Do not forget to set your clocks ahead this weekend.
Why are we doing this?
In the US, DST was used during the first and second world wars to (ostensibly) conserve energy; during WWII it was referred to as “war time.” DST has value in temperate zones where the daylight to darkness ratio changes considerably from summer to winter. This allows for the human sleep/awake cycle to generally align better with darkness/daylight. The intended effect is less energy consumption. There are some critical arguments against this, however.
Prior to 1966, states and localities were allowed their own discretion whether to use DST locally. After that, the US established the Uniform Time Act that mandated the use of DST; states that wanted to be exempt could do so by passing a state law. During President Nixon’s administration the energy crisis prompted the government to extend DST; this, however turned out to be a bad thing; people and kids were going to work and school in the dark during wintertime. The mandate was overturned thereafter.
In 2007, DST will begin on the second Sunday in March and extend to the first Sunday of November, but if no energy savings can be shown from the extension after the U.S. Department of Energy completes a study of impact of the change, Congress may revert back to the schedule set in 1986 after that.
Why do some states and territories not observe DST?
Arizona (except for the Navajo Nation), Hawaii, Puerto Rico, Virgin Islands, Guam, and American Samoa do not observe DST and stay on “standard time” all year. If you’ve ever spent any time in the summer sun in those regions you probably understand why another hour of sunlight might be undesirable.
And don’t get me started on DST management in Indiana.