War Time (WW II)
During World War II the United States followed permanent DST as an effort to save energy. The law was a simple advancement of each time zone by one hour.

The law was set to expire at the last Sunday of the seventh month after the end of the war or on an earlier date agreed by congress. Congress chose the latter path, ending DST before the winter of 1945.

tzdata reports the changes as follows:
# Rule NAME FROM   TO     -   IN  ON        AT       SAVE   LETTER/S
Rule   US   1942   only   -   Feb 9         2:00     1:00   W # War
Rule   US   1945   only   -   Aug 14        23:00u   1:00   P # Peace
Rule   US   1945   only   -   Sep 30        2:00     0      S

56 Stat. 9 - PL 77-403
AN ACT
To promote the national security and defense by establishing daylight saving time.

Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That beginning at 2 o’clock antemeridian of the twentieth day after the date of enactment of this Act, the standard time of each zone established pursuant to the Act entitled “An Act to save daylight and to provide standard time for the United States”, approved March 19, 1918, as amended, shall be advanced one hour.

Sec . 2. This Act shall cease to be in effect six months after the termination of the present war or at such earlier date as the Congress shall by concurrent resolution designate, and at 2 o’clock antemeridian of the last Sunday in the calendar month following the calendar month during which this Act ceases to be in effect the standard time of each zone shall be returned to the mean astronomical time of the degree of longitude governing the standard time for such zone as provided in such Act of March 19, 1918, as amended.

Approved, January 20, 1942.
Effective February 9, 1942. (Monday)
May 8, 1945 (V-E Day): War officially ended in Europe
August 14–15, 1945 (V-J Day): Japan announced its intent to surrender
Broadcasters began to informally announce time as "Peace Time".
September 2, 1945: Formal surrender documents signed
December 31, 1946: Official Cessation of Hostilities Proclamation
April 28, 1952: Treaty of Peace with Japan


Six months after V-E day would have been November 8th, triggering an end of "War Time" the last Sunday of December.
Six months after V-J day would have been February 14th, triggering an end of "War Time" the last Sunday of March.
Six months after Japan's surrender would have been March 2nd, triggering an end of "War Time" the last Sunday of April.

59 Stat. 537 - PL 79-187
AN ACT
To provide for termination of daylight saving time.

Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That notwithstanding the provisions of the Act of January 20, 1942, entitled "An Act to promote the national security and defense by establishing daylight saving time", at 2 o'clock antemeridian on Sunday, September 30, 1945, the standard time of each zone established pursuant to the Act entitled "An Act to save daylight and to provide standard time for the United States", approved March 19, 1918, as amended, shall be returned to the mean astronomical time of the degree of longitude governing the standard time for such zone as provided in such Act of March 19, 1918, as amended.

Approved, September 25, 1945.
Effective September 30, 1945. (Last Sunday)
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