It's time for clocks to "fall back" one hour, allowing many people across the United States to gain one hour of sleep.

On the first Sunday of November, at 2 a.m., clocks fall back an hour to standard time. On the second Sunday of March, at 2 a.m., clocks in most of the United States and many other countries move forward one hour and stay there for nearly eight months in what is called Daylight Saving Time.

The current March to November system that the U.S. follows began in 2007, but the concept of "saving daylight" is much older. Daylight Saving Time has its roots in train schedules, but it was put into practice in Europe and the United States to save fuel and power during World War I, according to the U.S. Department of Transportation's Bureau of Transportation Statistics .

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