The Uniform Time Act of 1966 (2005 / 2007 Updates)
The first law on this page is an extension of Daylight Saving Time from "first Sunday of April through last Sunday of October" to "second Sunday of March through first Sunday of November". This provides 34 weeks of DST (238 days) every year.

The second law on this page converts time zones to "metric" - or at least to an offset from UTC instead of referring to the time zones by a reference longitude.

The second law also corrects an error that existed since at least 1966 where §264 allowed the southern area of the state to be in the third zone instead of the fourth.
PL 109-58 ENERGY POLICY ACT OF 2005
AN ACT
To ensure jobs for our future with secure, affordable, and reliable energy.

Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled,
. . .
SEC. 110. DAYLIGHT SAVINGS
  1. AMENDMENT.—Section 3(a) of the Uniform Time Act of 1966 (15 U.S.C. 260a(a)) is amended—
    1. by striking ‘‘first Sunday of April’’ and inserting ‘‘second Sunday of March’’; and
    2. by striking ‘‘last Sunday of October’’ and inserting ‘‘first Sunday of November’’.
  2. EFFECTIVE DATE.—Subsection (a) shall take effect 1 year after the date of enactment of this Act or March 1, 2007, whichever is later.
  3. REPORT TO CONGRESS.—Not later than 9 months after the effective date stated in subsection (b), the Secretary shall report to Congress on the impact of this section on energy consumption in the United States.
  4. RIGHT TO REVERT.—Congress retains the right to revert the Daylight Saving Time back to the 2005 time schedules once the Department study is complete.
. . .
Approved August 8, 2005.
(Effective March 1, 2007.)

PL 110-69 AMERICA COMPETES ACT
AN ACT
To invest in innovation through research and development,
and to improve the competitiveness of the United States.

Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled,
. . .
SEC. 3570. METRIC SYSTEM DEFINED.
  1. The metric system of measurement shall be defined as the International System of Units as established in 1960, and subsequently maintained, by the General Conference of Weights and Measures, and as interpreted or modified for the United States by the Secretary of Commerce.
  2. REPEAL OF REDUNDANT AND OBSOLETE AUTHORITY.— The Act of July 21, 1950, entitled, ‘‘An Act To redefine the units and establish the standards of electrical and photometric measurements.’’ (15 U.S.C. 223 and 224) is hereby repealed.
  3. STANDARD TIME.—Section 1 of the Act of March 19, 1918, (commonly known as the ‘‘Calder Act’’) (15 U.S.C. 261) is amended—
    1. by inserting ‘‘(a) IN GENERAL.—’’ before ‘‘For the purpose’’;
    2. by striking the second sentence and the extra period after it and inserting ‘‘Except as provided in section 3(a) of the Uniform Time Act of 1966 (15 U.S.C. 260a), the standard time of the first zone shall be Coordinated Universal Time retarded by 4 hours; that of the second zone retarded by 5 hours; that of the third zone retarded by 6 hours; that of the fourth zone retarded by 7 hours; that of the fifth zone retarded 8 hours; that of the sixth zone retarded by 9 hours; that of the seventh zone retarded by 10 hours; that of the eighth zone retarded by 11 hours; and that of the ninth zone shall be Coordinated Universal Time advanced by 10 hours.’’; and
    3. by adding at the end the following:
      4. ‘‘(b) COORDINATED UNIVERSAL TIME DEFINED.—In this section, the term ‘Coordinated Universal Time’ means the time scale maintained through the General Conference of Weights and Measures and interpreted or modified for the United States by the Secretary of Commerce in coordination with the Secretary of the Navy.’’.
  4. IDAHO TIME ZONE.—Section 3 of the Act of March 19, 1918, (commonly known as the ‘‘Calder Act’’) (15 U.S.C. 264) is amended by striking ‘‘third zone’’ and inserting ‘‘fourth zone’’.
. . .
Approved August 9, 2007.
First
Zone		 Second
Zone		 Third
Zone		 Fourth
Zone		 Fifth
Zone		 Sixth
Zone		 Seventh
Zone		 Eighth
Zone		 Ninth
Zone
UTC-04 UTC-05 UTC-06 UTC-07 UTC-08 UTC-09 UTC-10 UTC-11 UTC+10
Atlantic
standard
time		 eastern
standard
time		 central
standard
time		 mountain
standard
time		 Pacific
standard
time		 Alaska
standard
time		 Hawaii-Aleutian
standard
time		 Samoa
standard
time		 Chamorro
standard
time




SUBCHAPTER IX—STANDARD TIME

§260. Congressional declaration of policy; adoption and observance of uniform standard of time; authority of Secretary of Transportation
It is the policy of the United States to promote the adoption and observance of uniform time within the standard time zones prescribed by the Act entitled "An Act to save daylight and to provide standard time for the United States", approved March 19, 1918 (40 Stat. 450; 15 U.S.C. 261-264), as modified by the Act entitled "An Act to transfer the Panhandle and Plains section of Texas and Oklahoma to the United States standard central time zone", approved March 4,1921 (41 Stat. 1446; 15 U.S.C. 265). To this end the Secretary of Transportation is authorized and directed to foster and promote widespread and uniform adoption and observance of the same standard of time within and throughout each such standard time zone.
(Pub. L. 89–387, §2, Apr. 13, 1966, 80 Stat. 107; Pub. L. 97–449, §2(c), Jan. 12, 1983, 96 Stat. 2439.)

