daylight savings time 2011
During World War I, in an effort to conserve fuel, Germany began observing DST on May 1, 1916. [...] Daylight saving time in the United States was first observed in 1918. [1]
Daylight Saving Time (or summertime as it is called in many countries) is a way of getting more light out of the day by advancing clocks by one hour during the summer. [2]
Note that the list might not be final - countries, territories and states sometimes make adjustments that are announced just days or weeks ahead of the change. [3]
The conception of DST was mainly credited to an English builder, William Willett in 1905, when he presented the idea to advance the clock during the summer months. [2]
Most areas of the United States currently observe daylight saving time, with the exceptions being the states of Arizona and Hawaii along with the territories of Puerto Rico, American Samoa, Guam, and the Northern Mariana Islands. [...] Another issue is that the Alaskan mainland’s single time zone is too wide and there is a large disparity between civil time and solar time, with solar noon occurring as late as 3:00 PM (1500) by the clock in places like Nome. [1]
Daylight saving time begins in the northern hemisphere between March–April and ends between September–November. [2]
Under the Standard Time Act of 1918, as amended by the Uniform Time Act of 1966, moving a state or an area within a state from one time zone to another requires a regulation issued by the Department of Transportation (DOT). [1]
The UK and Ireland which use GMT over winter switch to British Summer Time (BST) or Irish Summer Time (IST) respectively. [4]
Standard time begins in the northern hemisphere between September–November and ends between March–April. [2]
“An Act to preserve daylight and provide standard time for the United States” was enacted on March 19, 1918 (40 Stat 450). [1]
The daylight saving date in many countries may change from time to time due to special events or conditions.The United States, Canada and some other countries extended DST in 2007. [...] Many countries in the northern hemisphere may observe DST. [...] Today it is almost always one hour ahead, but throughout history there have been several variants on this, such as half adjustment (30 minutes) or double adjustment (two hours), and adjustments of 20 and 40 minutes have also been used. [2]
Sources:
[1] Daylight saving time in the United States - Wikipedia, the …
[2] What is Daylight Saving Time?
[3] Daylight Saving Time Around the World 2011
[4] DST: Daylight Saving Time > When is DST?