Daylight saving time in the United States

Daylight saving time in the United States
Ohio Clock in the U.S. Capitol being turned forward for the country's first daylight saving time in 1918

Daylight saving time in the United States was first observed in 1918. Most areas of the United States currently observe daylight saving time, with the exceptions being the states of Arizona and Hawaii along with the territories of Puerto Rico, American Samoa, Guam, and the Northern Mariana Islands.

From 1987 to 2006, daylight saving time in the United States began on the first Sunday of April and ended on the last Sunday of October. The time was adjusted at 2:00 AM (0200) local time (as it still is done now).

Since 2007, daylight saving time starts on the second Sunday of March and ends on the first Sunday of November, with all time changes taking place at 2:00 AM (0200) local time. In 2011, daylight saving time began on March 13 and ended on November 6; in 2012, it will begin on March 11 and end on November 4.[1]


History of DST in the United States

1918 to 1987

During World War I, in an effort to conserve fuel, Germany began observing DST on May 1, 1916. As the war progressed, the rest of Europe adopted DST. The plan was not formally adopted in the United States until the Standard Time Act of March 19, 1918. It established both standard time zones and set summer DST to begin on March 31, 1918. The idea was unpopular, however, and Congress abolished DST after the war, overriding President Woodrow Wilson's veto.[citation needed] DST became a local option and was observed in some states until World War II, when President Franklin Roosevelt instituted year-round DST, called "War Time", on February 9, 1942. It lasted until the last Sunday in September 1945. The next year, many states and localities adopted summer DST.[2]

From 1945 to 1966, there was no federal law regarding daylight saving time, so states and localities were free to choose whether to observe it, and could choose when it began and ended. By 1962, the transportation industry found the lack of nationwide consistency in time observance confusing enough to push for federal regulation. This drive resulted in the Uniform Time Act of 1966 (P.L. 89-387). The act mandated standard time within the established time zones and provided for advanced time: clocks would be advanced one hour beginning at 2:00 a.m. on the last Sunday in April and turned back one hour at 2:00 a.m. on the last Sunday in October. States were allowed to exempt themselves from DST as long as the entire state did so. If a state chose to observe DST, the time changes were required to begin and end on the established dates. In 1968, Arizona became the first state to exempt itself from DST. In 1972, the act was amended (P.L. 92-267), allowing those states split between time zones to exempt either the entire state or that part of the state lying within a different time zone. The newly created Department of Transportation (DOT) was given the power to enforce the law. Currently, the following states and territories do not observe DST: Arizona, Hawaii, American Samoa, Puerto Rico, and the Virgin Islands.[2]

During the 1973 oil embargo by the Organization of Petroleum Exporting Countries (OPEC), in an effort to conserve fuel Congress enacted a trial period of year-round DST (P.L. 93-182), beginning January 6, 1974, and ending April 27, 1975. From the beginning, the trial was hotly debated. Those in favor pointed to the benefits of increased daylight hours in the winter evening: more time for recreation, reduced lighting and heating demands, reduced crime, and reduced automobile accidents. The opposition was concerned about children leaving for school in the dark. The act was amended in October 1974 (P.L. 93-434) to return to standard time for the period beginning October 27, 1974, and ending February 23, 1975, when DST resumed. When the trial ended in 1975, the country returned to observing summer DST (with the aforementioned exceptions).[2]

DOT, charged with evaluating the plan of extending DST into March, reported in 1975 that "modest overall benefits might be realized by a shift from the historic six-month DST (May through October) in areas of energy conservation, overall traffic safety and reduced violent crime." However, DOT also reported that these benefits were minimal and difficult to distinguish from seasonal variations and fluctuations in energy prices.[2]

Congress then asked the National Bureau of Standards (NBS) to evaluate the DOT report. In an April 1976 report to Congress, Review and Technical Evaluation of the DOT Daylight Saving Time Study, NBS found no significant energy savings or differences in traffic fatalities. It did find statistically significant evidence of increased fatalities among school-age children in the mornings during the four-month period January–April 1974 as compared with the same period (non-DST) of 1973. NBS stated that it was impossible to determine, what if any of this increase was due to DST. When this same data was compared between 1973 and 1974 for the individual months of March and April, no significant difference was found for fatalities among school-age children in the mornings.[2]

