View source for Uniform Time Act

{{Use American English|date = April 2019}}
{{Short description|United States timekeeping and daylight saving time law}}
{{Use mdy dates|date=March 2022}}

{{Infobox U.S. legislation
| shorttitle = Uniform Time Act
| othershorttitles = 
| longtitle = An Act to promote the observance of a uniform system of time throughout the United States.
| colloquialacronym = 
| nickname = Uniform Time Act of 1966
| enacted by = 89th
| effective date = April 1, 1967
| public law url = http://www.gpo.gov/fdsys/pkg/STATUTE-80/pdf/STATUTE-80-Pg107.pdf
| cite public law = 89-387
| cite statutes at large = {{usstat|80|107}}
| acts amended = [[1918 Standard Time Act|Standard Time Act of 1918]]
| acts repealed = 
| title amended = [[Title 15 of the United States Code|15 U.S.C.: Commerce and Trade]]
| sections created = {{Usc-title-chap|15|6|IX}} §§ 260–267
| sections amended = 
| leghisturl = 
| introducedin = Senate
| introducedbill = {{USbill|89|S.|1404}} by Sens. [[Gale McGee]] ([[Democratic Party (United States)|D]]–[[Wyoming|WY]]) and [[Norris Cotton]] ([[Republican Party (United States)|R]]–[[New Hampshire|NH]])
| introducedby = <!--sponsor(s)-->
| introduceddate = 
| committees = 
| passedbody1 = House
| passeddate1 = March 16, 1966
| passedvote1 = [http://www.govtrack.us/congress/votes/89-1966/h223 292–93], in lieu of H.R. 6785
| passedbody2 = 
| passedas2 = <!-- used if the second body changes the name of the legislation -->
| passeddate2 = 
| passedvote2 = 
| conferencedate = March 30, 1966
| passedbody3 = House
| passeddate3 = March 30, 1966
| passedvote3 = [http://www.govtrack.us/congress/votes/89-1966/h229 282–91]
| agreedbody3 = <!-- used when the other body agrees without going into committee -->
| agreeddate3 = <!-- used when the other body agrees without going into committee -->
| agreedvote3 = <!-- used when the other body agrees without going into committee -->
| agreedbody4 = <!-- used if agreedbody3 further amends legislation -->
| agreeddate4 = <!-- used if agreedbody3 further amends legislation -->
| agreedvote4 = <!-- used if agreedbody3 further amends legislation -->
| passedbody4 = 
| passeddate4 = 
| passedvote4 = 
| signedpresident = [[Lyndon B. Johnson]]
| signeddate = April 13, 1966
| unsignedpresident = <!-- used when passed without presidential signing -->
| unsigneddate = <!-- used when passed without presidential signing -->
| vetoedpresident = <!-- used when passed by overriding presidential veto -->
| vetoeddate = <!-- used when passed by overriding presidential veto -->
| overriddenbody1 = <!-- used when passed by overriding presidential veto -->
| overriddendate1 = <!-- used when passed by overriding presidential veto -->
| overriddenvote1 = <!-- used when passed by overriding presidential veto -->
| overriddenbody2 = <!-- used when passed by overriding presidential veto -->
| overriddendate2 = <!-- used when passed by overriding presidential veto -->
| overriddenvote2 = <!-- used when passed by overriding presidential veto -->
| amendments = 
| SCOTUS cases = 
}}
The '''Uniform Time Act of 1966''', {{USStatute|89|387|80|107|1966|04|13}}, was a [[Law of the United States]] to "promote the adoption and observance of uniform time within the standard time zones" prescribed by the [[1918 Standard Time Act|Standard Time Act of 1918]]. Its intended effect was to simplify the official pattern of where and when [[daylight saving time]] (DST) is applied within the U.S. Prior to this law, each [[U.S. state|state]] had its own scheme for when DST would begin and end, and in some cases, which parts of the state should use it.<ref>{{cite web|title=The History of Daylight Saving Time|url=http://news.nationalgeographic.com/news/2004/03/0330_040330_daylightsavings.html|archive-url=https://web.archive.org/web/20040602192225/http://news.nationalgeographic.com/news/2004/03/0330_040330_daylightsavings.html|url-status=dead|archive-date=June 2, 2004|publisher=National Geographic|access-date=June 23, 2012|author=Jennifer Vernon|date=March 31, 2006}}</ref>

