the United States, daylight saving time begins on the first Sunday in
April and ends on the last Sunday in October. On the first Sunday in
April, clocks are set ahead one hour (spring ahead) at 2:00 a.m. local
standard time, which becomes 3:00 a.m. local daylight saving time. On
the last Sunday in October, clocks are set back one hour at 2:00 a.m.
local daylight saving time, which becomes 1:00 a.m. local standard time.
all places in the U.S. observe daylight saving time. In particular,
Arizona, Hawaii, and most of Indiana do not use it.
other countries observe some form of "summer time", but they
do not necessarily change their clocks on the same dates as the U.S.
saving time and time zones in the U.S. are defined in the U.S. Code,
Title 15, Chapter 6, Subchapter IX -
History of Daylight Time in the US:
time in time zones was instituted in the U.S. and Canada by the
railroads in 1883, but it was not established in U.S. law until the Act
of March 19, 1918 (sometimes called the Standard Time Act). The act also
established daylight saving time, a contentious idea then. Daylight
saving time was repealed in 1919, but standard time in time zones
remained in law. Daylight saving time became a local matter. It was
re-established nationally during the early part World War II, and was
continuously observed from February 9, 1942 to September 20, 1945. After
the war its use varied among states and localities. The Uniform Time Act
of 1966 provided standardization in the dates of beginning and end of
daylight saving time in the U.S. but allowed for local exemptions from
its observance. The act provided that daylight saving time begin on the
last Sunday in April and end on the last Sunday in October, with the
changeover to occur at 2 a.m. local time.
the "energy crisis" years, Congress enacted earlier starting
dates for daylight saving time. In 1974, daylight saving time began on