§260a. Advancement of time or changeover dates
(a) DURATION OF PERIOD; STATE EXEMPTION — During the period commencing at 2 o'clock antemeridian on the first Sunday of April second Sunday of March of each year and ending at 2 o'clock antemeridian on the last Sunday of October of each year, the standard time of each zone established by the Act of March 19, 1918 (15 U.S.C. 261-264), as modified by the Act of March 4, 1921 (15 U.S.C. 265), shall be advanced one hour and such time as so advanced shall for the purposes of such Act of March 19,1918, as so modified, be the standard time of such zone during such period; however, (1) any State that lies entirely within one time zone may by law exempt itself from the provisions of this subsection providing for the advancement of time, but only if that law provides that the entire State (including all political subdivisions thereof) shall observe the standard time otherwise applicable during that period, and (2) any State with parts thereof in more than one time zone may by law exempt either the entire State as provided in (1) or may exempt the entire area of the State lying within any time zone.
(b) STATE LAWS SUPERSEDED — It is hereby declared that it is the express intent of Congress by this section to supersede any and all laws of the States or political subdivisions thereof insofar as they may now or hereafter provide for advances in time or changeover dates different from those specified in this section.
(c) VIOLATIONS; ENFORCEMENT — For any violation of the provisions of this section the Secretary of Transportation or its duly authorized agent may apply to the district court of the United States for the district in wnich such violation occurs for the enforcement of this section; and such court shall have jurisdiction to enforce obedience thereto by writ of injunction or by other process, mandatory or otherwise, restraining against further violations of this section and enjoining obedience thereto.
(Pub. L. 89–387, §3, Apr. 13, 1966, 80 Stat. 107; Pub. L. 92–267, Mar. 30, 1972, 86 Stat. 116; Pub. L. 97–449, §2(c), Jan. 12, 1983, 96 Stat. 2439; July 8, 1986, 100 Stat. 764; Pub. L. 109–58, title I, §110(a), Aug. 8, 2005, 119 Stat. 615.)

§261. Zones for standard time; interstate or foreign commerce (Sec. 1)
(a) IN GENERAL.— For the purpose of establishing the standard time of the United States, the territory of the United States shall be divided into eight zones in the manner provided in this section. Except as provided in section 3(a) of the Uniform Time Act of 1966, the standard time of the first zone shall be based on the mean solar time of the sixtieth degree of longitude west from Greenwich; that of the second zone on the seventy-fifth degree; that of the third zone on the ninetieth degree; that of the fourth zone on the one hundred and fifth degree; that of the fifth zone on the one hundred and twentieth degree; that of the sixth zone on the one hundred and thirty-fifth degree; that of the seventh zone on the one hundred and fiftieth degree; that of the eighth zone on the one hundred and sixty-fifth degree; and that of the ninth zone on the one hundred and fiftieth meridian of longitude east from Greenwich. Except as provided in section 3(a) of the Uniform Time Act of 1966 (15 U.S.C. 260a), the standard time of the first zone shall be Coordinated Universal Time retarded by 4 hours; that of the second zone retarded by 5 hours; that of the third zone retarded by 6 hours; that of the fourth zone retarded by 7 hours; that of the fifth zone retarded 8 hours; that of the sixth zone retarded by 9 hours; that of the seventh zone retarded by 10 hours; that of the eighth zone retarded by 11 hours; and that of the ninth zone shall be Coordinated Universal Time advanced by 10 hours. The limits of each zone shall be defined by an order of the Secretary of Transportation, having regard for the convenience of commerce and the existing junction points and division points of common carriers engaged in interstate or foreign commerce, and any such order may be modificd from time to time. As used in this Act, the term 'interstate or foreign commerce' means commerce between a State, the District of Columbia, the Commonwealth of Puerto Rico, or any possession of the United States, and any place outside thereof.
(b) COORDINATED UNIVERSAL TIME DEFINED.— In this section, the term ‘Coordinated Universal Time’ means the time scale maintained through the General Conference of Weights and Measures and interpreted or modified for the United States by the Secretary of Commerce in coordination with the Secretary of the Navy.
(Mar. 19, 1918, ch. 24, §1, 40 Stat. 450; Pub. L. 89–387, §4(a), Apr. 13, 1966, 80 Stat. 108; Pub. L. 97–449, §2(c), Jan. 12, 1983, 96 Stat. 2439; Pub. L. 106–564, §1(a), Dec. 23, 2000, 114 Stat. 2811; Pub. L. 110–69, title III, §3013(c)(3), Aug. 9, 2007, 121 Stat. 598.)

