During late Winter we move our clocks one hour ahead and "lose" an hour during the night and each Fall we move our clocks back one hour and "gain" an extra hour. The phrase "Spring forward, Fall back" helps people remember how
Daylight Saving Time affects their clocks. At 2 a.m. on the second
Sunday in March, we set our clocks forward one hour ahead of Standard
Time ("Spring forward," even though Spring doesn't begin until late
March, several weeks after the start of Daylight Saving Time). We "Fall
back" at 2 a.m. on the first Sunday in November by setting our clock
back one hour and thus returning to Standard Time.
The change to Daylight Saving Time ostensibly allows us to use less
energy in lighting our homes by taking advantage of the longer and later
daylight hours. During the eight-month period of Daylight Saving Time,
the names of time in each of the time zones in the U.S. (map)
change as well. Eastern Standard Time (EST) becomes Eastern Daylight
Time, Central Standard Time (CST) becomes Central Daylight Time (CDT),
Mountain Standard Time (MST) becomes Mountain Daylight Time (MDT),
Pacific Standard Time becomes Pacific Daylight Time (PDT), and so forth.
History of Daylight Saving Time
Daylight Saving Time was instituted in the United States during World War I
in order to save energy for war production by taking advantage of the
later hours of daylight between April and October. During World War II
the federal government again required the states to observe the time
change. Between the wars and after World War II, states and communities chose whether or not to observe Daylight Saving Time. In 1966, Congress passed the Uniform Time Act, which standardized the length of Daylight Saving Time.
Daylight Saving Time is four weeks longer since 2007 due to the
passage of the Energy Policy Act in 2005. The Act extended Daylight
Saving Time by four weeks from the second Sunday of March to the first
Sunday of November, with the hope that it would save 10,000 barrels of
oil each day through reduced use of power by businesses during daylight
hours. Unfortunately, it is exceedingly difficult to determine energy
savings from Daylight Saving Time and based on a variety of factors, it
is possible that little or no energy is saved by Daylight Saving Time.
Arizona(except some Indian Reservations),Hawaii, Puerto Rico, the U.S. Virgin Islands, and America Samoa have chosen not to observe Daylight Saving Time. This choice does make
sense for the areas closer to the equator because the days are more
consistent in length throughout the year.
Daylight Saving Time Around the World
Other parts of the world
observe Daylight Saving Time as well. While European nations have been
taking advantage of the time change for decades, in 1996 the European Union
(EU) standardized a EU-wide European Summer Time. This EU version of Daylight Saving Time runs from the last Sunday in March through the last Sunday in October.
In the southern hemisphere
where Summer comes in December, Daylight Saving Time is observed from
October to March. Equatorial and tropical countries (lower latitudes)
don't observe Daylight Saving Time since the daylight hours are similar
during every season; so there's no advantage to moving clocks forward
during the Summer.
Kyrgyzstan and Iceland are the only countries that observe year-round Daylight Saving Time.