
A study in 2007 seems to confirm that DST helps prevent accidents. The study was published in February 2007 in The B.E. Journal of Economic Analysis and Policy (Vol. 7, Issue 1, Article 11) and is titled "Short and Long Run Effects of Daylight Saving Time on Fatal Automobile Crashes."
The abstract of the study by Neeraj Sood with the RAND corporation and Arkkadipta Ghosh of the Pardee RAND Graduate School's says:
"Prior literature suggests that Daylight Saving Time (DST) can both increase the risk of automobile crashes in the short run and decrease the risk of automobile crashes in the long run.
"We use 28 years (1976-2003) of automobile crash data from the United States, and exploit a natural experiment arising from a 1986 federal law that changed the time when states switched to DST to identify the short run and long run effects of DST on automobile crashes.
"Our findings suggest that:
- DST has no significant detrimental effect on automobile crashes in the short run;
- DST significantly reduces automobile crashes in the long run with an 8-11% fall in crashes involving pedestrians, and a 6-10% fall in crashes for vehicular occupants in the weeks after the spring shift to DST."
Congress and President Reagan Change Daylight SavingTime
Daylight Saving Time was changed slightly in 1986 when President Reagan signed Public Law 99-359. It changed Daylight Saving Time from the last Sunday in April to the first Sunday in April. No change was made to the ending date of the last Sunday in October.
This was done ostensibly to conserve energy during the month of April. Adding the entire month of April is estimated to save nationwide about 300,000 barrels of oil each year.
Changed Again in 2007
The Energy Policy Act of 2005 was passed by Congress and then signed into law by President George W. Bush on August 8, 2005. Under the new law, Daylight Saving Time begins three weeks earlier than previously, on the second Sunday in March. DST is extended by one week to the first Sunday in November. The new start and stop period began in March 2007.
The original House bill would have added two full months, one in the spring and another in the fall. According to some U.S. senators, farmers complained that a two-month extension could adversely affect livestock, and airline officials said it would have complicated scheduling of international flights. So, a compromise was worked out to start DST on the second Sunday in March and end the first Sunday in November.
Enactment of the Energy Policy Act of 2005 did not alter the rights of the states and territories to choose not to observe Daylight Saving Time.
The question remains, however, whether the earlier DST will save additional energy. The California Energy Commission's Demand Analysis Office published a report titled The Effect of Early Daylight Saving Time on California Electricity Consumption: A Statistical Analysis, Commission publication # CEC-200-2007-004, in May 2007. (PDF file, 592 kilobytes).
It concludes that, "The extension of Daylight Saving Time (DST) to March 2007 had little or no effect on energy consumption in California, according to a statistical analysis. The most likely approximation is a 0.2% decrease during these three weeks. Given the natural variation in consumption, however, the margin of electricity use change associated with early DST could have been one and a half percent of increase or decrease without such effects showing up statistically. Formally, weather- and lighting-corrected savings from DST were estimated at 0.18% with a 95% confidence interval ranging from 1.5% savings to a 1.4% increase."
Seize the Daylight
A book all about DST was published in 2005 called Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time by Dr. David Prerau.
It's published by Avalon Publishing / Thunder's Mouth Press - ISBN: 1-56025-655-9.
There's also a website about the book at: www.seizethedaylight.com
Two fun quotes from the book:
"An extra yawn one morning in the springtime, an extra snooze one night in the autumn is all that we ask in return for dazzling gifts. We borrow an hour one night in April; we pay it back with golden interest five months later." -Winston Churchill
"It seems very strange . . . that in the course of the world's history so obvious an improvement should never have been adopted. . . . The next generation of Britishers would be the better for having had this extra hour of daylight in their childhood." -Sir Arthur Conan Doyle
More About TIME
Many countries observe Daylight Saving Time. But the beginning and ending dates are often different than those used in the United States.
The book, The Official Airline Guide, is one of the best sources of information about whether or not Daylight Saving Time is observed in another country.
You can find out more information about Daylight Saving Time by writing TIME, c/o Office of General Counsel, U.S. Department of Transportation, Washington, D.C. 20590.
Another Web site about DST can be found at: http://www.webexhibits.org/daylightsaving/, which is a public service of the Institute for Dynamic Educational Advancement (IDEA) by WebExhibits as a compliment to www.time.gov.