In 1986, the 99th Congress enacted P.L. 99-359, which amended the Uniform Time Act, by changing the beginning of DST to the first Sunday in April and having the end remain the last Sunday in October.[2]

Changing an Area's Time Zone. Under the Standard Time Act of 1918, as amended by the Uniform Time Act of 1966, moving a state or an area within a state from one time zone to another requires a regulation issued by the Department of Transportation (DOT). The governor or state legislature makes the request for a state or any part of the state; the highest elected officials in the county may make a request for that county. The standard in the statute for such decisions is the convenience of commerce in that area. The convenience of commerce is defined broadly to consider such circumstances as the shipment of goods within the community; the origin of television and radio broadcasts; the areas where most residents work, attend school, worship, or receive health care; the location of airports, railway, and bus stations; and the major elements of the community's economy.[2]

After receiving a request DOT will then determine whether it meets the minimum statutory criteria before issuing a notice of proposed rulemaking, which will solicit public comment and schedule a public hearing. Usually the hearing is held in the area requesting the change so that all affected parties can be represented. After the close of the comment period, the comments are reviewed and appropriate final action taken. If the Secretary agrees that the statutory requirement has been met, the change is instituted, usually at the next changeover to or from DST.[2]

1987 to 2006

Moving an Area On or Off DST. Under the Uniform Time Act, moving an area on or off DST is accomplished through legal action at the state level. Some states require legislation while others require executive action such as a governor's executive order. Information on procedures required in a specific state may be obtained from that state's legislature or governor's office. Although it may exempt itself, if a state decides to observe DST, the dates of observance must comply with federal legislation.[2]

The schedule through 2006 in the United States was that DST began on the first Sunday in April (April 2, 2006), and changed back to standard time on the last Sunday in October (October 29, 2006). The time is adjusted at 2:00 AM (0200) local time.

2007 to the present

By the Energy Policy Act of 2005, daylight saving time (DST) was extended in the United States in 2007. DST starts on the second Sunday of March and it ends on the first Sunday of November. These changes result in a DST period that is four weeks longer than in previous years.[3] In 2008 daylight saving time ended at 2:00 AM (0200) on Sunday, November 2, and in 2009 it began at 2:00 AM (0200) on Sunday, March 8.[4] Wyoming Senator Michael Enzi and Michigan Representative Fred Upton advocated the extension from October into November especially to allow children to go trick-or-treating in more daylight.[5]

The following table lists the dates of DST under the current law through 2025, barring any further adjustments to the law:

Year Date DST Begins Date DST Ends
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 8 November 1
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

Under Section 110 of the Act, the U.S. Department of Energy was required to study the impact of the 2007 DST extension no later than nine months after the change took effect. The report, released in October 2008, reported a nationwide electricity savings of 0.03% for the year of 2007.[6]

An October 2008 study conducted by the University of California at Santa Barbara for the National Bureau of Economic Research found that the 2006 DST adoption in Indiana increased energy consumption in Indiana by an average of 1%. Although energy consumption for lighting dropped as a result of the DST adoption, consumption for heating and cooling increased by 2 to 4%. The cost to the average Indiana household of the DST adoption was determined to be $3.29 per year, for an aggregate cost of $1.7 million to $5.5 million per year.[7]

Local observance of DST


Alaska observes DST although there is a statewide move to abolish it. As of July 24, 2006 (2006 -07-24), Alaska's lieutenant governor Loren Leman approved a petition to collect signatures to put the initiative measure on the ballot by 2008. Due to its high latitude, Alaska has nearly round-the-clock daylight during summer and DST is seen by some Alaskans as unnecessary and a nuisance.

Another issue is that the Alaskan mainland's single time zone is too wide and there is a large disparity between civil time and solar time, with solar noon occurring as late as 3:00 PM (1500) by the clock in places like Nome. Others argue that ending daylight saving time will place Alaska as much as five hours from Eastern Daylight Time, making coordination of travel and phone conversations more difficult.


