For two decades, Daylight Saving Time has begun on the first Sunday in April and ended on the last Sunday in October. It wasn't always so. Though subject to a higher power in most realms, time must also obey Congress.

And so, at 2 a.m. Sunday, it will spring forward one hour. Come fall, at 2 a.m. on Oct. 29 to be exact, people who want to be in sync with their neighbors will move their clocks back an hour.

But next year, things will change again. To save energy, Congress decreed that in 2007, clocks will be moved ahead earlier and back later to add three weeks of Daylight Saving Time.

This is hardly the first time Congress has messed with time itself. In the 1970s, the U.S. Department of Transportation calculated that the nation uses 1 percent less energy when Daylight Saving Time is in effect.

In 1974, during the Arab oil embargo and the energy crisis, Daylight Saving Time began on Jan. 6. The next year, it began on Feb. 23. Congress has changed the timing of the switch-over at least twice since then.

To add to the confusion, not every state uses Daylight Saving Time. Hawaii doesn't believe in it. Nor does Arizona, although some American Indian reservations there observe it.

Time is even more out of joint in other nations. Some embrace the energy-savings policy and some don't. Since there's no advantage to jerking time back and forth in countries near the equator, they don't do it.

Australia, one of the first countries to adopt Daylight Saving Time, is in a world of its own. There, time zones in summer change as one moves both horizontally and vertically across the continent. Some zones add a half-hour of daylight, others an hour.

Blame night owl Benjamin Franklin for this madness. The diplomat, patriot, publisher, scientist, bon vivant and wit proposed Daylight Saving Time in Paris in 1784. In a short discourse entitled An Economical Project, he feigned astonishment at the early hour of the rising of the sun.

Franklin wrote that he was awakened in his Paris lodgings by a noise, noticed that his room was awash with light and consulted his watch. To his shock it said 6 a.m. He checked an almanac and, sure enough, the sun really does rise that early.

"Your readers," he wrote in a letter to a Parisian newspaper editor, "will be as much astonished as I was, when they hear of his rising so early; and especially when I assure them, that he gives light as soon as he rises. I am convinced of this."

Like teenagers and college students today, Parisians stayed up well into the night and slept until noon. They burned a lot of extra lamp oil and candle wax as a result. Between March and September, when days were long, if they got up with the sun and went to bed at sunset, Franklin computed Parisians would save 64 million pounds of tallow and wax and a fortune spent on candles. To encourage them to do so, he proposed that the government tax window shutters and fire cannons every morning at 4 a.m. "to awaken the sluggards."

The United States hasn't gone that far yet, but with gas prices high and utility companies threatening brownouts and blackouts by 2008, Franklin's ideas may yet find some friends in Congress.