Twice a year, Americans reset their clocks to reconcile shifting sunlight to time of day. The ritual starts again Sunday morning, with the clock change that hurts most, when time springs forward from 1:59 to 3 a.m., making for a 23-hour day and costing an hour of snoozing. That extra hour is on loan until Nov. 4, when standard time returns and clocks can fall back from 1:59 to 1 a.m.

WHAT'S THE PURPOSE? To save energy on artificial lighting. When night falls earlier, people must turn on lights sooner and burn them longer. Supposedly, it saves the equivalent of hundreds of thousands of barrels of oil per year. Another touted benefit has been reducing the likelihood of car wrecks.

WHO THOUGHT OF IT? Contrary to popular belief, it wasn't Benjamin Franklin. The English home builder William Willett first proposed changing clocks in a 1907 pamphlet, Waste of Daylight. On early-morning horseback rides, he was dismayed to see shutters closed on houses in what he felt was the most glorious sunshine of the day.

DAYLIGHT SAVING HISTORY

The 90-year history of daylight-saving time in the U.S. has roots in world wars and the capricious flow of Arab oil.

- 1918-1919: To save fuel during World War I, the United States passes a law establishing daylight saving from the last Sunday in March to the last Sunday in October. The law was repealed and daylight saving became a local option.

- 1942-1945: President Roosevelt sets up year-round "War Time." When it ends in 1945, adjusting clocks again becomes a local option, leading to confusion for airlines, railways and the broadcasting industry.

- 1967-1973: The Uniform Time Act of 1966 goes into effect, with daylight saving running from the last Sunday in April to the last Sunday in October. States could opt out, and five did.

- 1974: The Emergency Daylight Saving Time Energy Conservation Act of 1973, signed into law by President Nixon in response to an oil embargo, has daylight saving starting the first Sunday in January. Later that year, Congress amends the act and standard time returns the last Sunday in October.

- 1975: Daylight saving is from the last Sunday in February to the last Sunday in October.

- 1976-1986: Daylight saving runs from the last Sunday in April to the last Sunday in October.

- 1987-2006: The law is amended with the Federal Fire Prevention and Control Act of 1986, signed by President Reagan, extending daylight saving from the first Sunday in April to the last Sunday in October.

- 2007-PRESENT: The Energy Policy Act of 2005, along with providing tax incentives and loan guarantees for energy conservation efforts, lengthens daylight saving from the second Sunday in March to the first Sunday in November. Congress retains the right to revert to the 1986 law if energy savings aren't significant.

WHO DOESN'T USE DAYLIGHT-SAVING TIME? Afghanistan, China, Iran, Japan, Kazakhstan, Kuwait, Pakistan, Qatar, Saudi Arabia, Taiwan, Venezuela, Vietnam and North and South Korea don't touch their clocks.

In the U.S., opting out are American Samoa, the Commonwealth of Northern Mariana Islands, Guam, Hawaii, Puerto Rico, the Virgin Islands and Arizona (with the exception of the Navajo Nation's portion there).

-- Johnny Edwards

Sources: WebExhibits.org; PettsWood.org; wwp.GreenwichMeanTime.com; The New York Times; HuffingtonPost.com; AboveTopSecret.com; CarTalk.com; The Technique; EatTheState.org