At 2 a.m. on Sunday, Nov. 4, most U.S. residents will be moving their clocks back an hour to mark the end of Daylight Saving Time.
Yes, that's right: Clock confusion is upon us yet again.
Not all states, however, will observe the time change. Residents of Arizona, Hawaii and U.S. territories like Puerto Rico, Guam and the Virgin Islands will remain on their normal schedules.
According to TimeandDate.com, about 75 countries and territories have at least one location that observed Daylight Saving Time this year and will be implementing the changeover this fall. However, the website notes that "countries, territories and states sometimes make adjustments that are announced just days or weeks ahead of the change."
In the U.S., the upcoming time shift is part of a longstanding tradition in which most residents set their clocks ahead an hour in the spring ("spring forward") and turn them back an hour as winter approaches ("fall back").
This means that come Sunday morning on Nov. 4, many U.S. residents will have had an extra hour of shut-eye.
Why do we have Daylight Saving Time?
The idea behind Daylight Saving Time, wrote MSNBC in 2011, is to use the "extended daylight hours during the warmest part of the year to best advantage."
The time shift is said to reduce the need for lighting during the evening, which is why the changeover is considered an energy-saver.
However, experts are divided as to whether or not this true.
According to National Geographic, several studies conducted in recent years have suggested that Daylight Saving Time "doesn't actually save energy and may even result in a net loss."
The magazine wrote in March:
Environmental economist Hendrik Wolff of the University of Washington, co-authored a paper that studied Australian power-use data when parts of the country extended daylight saving time for the 2000 Sydney Olympics and others did not. The researchers found that the practice reduced lighting and electricity consumption in the evening but increased energy use in the now dark mornings -- wiping out the evening gains.
Other studies, however, have shown energy gains.
In an October 2008 report to Congress, for example, the U.S. Department of Energy asserted that the changeover in the spring does save energy.
According to the Scientific American, senior analyst Jeff Dowd and his colleagues at the U.S. Department of Energy investigated what effect extending Daylight Saving Time would have on national energy consumption by looking at 67 electric utilities across the country.
"They [concluded that a] four-week extension of daylight time saved about 0.5 percent of the nation’s electricity per day, or 1.3 trillion watt-hours in total. That amount could power 100,000 households for a year," the science magazine wrote in 2009.
Brief history:
Benjamin Franklin has been credited with the idea of Daylight Saving Time, but Britain and Germany began using the concept in World War I to conserve energy, the Washington Post observes. The U.S. used Daylight Saving Time for a brief time during the war, but it didn't become widely accepted in the States until after World War II.
In 1966, the Uniform Time Act outlined that clocks should be set forward on the last Sunday in April and set back the last Sunday in October.
That law was amended in 1986 to start Daylight Saving Time on the first Sunday in April, but the new system wasn't implemented until 1987. The end date was not changed, however, and remained the last Sunday in October until 2006.
Nowadays, Daylight Saving Time begins on the second Sunday in March and ends on the first Sunday in November.
In 2013, Mar. 10 marks the beginning of Daylight Saving Time. Until then, enjoy standard time to the fullest.
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