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Why Do We Have Daylight Savings Time?

Here are the reasons for daylight savings time and how it impacts sleep.

When you think about daylight savings time, do you immediately think about getting more sleep or less? For some people, the time change is no big deal. But for a lot of people, daylight savings time means daytime sleepiness, sluggishness, and exhaustion.

Thankfully, though, all this can be avoided with a few easy changes to your routine in the week leading up to the time change. Before we get into how to adjust to daylight savings time, let’s take a brief look at its history, and why you may feel so tired after the change.

Daylight savings time, also known as daylight saving time (DST), was first used in Thunder Bay, Canada in 1908. It was intended to make as much use of daytime as possible and save energy. However, it was actually first invented in New Zealand in 1895.

The United States is only one of about 70 countries to use DST—however, parts of Arizona and all of Hawaii do not observe it. Daylight savings time in the U.S. begins at 2 a.m. local time on the second Sunday in March, when you “spring forward,” or set your clock forward one hour. It ends on the first Sunday of November when you set your clocks back an hour, or “fall back.”

The United States first observed DST in 1918, where it was called “Fast Time,” but it was repealed less than a year later. It was reintroduced by President Franklin D. Roosevelt during World War II, calling it “War Time.”

Until 1966, there were no set rules for daylight saving time, leading to a lot of confusion up until the passing of the Uniform Time Act of 1966. This gave areas that wanted to opt out of DST the opportunity to do so while also establishing a synchronized DST schedule across the whole country to keep things in sync after each time change.

The Difference Between Daylight Savings Time and Standard Time

The main difference between daylight savings time and standard time is that standard time is determined by science, while daylight savings time is determined by people.

Time in any location is influenced by the Earth’s position in relation to the sun, which is what creates the different time zones across the world. The earth rotates on its axis about 15 degrees per 60 minutes, and each 15-degree section becomes a time zone. Standard time is the local time of any region based on what time zone it exists in.

For example, the standard time in Los Angeles is different than the standard time in Miami, or the standard time in Sydney because they’re all located in different time zones. So while the sun is rising in Los Angeles, people in Sydney may be getting ready for bed.

Daylight savings time affects a location’s standard time by modifying it by one hour at the designated time each year—either an hour forward in spring or an hour backward in fall. When daylight savings time begins, it “adds” an hour to a location’s standard time. When it ends, you “lose” that hour as you return to your normal standard time.

Remember what I talked about above—daylight savings time was a concept created by people to make the most out of their time. So while it affects how we set our clocks, it doesn’t actually alter time itself.

Why Do You Feel Tired After Daylight Savings Time?

Daylight savings time may be intended to save energy, but it can have the opposite effect on your own body. This is because your circadian rhythm may fall out of alignment after the clock change.

Your circadian rhythm helps regulate your sleep cycle, and because it’s influenced by light exposure, the combination of the time change and changed light outside can cause circadian misalignment.

Who Is Affected Most By the Time Change?

Not everyone is affected by daylight savings time the same way. Some people may only feel groggy for a while. For others though, that sleep loss may put them at increased risk of heart attack or stroke, workplace injuries, or even fatal traffic accidents.

But people of a certain chronotype may actually be more affected by the time change.

A study from 2008 found that people who are most productive during the evenings—also known as night owls—have significantly more restless sleep following the time change.

Do you know if you are a night owl or a morning lark? Ask yourself the following questions:

  • Do you feel most alert in the early morning, or later in the evening?
  • Do you feel the sleepiest in the early evening or past midnight?
  • Do you enjoy waking up at 6 a.m. or earlier, or at 8 a.m. or later?
  • Do you have the most energy a few hours after waking up or a few hours before bed?

If you feel and function better during the morning hours, you are a morning lark. If you’re more productive and energized in the evening, you’re a night owl. This is a good start to help you find your ideal sleep schedule.

Sweet Dreams,

Michael J. Breus, Ph.D., FAASM

The Sleep Doctor

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