Mark your calendar, set your clocks on Nov. 6

Relax. Take your time. You've got an extra hour to burn when Daylight Saving Time reverts back to ordinary, standard time Sunday, Nov. 6. Before hitting the pillow on Saturday night, Nov. 5, take a few minutes to set all of your time machines back an hour. Then catch up on the hour of sleep you surrendered back in March. (Purists can wait until 2 a.m. Sunday if they have the patience.)

For the curious, see an abridged version of a National Graphic news story below, or click here for more details on the semi-annual clock change.

Brian Handwerk
National Geographic News

With daylight saving time (also called daylight savings) about to begin again, clock confusion is once again ticking away: When exactly does daylight saving time end? Why do we spring forward? Does it really save energy? Is it bad for your health? Get expert answers below.

The federal government doesn't require U.S. states or territories to observe daylight saving time, which is why residents of Arizona, Hawaii, Puerto Rico, the Virgin Islands, American Samoa, Guam, and the Northern Marianas Islands won't need to change their clocks this weekend.

Where it is observed, daylight savings has been known to cause some problems.

National surveys by Rasmussen Reports, for example, show that 83 percent of respondents knew when to move their clocks ahead in spring 2010. Twenty-seven percent, though, admitted they'd been an hour early or late at least once in their lives because they hadn't changed their clocks correctly.

It's enough to make you wonder—why do we do use daylight saving time in the first place?

How and When Did Daylight Saving Time Start?
Ben Franklin – of "early to bed and early to rise" fame – was apparently the first person to suggest the concept of daylight savings, according to computer scientist David Prerau, author of the book Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time.

While serving as U.S. ambassador to France in Paris, Franklin wrote of being awakened at 6 a.m. and realizing, to his surprise, that the sun would rise far earlier than he usually did. Imagine the resources that might be saved if he and others rose before noon and burned less midnight oil, Franklin, tongue half in cheek, wrote to a newspaper.

"Franklin seriously realized it would be beneficial to make better use of daylight but he didn't really know how to implement it," Prerau said.

It wasn't until World War I that daylight savings were realized on a grand scale. Germany was the first state to adopt the time changes, to reduce artificial lighting and thereby save coal for the war effort. Friends and foes soon followed suit.

In the U.S. a federal law standardized the yearly start and end of daylight saving time in 1918—for the states that chose to observe it.

During World War II the U.S. made daylight saving time mandatory for the whole country, as a way to save wartime resources. Between February 9, 1942, and September 30, 1945, the government took it a step further. During this period daylight saving time was observed year-round, essentially making it the new standard time, if only for a few years.

Since the end of World War II, though, daylight saving time has always been optional for U.S. states. But its beginning and end have shifted—and occasionally disappeared.

During the 1973-74 Arab oil embargo, the U.S. once again extended daylight saving time through the winter, resulting in a one percent decrease in the country's electrical load, according to federal studies cited by Prerau.

Thirty years later the Energy Policy Act of 2005 was enacted, mandating a controversial monthlong extension of daylight saving time, starting in 2007.

But does daylight saving time really save any energy?
(Continue)

Published 10-28-2011