(CNN) -- This could go either way.
You're reading this with a clear head and a satisfied feeling of having gotten a really good night's rest.
Or, you're shaking your head and wondering why in the world you forgot to set your clock back and take advantage of that extra hour of sleep.
That's right. Daylight saving time is over, and clocks adjusted back an hour at 2 a.m. Sunday
The change affects all those in the United States except for people in Hawaii and parts of Arizona who do not observe daylight saving time. The territories of Guam, Puerto Rico, U.S. Virgin Islands and American Samoa also do not recognize the change.
For those who do change the digits on their clocks, the sun will seem to come up earlier in the morning and set earlier at night, compared with Saturday.
The idea for daylight saving came from legendary American inventor, statesman and founding father Ben Franklin, who, in a 1784 letter to a French journal, suggested that Parisians could save thousands of francs annually by waking up earlier in the summer so they wouldn't have to buy so many candles to light the evening hours.
The United States didn't adopt the practice until the 20th century -- for a brief time during World War I, again during World War II, and on a state-by-state basis in the years after the war. It became a national policy, with some tinkering, beginning in 1966. Dozens of other countries now observe some form of daylight saving as well.
The extra hour that people will get this weekend will only last so long. Americans will have to give it back by "springing forward" -- and turning ahead their clock -- one hour on March 10, 2013.