Daylight Time

Starting in 2007, daylight time begins in the United States on the second Sunday in March and ends on the first Sunday in November. On the second Sunday in March, clocks are set ahead one hour at 2:00 a.m. local standard time, which becomes 3:00 a.m. local daylight time. On the first Sunday in November, clocks are set back one hour at 2:00 a.m. local daylight time, which becomes 1:00 a.m. local standard time. These dates were established by Congress in the Energy Policy Act of 2005, Pub. L. no. 109-58, 119 Stat 594 (2005).

Not all places in the U.S. observe daylight time. In particular, Hawaii and most of Arizona do not use it. Indiana adopted its use beginning in 2006.

Year	Begin	End
2006	April 2	October 29
2007 *	March 11	November 4
2008	March 9	November 2
2009	March 8	November 1
2010	March 14	November 7
2011	March 13	November 6
2012	March 11	November 4
2013	March 10	November 3
2014	March 9	November 2
2015	March 8	November 1

* New law went into effect.

Many countries observe some form of "summer time" and the dates when the changes are made are various and not determined by any international agreements.

Daylight time and time zones in the U.S. are defined in the U.S. Code, Title 15, Chapter 6, Subchapter IX - Standard Time.

History of Daylight Time in the U.S.

Although standard time in time zones was instituted in the U.S. and Canada by the railroads in 1883, 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 Daylight saving time was repealed in 1919, but standard time in time zones remained in law.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 time became a local matter. It was re-established nationally early in World War II, and was continuously observed from 9 February 1942 to 30 September 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 time in the U.S. but allowed for local exemptions from its observance. The act provided that daylight 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.

During the "energy crisis" years, Congress enacted earlier starting dates for daylight time. In 1974, daylight time began on 6 January and in 1975 it began on 23 February. After those two years the starting date reverted back to the last Sunday in April. In 1986, a law was passed that shifted the starting date of daylight time to the first Sunday in April, beginning in 1987. The ending date of daylight time was not subject to such changes, and remained the last Sunday in October. The Energy Policy Act of 2005 changed both the starting and ending dates. Beginning in 2007, daylight time starts on the second Sunday in March and ends on the first Sunday in November.

For a very readable account of the history of standard and daylight time in the U.S., see

• Ian R. Bartky and Elizabeth Harrison: "Standard and Daylight-saving Time", Scientific American, May 1979 (Vol. 240, No. 5), pp. 46-53.

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and a wonderful map about all daylight-times all over the world you might find here

my rule of thumb (after years of changing my clocks the wrong way round):

spring ahead, 

fall back

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Daylight Saving Time Around the World 2011

• USA & Canada:     March 13   -  November 6
  
• European Union:  March 27   -  October 30

source: http://www.timeanddate.com/time/dst/2011.html

Daylight Saving Time

U.S. Daylight Saving Time Schedule

2004: April 4 - October 31

2005: April 3 - October 30

2006: April 2 - October 29

New Federal Law In Effect

2007: March 11 - Nov. 4

2008: March 9 - Nov. 2

2009: March 8 - Nov. 1

2010: March 14 - Nov. 7

2011: March 13 - Nov. 6

At 2 a.m. on March 9, 2008, groggy Americans will turn their clocks forward one hour, marking the beginning of Daylight Saving Time (DST).

The federal law that established "daylight time" in the United States does not require any area to observe daylight saving time. But if a state chooses to observe DST, it must follow the starting and ending dates set by the law. From 1986 to 2006 this was the first Sunday in April to the last Sunday in October, but starting in 2007, it is observed from the second Sunday in March to the first Sunday in November, adding about a month to daylight saving time. (See: New Federal Law.)

No More Sunlight in Arizona and Hawaii
Arizona (with the exception of the Navajo Nation) and Hawaii and the territories of Puerto Rico, Virgin Islands, Guam, and American Samoa are the only places in the U.S. that do not observe DST but instead stay on "standard time" all year long. And if you've spent any time in the sweltering summer sun in those regions you can understand why residents don't need another hour of sunlight.

The Dawning of DST in Indiana
Until April 2005, when Indiana passed a law agreeing to observe daylight saving time, the Hoosier state had its own unique and complex time system. Not only is the state split between two time zones, but until recently, only some parts of the state observed daylight saving time while the majority did not.
Under the old system, 77 of the state's 92 counties were in the Eastern Time Zone but did not change to daylight time in April. Instead they remained on standard time all year. That is, except for two counties near Cincinnati, Ohio, and Louisville, Ky., which did use daylight time.
But the counties in the northwest corner of the state (near Chicago) and the southwestern tip (near Evansville), which are in the Central Time Zone, used both standard and daylight time.
The battle between the old system and DST was contentious and hard-won—bills proposing DST had failed more than two dozen times until finally squeaking through the state legislature in April 2005. As of April 2, 2006, the entire state of Indiana joined 47 other states in observing Daylight Saving Time. But it wasn't quite as simple and straightforward as all that—telling time in Indiana remains something of a bewildering experience: eighteen counties now observed Central Daylight Time and the remaining 74 counties of Indiana observe Eastern Daylight Time.

New Federal Law—Springing Forward in March, Back in November
Months after Indiana passed the law that got it in step with the rest of the country, the federal government announced a major change in Daylight Saving Time. In Aug. 2005, Congress passed an energy bill that included extending Daylight Saving Time by about a month. As of 2007, DST starts the second Sunday of March and ends on the first Sunday of November.

Comparisons Around the World
More than one billion people in about 70 countries around the world observe DST in some form. Here are interesting facts about some of these countries:
Most of Canada uses Daylight Saving Time. Some exceptions include the majority of Saskatchewan and parts of northeastern British Columbia. In the fall of 2005, Manitoba and Ontario announced that like the United States, they would extend daylight time starting in 2007. The attorney general of Ontario commented that "it is important to maintain Ontario's competitive advantage by coordinating time changes with our major trading partner, and harmonizing our financial, industrial, transportation, and communications links." Other provinces have indicated that they may also follow suit.
It wasn't until 1996 that our NAFTA neighbors in Mexico adopted DST. Now all three Mexican time zones are on the same schedule as the United States.
Also in 1996, members of the European Union agreed to observe a "summer-time period" from the last Sunday in March to the last Sunday in October.
Most countries near the equator don't deviate from standard time.
In the Southern Hemisphere, where summer arrives in what we in the Northern Hemisphere consider the winter months, DST is observed from late October to late March.
Three large regions in Australia do not participate in DST. Western Australia, the Northern Territory, and Queensland stay on standard time all year. The remaining south-central and southeastern sections of the continent (which is where Sydney and Melbourne are found) make the switch. This results in both vertical and horizontal time zones Down Under during the summer months.
China, which spans five time zones, is always eight hours ahead of Greenwich Mean Time and it does not observe DST.
In Japan, DST was implemented after World War II by the U.S. occupation. In 1952 it was abandoned because of strong opposition by Japanese farmers.