Daylight saving time: what is it and why do we have it?

Sign up for CNN’s Sleep, But Better newsletter series. ours The seven-part guide has helpful tips for better sleep.


It’s almost an hour to turn the clocks “back”.

On the first Sunday in November, at 2 a.m., clocks in most of the United States and many other countries go back one hour and remain in what is called standard time for nearly four months. On the second Sunday of March, at 02:00, the clocks go forward one hour to Summer Time.

Daylight Saving Time has its roots in train schedules, but was put into practice during World War I to save fuel and energy in Europe and the United States by extending daylight hours, according to the U.S. Department of Transportation’s Bureau of Transportation Statistics.

The US standardized the practice when it passed the Uniform Time Act of 1966. For eight months of the year, much of the US and dozens of other countries follow Daylight Savings Time. For the remaining four months, they follow standard time.

Pro tip: It’s Daylight Savings Time, with the special use of “savings” and not “savings.”

In the US, states are not allowed to “roll back” or “go forward” laws. Most of Hawaii and Arizona do not observe daylight saving time.

The biannual change is irritating enough for lawmakers of all political stripes that the US Senate approved in March to make Daylight Savings Time permanent. It was approved unanimously. The bill still needs to pass the House of Representatives and be signed by President Joe Biden to become law. If approved, the change would not take effect until November 2023.

Benjamin Franklin may have been the first to mention daylight saving time in 1784, when he wrote a letter to the editor of the Paris Journal. But it was not widely used until more than a century later.