Ready or not, daylight saving time is fast approaching.

On Sunday, Nov. 5 at 2 a.m. local time, our clocks will go back an hour and we will gain an extra hour of sleep, part of the twice-annual time change that affects most, but not all, Americans.

In March, daylight saving time will begin again for 2024, when we set our clocks forward and lose an extra hour of sleep.

We gain an hour in November (as opposed to losing an hour in the spring) to accommodate for more daylight in the mornings. When we "spring forward" in March, it's to add more daylight in the summer evenings. In the Northern Hemisphere, the autumnal equinox was Sept. 23, marking the start of the fall season. 

Here's what you should know about daylight saving time.

When does daylight saving time begin in 2024?

In 2024, daylight saving time will begin at 2 a.m. on Sunday, March 10 and end for the year at 2 a.m. on Sunday, Nov. 3.

PSA:With daylight saving time beginning, change your smoke alarm batteries

Why do we have daylight saving time?

In 1966, Congress passed the Uniform Time Act, standardizing the length of daylight saving time, which runs from March to November. 

Daylight saving time begins on the second Sunday of March each year and ends on the first Sunday of November.

The Department of Transportation said daylight saving time saves energy, prevents traffic injuries and reduces crime. The DOT oversees time zones and the uniform observance of daylight saving time because the railroad industry first instituted time standards.

Study:Making daylight saving permanent could save more than 30,000 deer every year

Do all states observe daylight saving time?

No, not all states and U.S. territories participate in daylight saving time.

Hawaii and Arizona (with the exception of the Navajo Nation) do not observe daylight saving time, and neither do the territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico and the U.S. Virgin Islands.

More:This state doesn't adjust its clocks to observe daylight saving time. Here's why.

Are we getting rid of daylight saving time?

In 2022, the U.S. Senate unanimously approved the "Sunshine Protection Act," a bill that would make daylight saving time permanent starting in 2023. That measure was not passed in the U.S. House of Representatives and was not signed into law by President Joe Biden.