Arizona observed DST in 1967 under the Uniform Time Act because the state legislature did not enact an exemption statute that year. In March 1968, the DST exemption statute was enacted and the state of Arizona has not observed DST since 1967 (however, the large Navajo Indian Reservation, which extends from Arizona into two adjacent states, does,[8] but the Hopi Reservation, which is completely contained within both the Navajo reservation and the state of Arizona, does not). This is in large part due to energy conservation: Phoenix and Tucson are hotter than any other large U.S. metropolitan area during the summer, resulting in more power usage from air conditioning units and evaporative coolers in homes and businesses.[citation needed][disputed ] An extra hour of sunlight while people are active would cause people to run their cooling systems longer, thereby using more energy.[9] Local residents[who?] remember the summer of 1967, the one year DST was observed. The State Senate Majority leader at the time[citation needed] owned drive-in movie theaters and was nearly bankrupted by the practice. Movies could not start until 10:00 PM (2200) at the height of summer: well past normal hours for most Arizona residents. There has never been any serious consideration of reversing the exemption.[citation needed]


At the end of the 20th century, Colorado Springs Gazette columnist Ralph Routon wrote a series of columns supporting the idea of placing all of Colorado on year-round DST in order to save state residents the "aggravation of resetting their clocks every six months."[10] The idea gathered noticeable popular support in Colorado Springs, and the attention of the state's larger newspapers,[11] but when then state Senator MaryAnne Tebedo attempted to present the idea to the state legislature, her research uncovered federal laws forbidding the state-initiated extension of daylight saving time. Still determined to relieve Coloradans of the need to change their clocks, Tebedo introduced the only bill legally permitted to her: a proposal to exempt the state of Colorado from DST. The bill failed to escape committee during the 2000 legislative session.[12]


Daylight time is less useful in Florida than in many other states because of its southern location. There is opposition to DST in Florida.[13] In March 2008, Florida state senator Bill Posey introduced a bill in the Florida legislature to abolish daylight time in the state and keep Florida on year-round standard time.[14] Because Florida is in two time zones, the Florida legislature has the option of returning all or part of the state to standard time along time zone boundaries.[dated info]


Because of Hawaii's tropical latitude, there is not a large variation in daylight length between winter and summer. Advancing the clock in Hawaii would make sunrise times close to 7:00 A.M. even in June.[15]

Most of the inhabited islands are located close to the west end of the Hawaii-Aleutian time zone, but Oahu, Kauai and Niihau are located more than 7 degrees west of the Hawaii-Aleutian time zone's meridian and should, theoretically, be located in the next time zone to the west.

Hawaii did experiment with DST for three weeks between April 30, 1933 and May 21, 1933; there is no known official record as to why it was implemented or discontinued.[16][unreliable source?] Hawaii has never observed daylight saving time under the Uniform Time Act, having opted out of the Act's provisions in 1967.[17]


From 1970 until 2006, most of Indiana in the Eastern Time Zone did not observe daylight saving time, but the entire state started to do so in April 2006 after eight counties in western Indiana were shifted from the Eastern Time Zone to the Central Time Zone.[18] One of the goals for observing DST was to get more Indiana counties observing the same timezone; formerly, 77 counties observed EST, 5 observed EST/EDT (the EDT usage being unofficial only), and 10 observed CST/CDT. At present Indiana has 12 counties observing Central Daylight Time while the remaining 80 counties observe Eastern Daylight Time.


In 1967 the Michigan Legislature adopted a statute, Act 6 of the Public Acts of 1967, exempting the state from the observance of DST. The exemption statute was suspended on June 14, 1967, however, when the referendum was invoked. From June 14, 1967, until the last Sunday in October, 1967, Michigan observed DST, and did so in 1968 as well. The exemption statute was submitted to the voters at the General Election held in November, 1968, and, in a very close vote, the exemption statute was sustained. As a result, Michigan did not observe DST in 1969, 1970, 1971, or 1972. In November, 1972, an initiative measure, repealing the exemption statute, was approved by the voters. Michigan has observed DST in 1973 and all subsequent years.


In 2005, Nevada Assembly Bill 18 would have exempted Nevada from daylight saving time. The bill's author, Assemblyman Bob McCleary, D-North Las Vegas, argued that because of southern Nevada's desert climate, it would reduce power usage during the peak summer months by reducing the time that people would operate their home air conditioners. The result of not observing DST, however, would place the state in an odd time configuration relative to neighboring states. Because it is on the eastern edge of the Pacific Time Zone, Nevada (PST) would be two hours behind Utah (MDT), its eastern neighbor, and one hour behind California (PDT), its western neighbor. In the summer, it would therefore be the same time in Nevada (PST) as it would be in the majority of Alaska (AKDT). The bill died without a vote.[19]

Other U.S. locations

All U.S. insular territories with civilian government (American Samoa, Guam, Northern Mariana Islands, Puerto Rico, and the Virgin Islands), lie in the tropics and do not observe DST.

