DAYLIGHT SAVINGS:

Clock says it’s time to fall back

Friday, Oct. 31, 2008 | 10:06 a.m.

Daylight Saving Time officially ends for this year at 2 a.m. Sunday for the United States. Las Vegas Valley residents will join the rest of the country by enjoying an extra hour of sleep come Sunday morning.

Changing time to suit people's activities goes back to an idea Benjamin Franklin, signer of the U.S. Declaration of Independence and inventor, had while he was in Paris in 1784.

But the idea didn't go anywhere until London builder William Willett gave it serious consideration in 1907 in Great Britain.

The railroads in the United States and Canada first pushed standard time in the 1800s, but Daylight Saving Time formally appeared in the United States in 1918 in World War I, largely as an energy conservation measure.

During World War II, President Franklin Delano Roosevelt instituted year-round Daylight Saving Time, called "War Time," from Feb. 9, 1942, until Sept. 30, 1945.

From 1945 through 1966 the states were not required to leap forward and some, such as Arizona, remained on standard time year round.

On Jan. 4, 1974, President Richard Nixon signed the Emergency Daylight Saving Time Energy Conservation Act of 1973. The U.S. Department of Transportation followed that law by doing a study in 1975 that showed jumping ahead one hour during the summer months of June, July, August and September saved about 1 percent of household energy used by lighting, appliances and televisions because most people spent the extra daylight hours outside.

A recent study by Swedish researchers, however, analyzed 20 years of data and the scientists discovered that people's hearts loved falling back an hour instead of springing forward. The number of heart attacks drop the Monday after people return to standard time and increase in the week following the leap forward in springtime. An extra hour of sleep may contribute to heart health, the study said when it appeared in the New England Journal of Medicine on Thursday.

So while all states will fall back on Sunday, residents in Arizona and Hawaii won't have to meddle with their clocks: they remain on standard time and don't switch that dial.