==History==
The law, as originally written, required states that observe DST to begin it at 2 a.m. local time on the last Sunday in April, and to end it at 2 a.m. local time on the last Sunday in October and explicitly preempted all state laws related to daylight saving time per the [[weights and measures]] power given to Congress in Article 1, Section 8 of the [[U.S. Constitution]]. In 1972, the act was amended to allow states with more than one timezone to exempt only one timezone from DST, in addition to exempting the whole state.<ref name="amendment-1972">An Act to amend the Uniform Time Act to allow an option in the adoption of advanced time in certain cases. {{uspl|92|267}}</ref> The law was later amended again in 1986 to move the uniform start date for DST to the first Sunday in April (effective 1987). The latest amendment, part of the [[Energy Policy Act of 2005]], extends DST by four or five weeks by moving the uniform start date for DST to the second Sunday in March and the end date to the first Sunday in November (effective 2007). The [[United States Department of Energy|Department of Energy]] was required to report to Congress the impact of the DST extension by December 1, 2007 (nine months after the statute took effect). The report, released in October 2008, reported a nationwide electricity savings of 0.03% for the year of 2007.<ref>Belzer, David B. (October 2008). Impact of Extended Daylight Saving Time on National Energy Consumption. U.S. Department of Energy. {{cite web |url=http://www1.eere.energy.gov/analysis/pdfs/epact_sec_110_edst_report_to_congress_2008.pdf |title=Archived copy |access-date=October 21, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130518104926/http://www1.eere.energy.gov/analysis/pdfs/epact_sec_110_edst_report_to_congress_2008.pdf |archive-date=May 18, 2013 }}</ref>

===Specifications===
The law does not require that all states observe DST. Individual states may exempt themselves from DST and observe standard time year-round by passing a state law, provided:
* if the state lies entirely within a [[time zone]], that the exemption apply statewide, or
* if the state is divided by a time zone boundary, that the exemption apply statewide or to the entire part of the state on one side of the boundary.

==Non-observers==
[[File:AZNMUT DST observance.png|left|thumb|162x162px|The observance of daylight saving in Arizona varies as shown]]
The state of [[Hawaii]] has never observed daylight saving, even during World War II when "War Time" was observed by other states as an energy saving measure. 

The territories of the [[Northern Mariana Islands]], [[Puerto Rico]], [[American Samoa]], [[Guam]], and [[United States Virgin Islands|U.S. Virgin Islands]] also do not observe Daylight Saving Time.<ref>{{cite web|title=The History of Daylight Saving Time|url=http://news.nationalgeographic.com/news/2004/03/0330_040330_daylightsavings.html|archive-url=https://web.archive.org/web/20040602192225/http://news.nationalgeographic.com/news/2004/03/0330_040330_daylightsavings.html|url-status=dead|archive-date=June 2, 2004|publisher=National Geographic|access-date=June 23, 2012|author=Jennifer Vernon|date=March 31, 2006}}</ref>

Observance of daylight saving varied by county in [[Indiana]], which is divided by the Eastern/Central time zone boundary, until April 2, 2006, when the entire state once again observed DST, a first since Congress repealed the Standard Time Act of 1918.<ref>{{cite web|url=https://www.indystar.com/story/news/2019/03/08/why-indiana-observes-daylight-saving-time-statewide/3092875002/|publisher=IndyStar|access-date=November 24, 2020|date=March 8, 2019|author=Justin L. Mack|title=Looking back at Indiana's complicated relationship with time: Why Indiana observes daylight saving time}}</ref>

Arizona has not observed daylight saving since the year following the enactment of the Uniform Time Act of 1966. [[Native Americans in the United States|Native American]] nations within Arizona may choose. The [[Navajo Nation]] has chosen to use daylight saving throughout its territory, which includes parts of [[New Mexico]] and [[Utah]] where daylight saving is observed. The [[Hopi]] Nation, with territory surrounded entirely by the Arizona portion of the Navajo Nation, has chosen not to observe daylight saving.

== See also ==
* [[1918 Standard Time Act]]
*[[Time in Indiana]]
*[[Time in Arizona]]
* [[Sunshine Protection Act]]

==References==
{{reflist}}

{{Time in the United States}}
{{Lyndon B. Johnson}}

[[Category:1966 in American law]]
[[Category:89th United States Congress]]
[[Category:United States federal energy legislation]]
[[Category:Daylight saving time in the United States]]