While neighboring Samoa began observing DST in September 2010, the smaller American Samoa cannot legally follow because of the DST observation period mandated by the Uniform Time Act. This period is actually "wintertime" in this Southern Hemisphere territory.

Time zones

Many computer operating systems (such as Linux, UNIX, Mac OS X, and Microsoft Windows) and programming languages (such as Java, perl, and most shell languages) allow a local time zone setting in the format of (Standard Time Zone abbreviation)(UTC hour difference)(Daylight Saving Time Zone abbreviation). This allows programs and programming languages that must do calculations based on local time to more easily calculate differences between local time and UTC, as well as knowing whether calculations should be changed during Daylight Saving Time. For example, a time zone setting of EST5EDT indicates that local time on the computer is 5 hours behind UTC and should be adjusted for Daylight Saving Time.

Time Zone Standard Time Daylight Saving Time
Eastern Time Zone EST (UTC-5) EDT(UTC-4)
Central Time Zone CST (UTC-6) CDT (UTC-5)
Mountain Time Zone MST (UTC-7) MDT (UTC-6)
Pacific Time Zone PST (UTC-8) PDT (UTC-7)
Alaska Time Zone AKST (UTC-9) AKDT (UTC-8)
Hawaii-Aleutian Time Zone HAST (UTC-10) HADT (UTC-9)
Aleutian Islands only

See also

General topic

Official Civil Time Distribution

Quasi-governmental time distribution systems

  • CDMA cellphone stratum 2 time distribution system
  • GNSS global navigation stratum 1 time distribution system


  1. ^ "Daylight Time". United States Naval Observatory. Retrieved 2011-11-06. 
  2. ^ a b c d e f g h i Source: CRS Report to Congress [1] s:Congressional Research Service Report RS22284 Daylight Saving Time
  3. ^ Douma, Michael (2008). "Daylight Saving Time - When do we change our clocks?". Institute for Dynamic Educational Advancement. Retrieved 2008-03-08. 
  4. ^ "Time and Frequency Division FAQ". National Institute of Standards and Technology. 
  5. ^ Ast, William F. III (2009-10-30). "Time shifts backward early Sunday morning". The Herald-Palladium. Retrieved 2009-10-30. 
  6. ^ Belzer, David B. (October 2008). Impact of Extended Daylight Saving Time on National Energy Consumption. U.S. Department of Energy. 
  7. ^ Lotchen, Matthew (October 2008). Does Daylight Saving Time Save Energy? Evidence from a Natural Experiment in Indiana. National Bureau of Economic Research. 
  8. ^ "Navajo Nation". Retrieved 2010-06-25. 
  9. ^ Shimoda, Yoshiyuki; Asahi, Takahiro; Taniguchi, Ayako; Mizuno, Minoru (2007). "Evaluation of city-scale impact of residential energy conservation measures using the detailed end-use simulation model". Energy 32 (9): 1617. doi:10.1016/ 
  10. ^ Routon mentions in his original column, "Let's Make Daylight Time Year-Round" Gazette, The (Colorado Springs), 23 October 1999, several other beneficial effects, at least to himself
  11. ^ Said attention being negative, as Ed Quillen savaged the plan in his article The Plot to Eliminate the Mountain Time Zone, Denver Post, 7 November 1999,
  12. ^ "Year-round Daylight Time is Not an Option" Gazette, The (Colorado Springs), 29 January, 2000: Routon mentions Tebedo's intent to introduce the bill
  13. ^
  14. ^ [2][dead link]
  15. ^ "and". Retrieved 2010-06-25. 
  16. ^ "Has Hawaii ever been on daylight saving time, even for a very short time? If yes, when?". Hawaii NewsList.  The page cites The American Atlas, 5th ed., by Thomas G. Shanks. It is also worth noting that until circa 1946 Hawaii Standard Time was UTC-10:30.
  17. ^ "Hawaii Revised Statutes, §1-31". Retrieved 2010-06-25. 
  18. ^ Standard Time Zone Boundary in the State of Indiana (a 139 KB PDF file)
  19. ^ Las Vegas Review-Journal (Ed Vogel) Assembly panel likely to let daylight saving time bill die 05 April 2005

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