It's that time of the year to turn the clock back an hour: Starting at 2 a.m. on Nov. 4, daylight saving time ends and clocks go back one hour.

What is the history of daylight saving time?

The idea was first floated in 1784 by one Benjamin Franklin. While serving as U.S. minister to France, he wrote the essay "An Economical Project for Diminishing the Cost of Light."

The idea failed to see the light of day until 100 years later, when the U.S. railroads instituted a standardized time for their train schedules.

That time change was imposed nationally during the first World War to conserve energy, but it was repealed after the war ended. It became the national time again during World War II.

After that, it was a free-for-all for states deciding if they wanted it, and when it would start and end. Congress finally enacted the Uniform Time Act in 1966, which decreed that if a state chose to opt in to daylight saving, it had to be at the same time as everyone else.

Why did daylight saving time change?

In 2005, the Energy Policy Act instituted a change to daylight saving time, extending it by four weeks.

As of 2007, daylight saving time runs from the second Sunday of March through the first Sunday of November. The reasoning behind the change: a savings of an estimated 10,000 barrels of oil a day through reduced use of power.

It is not at all certain that the change saves any energy at all. On the bright side, extended hours of daylight are certainly pleasant.

Who has opted out?

While most of the U.S. observes daylight saving time, Hawaii, Puerto Rico, the U.S. Virgin Islands and American Samoa don't. Most of Arizona opts out as well, except for the Navajo Nation.

Why does the time change happen at 2 a.m.?

It's the time that is considered to be least disruptive, both for business and to people worried about being an hour late to church services or brunch dates on Sunday.

According to the blog Life's Little Mysteries, moving the clock back an hour from 2 a.m. to 1 a.m. moves back only one hour in time, not back to the day before, which would only add to the confusion.