§262. Duty to observe standard time of zones (Sec, 2)
Within the respective zones created under the authority of this Act the standard time of the zone shall insofar as practicable (as determined by the Secretary of Transportation) govern the movement of all common carriers engaged in interstate or foreign commerce. In all statutes, orders, rules, and regulations relating to the time of performance of any act by any officer or department of the United States, whether in the legislative, executive, or judicial branches of the Government, or relating to the time within which any rights shall accrue or determine, or within which an act shall or shall not be performed by any person subject to the jurisdiction of the United States, it shall be understood and intended that the time shall insofar as practicable (as determined by the Secretary of Transportation) be the United States standard time of the zone within which the act is to be performed.
(Mar. 19, 1918, ch. 24, §2, 40 Stat. 451; Pub. L. 89–387, §4(b), Apr. 13, 1966, 80 Stat. 108; Pub. L. 97–449, §2(c), Jan. 12, 1983, 96 Stat. 2439.)

§263. Designation of zone standard times (Sec. 4)
The standard time of the first zone shall be known and designated as Atlantic standard time; that of the second zone shall be known and designated as eastern standard time; that of the third zone shall be known and designated as central standard time; that of the fourth zone shall be known and designated as mountain standard time; that of the fifth zone shall be known and designated as Pacific standard time; that of the sixth zone shall be known and designated as Alaska standard time; that of the seventh zone shall be known and designated as Hawaii Aleutian standard time; that of the eighth zone shall be known and designated as Samoa standard time; and that of the ninth zone shall be known as Chamorro standard time.
(Mar. 19, 1918, ch. 24, §4, 40 Stat. 451; Pub. L. 89–387, §4(c), Apr. 13, 1966, 80 Stat. 108; Pub. L. 98–181, title II, §2003(a), Nov. 30, 1983, 97 Stat. 1297; Pub. L. 106–564, §1(a), Dec. 23, 2000, 114 Stat. 2811.)

§264. Part of Idaho in fourth zone (Sec. 3)
In the division of territory, and in the definition of the limits of each zone, as hereinbefore provided, so much of the State of Idaho as lies south of the Salmon River, traversing the State from east to west near forty-five degrees thirty minutes latitude shall be embraced in the third fourth zone: Provided, That common carriers within such portion of the State of Idaho may conduct their operations on Pacific time.
(Mar. 19, 1918, ch. 24, §3, as added Mar. 3, 1923, ch. 216, 42 Stat. 1434; amended June 24, 1948, ch. 631, §1, 62 Stat. 646; Pub. L. 110–69, title III, §3013(c)(3), Aug. 9, 2007, 121 Stat. 598.)

§265. Transfer of certain territory to standard central-time zone
That the Panhandle and Plains section of Texas and Oklahoma be, and the same are hereby, transferred to and placed within the United States standard central time zone.
The Secretary of Transportation is hereby authorized and directed to issue an order placing the western boundary line of the United States standard central time zone in so far as the same affect Texas and Oklahoma as follows:
Beginning at a point where such western boundary time zone line crosses the State boundary line between Kansas and Oklahoma; thence westerly along said State boundary line to the northwest corner of the State of Oklahoma; thence in a southerly direction along the west State boundary line of Oklahoma and the west State boundary line of Texas to the southeastern corner of the State of New Mexico; thence in a westerly direction along the State boundary line between the States of Texas and New Mexico to the Rio Grande River; thence down the Rio Grande River as the boundary line between the United States and Mexico: Provided, That the Chicago, Rock Island and Gulf Railway Company and the Chicago, Rock Island and Pacific Railway Company may use Tucumcari, New Mexico, as the point at which they change from central to mountain time and vice versa; the Colorado Southern and Fort Worth and Denver City Railway Companies may use Sixela, New Mexico, as such changing point; the Atchison, Topeka and Santa Fe Railway Company and other branches of the Santa Fe System may use Clovis, New Mexico, as such changing point, and those railways running into or through El Paso may use El Paso as such point: Provided further, That this Act shall not, except as herein provided, interfere with the adjustment of time zones as established by the Secretary of Transportation.
(Mar. 4, 1921, ch. 173, §1, 41 Stat. 1446; Pub. L. 97–449, §2(c), Jan. 12, 1983, 96 Stat. 2439.)

§266. Applicability of administrative procedure provisions (Sec. 5)
The Administrative Procedure Act (5 U.S.C. 1001-1011) shall apply to all proceedings under this Act, the Act of March 19, 1918 (15 U.S.C. 261-264), and the Act of March 4, 1921 (15 U.S.C. 265).
(Pub. L. 89–387, §5, Apr. 13, 1966, 80 Stat. 108.)

§267. "State" defined (Sec. 6)
As used in this Act, the term "State" includes the District of Columbia, the Commonwealth of Puerto Rico, Guam, the Commonwealth of the Northern Mariana Islands, or any possession of the United States.
(Pub. L. 89–387, §7, Apr. 13, 1966, 80 Stat. 109; Pub. L. 106–564, §1(a), Dec. 23, 2000, 114 Stat. 2811.)
1918-1919-1921-1923 1966-1972 1983-1986-2000 2005-2007 PROPOSED