Daylight Saving Time in the United States starts on the second Sunday of March and ends on the first Sunday of November

The mnemonic used to remember how Daylight Saving Time works is "Spring forward, Fall back". This means that in the Spring the clocks go forward one hour - from 2 a.m. to 3 a.m. - and in the Fall, they are set back one hour again - at 2 a.m. they go back to 1 a.m. 

In 2021, Daylight Saving Time starts on March 14, and ends on November 7. 

In the United States, most regions observe Daylight Saving Time, apart from the states of Arizona and Hawaii, and the territories of Puerto Rico, Guam, American Samoa and the U.S. Virgin Islands. 

Even though the different U.S. states observe distinct time zones in their region, Daylight Saving Time happens at 2 a.m. for everyone, regardless of what time zone they're in. This means that in some states, Daylight Saving Time starts earlier than in others. 

Spring Forward, Fall Back

Daylight Saving Time Starts

These are the dates for the beginning of Daylight Saving Time, when the clocks go forward, in the United States in the next few years:

Year DST Starts
2021 March 14, at 2 a.m.
2022 March 13, at 2 a.m.
2023 March 12, at 2 a.m.
2024 March 10, at 2 a.m.
2025 March 9, at 2 a.m.

Learn more about when Daylight Saving Time starts.

Daylight Saving Time Ends

On the last Sunday in November, the clocks move back again one hour, ending the Daylight Saving Time and going back to Standard Time. Here are the dates for the end of DST in the following years:

Year DST Ends
2021 November 7, at 2 a.m.
2022 November 6, at 2 a.m.
2023 November 5, at 2 a.m
2024 November 3, at 2 a.m.
2025 November 2, at 2 a.m.

Here is more information about when Daylight Saving Time ends

Why do we have Daylight Saving Time?

Throughout history, Daylight Saving Time has been used on and off in the United States. It was first implemented in 1918, during World War I, in an effort to save fuel and electric power. However, soon after the war, Daylight Saving Time was abolished. 

Daylight Saving Time was adopted again from 1942 to 1945, during World War II, although back then it was known as "War Time" and was observed all year long. This had the same purpose as it did during the First World War, to save power and electricity for the war effort. 

Daylight Saving Time as we know it today, starting in March and ending in October, was established by President Nixon in 1974. The purpose of Daylight Saving Time is to make the most use out of the longer periods of daylight that we have in the Summer, by taking away one hour from the morning and giving people an extra hour in the evenings. 

The Effects of Daylight Saving Time

Woman napping

Some studies suggest that the change in hours that occurs with Daylight Saving Time, has several negative effects on people's health and brains. On the day after the Daylight Saving Time change takes place, hospitals tend to receive more heart attack patients than usual and there seem to be more vehicle accidents on the roads. 

This is because the change from standard time to Daylight Saving Time severely impacts our quality of sleep. Even though we only lose one hour of sleep during this transition, that is enough to impact the circadian rhythm that regulates our sleep. After the change, our brains also have trouble adjusting to the new cycles of light and darkness. 

Sleep is essential to maintain good health, so if we're not getting enough of it impacts our whole life. Some people may be so affected by this change that they suffer from insomnia, and many others who struggle to adapt to the new times can feel tired and irritable. 

Luckily, Dr. William Anthony from Boston University realized this in 1999 and founded National Napping Day. This day takes place on the Monday after Daylight Saving Time starts, and gives people the opportunity to nap and make up for the lost hour of sleep.