The U.S. Naval Observatory's Web site gives the current time for all time zones, and it's free. Go to: http://tycho.usno.navy.mil/cgi-bin/timer.pl.
Note, however, that with Internet traffic and delays on servers and browsers, that the correct time may be off a few seconds or more.
For the correct time of the day, you can call the Department of Transportation at 900-410-TIME. There is a charge for the call. Or check with your local phone company to see if there is a local dial up time service such as "POP-CORN."
Some phone companies also have a local number you can call for the current correct local time. Call directory assistance in your area for the number to call for the correct time.
One question people always ask about Daylight Saving Time regards the time that restaurants and bars close. In many states, liquor cannot be served after 2 a.m. But at 2 a.m. in the fall, the time switches back one hour. So, why can't they serve for that additional hour in October?
The answer: the bars do not close at 2 a.m. but actually at 1:59 a.m. So, they are already closed when the time changes from Daylight Saving Time into Standard Time.
- It is Daylight Saving (singular) Time, NOT Daylight SavingS Time. We are saving daylight, so it is singular and not plural.
- Daylight Saving Time differs in other areas of the world. Consult a good encyclopedia for additional information about DST in your own country. Or check out the "World Time Zone" at:
- There's an excellent history of time-keeping at Walk Through Time - The Evolution of Time Measurement through the Ages
- Thanks for all your e-mail! We are amazed that this page gets so much attention, usually twice a year. While we appreciate the e-mail, we can not answer a lot of your specific questions. For example, we do not have the ability to tell you whether DST was practiced on a specific date or by a specific region/state/city/town in the past. Check out microfilm or old printed copies of your local newspapers around early April and late October of the years you are interested in. They will usually have stories or reminders about setting your clock. Those papers are a good indicator. Your local libraries should be able to help you with the microfilmed or printed copies of the old newspapers.
- If you are interested in changing DST, either abolishing it or having it extended year-round....please do not contact the California Energy Commission. We have no jurisdiction over DST. Instead, contact your state's elected officials or your Congressional representatives. You can also contact the U.S. Department of Transportation in Washington, D.C.
A final note, especially in that one of my uncles was a fire chief in Connecticut, my step son is a firefighter, and one of my colleagues has a family member who is the former fire chief in Sacramento...with the change of Daylight Saving Time, it's a good time to change the batteries in your smoke detector(s). Changing the batteries twice a year will make sure that the detector(s) will be working in case there is a fire. Some detectors also need to be replaced completely about every five years or so. Also make sure you dispose of the old batteries and alarms properly. Check with your local solid waste disposal company or waste management board to find out the best way to dispose of old batteries and the alarms.
Daylight Saving Time In the United States, 1990 Through 2025
|Year||DST Begins 2 a.m. |
(First Sunday in April)
|DST Ends 2 a.m. |
(Last Sunday in October)
|1990||April 1||October 28|
|1991||April 7||October 27 |
|1992||April 5||October 25|
|1993||April 4||October 31|
|1994||April 3||October 30|
|1995||April 2||October 29|
|1996||April 7||October 27|
|1997||April 6||October 26|
|1998||April 5||October 25|
|1999||April 4||October 31|
|2000||April 2||October 29|
|2001||April 1||October 28|
|2002||April 7||October 27|
|2003||April 6||October 26|
|2004||April 4||October 31|
|2005||April 3||October 30|
|2006||April 2||October 29|
|DST Start and End date changes beginning March 2007|
|Year||DST Begins 2 a.m. |
(Second Sunday in March)
|DST Ends 2 a.m. |
(First Sunday in November)
|2007||March 11||November 4|
|2008||March 9||November 2|
|2009||March 8||November 1|
|2010||March 14||November 7|
|2011||March 13||November 6|
|2012||March 11||November 4|
|2013||March 10||November 3|
|2014||March 9||November 2|
|2015||March 8||November 1|
|2016||March 13||November 6|
|2017||March 12||November 5|
|2018||March 11||November 4|
|2019||March 10||November 3|
|2020||March 15||November 8|
|2021||March 14||November 7|
|2022||March 13||November 6|
|2023||March 12||November 5|
|2024||March 10||November 3|
|2025||March 9||November 2|
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