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When is 2023 Daylight Savings Time? Overview and History

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Let's dive into the exciting world of daylight saving time! On Sunday, March 12, 2023, at 2 a.m. local time, the clocks will make a leap forward by one hour, ushering in the start of daylight saving time. This annual springtime tradition will come to an end on Sunday, Nov. 5, 2023, at 2 a.m. local time, when the clocks will fall back an hour. Believe it or not, this time change has roots dating back to World War I.

In 2022, the U.S. Senate gave an overwhelming thumbs up to make daylight saving time a permanent fixture, although the proposal hit a roadblock in the U.S. House. Fast forward to March 2, 2023, when U.S. Sen. Marco Rubio (R-FL) reintroduced the Sunshine Protection Act of 2023 to the 118th Congress. Fingers crossed!

You won't want to miss an important meeting or event, so it's essential to know when the time change occurs. Our handy guide will give you the scoop on when daylight saving time starts and ends during the year. Plus, we'll explore why we have daylight saving time in the first place and some interesting myths and facts surrounding this annual time warp. Let's get started!

When Does the Time Change Happen?

Have you been wondering when the time change will occur? Well, historically, the start and end dates for daylight saving time (DST) have fluctuated over time due to various U.S. government statutes, according to the U.S. Naval Observatory (USNO).

Since 2007, the start of DST in the U.S. is slated for the second Sunday of March, and at 2 a.m. local standard time, individuals will set their clocks forward by one hour, leading to a local time of 3 a.m. daylight time. DST will then come to a close on the first Sunday in November, when the clocks are set back by one hour at 2 a.m. local daylight time, marking a return to 1 a.m. standard time.

The History of Daylight Savings Time

Have you ever wondered why we have daylight saving time (DST)? Well, it turns out that the idea of resetting clocks in the summer months to conserve energy dates back to none other than Benjamin Franklin, who wrote a clever letter to the Journal of Paris in 1784 highlighting the benefits of taking advantage of extra evening daylight. However, it took over a century for the concept to become a reality, with Germany introducing DST in 1916 as a way to conserve fuel during World War I, followed by the rest of Europe, and the United States adopting DST in 1918.

Despite President Woodrow Wilson's desire to keep DST after World War I, the largely rural population of the U.S. objected, as farmers, in particular, would lose an hour of morning light. Thus, DST was abolished until the start of World War II, when President Franklin Roosevelt brought it back into effect year-round, dubbing it "War Time" in February 1942.

After the war ended, chaos ensued as different U.S. states and towns had their own rules for observing DST. To combat this, Congress enacted the Uniform Time Act in 1966, which mandated a uniform protocol throughout each state that followed DST. This meant that DST would begin on the first Sunday of April and end on the last Sunday of October.

Finally, in 2007, the Energy Policy Act of 2005 extended the length of DST to the present timing, with the start of DST now taking place on the second Sunday of March and the end on the first Sunday of November.

What is the Point of DST?

Have you ever wondered why we have daylight saving time (DST)? Well, it turns out that DST was first introduced in the U.S. during World War I and reinstated during World War II as part of the war effort. The nominal reason behind DST has been to save energy. However, research shows that the evidence for any significant energy savings is slim, as the benefits of DST have shifted over time.

Today, those who observe DST take advantage of the natural daylight in the summer evenings. As Earth moves from winter to spring and summer, the days start getting longer, with the longest day of the year on the summer solstice. During the summer season in each hemisphere, Earth, which revolves around its axis at an angle, is tilted directly toward the sun. Regions farthest from the equator and closer to the poles get the most benefit from the DST clock change, as they experience more dramatic changes in sunlight throughout the seasons.

More daylight in the evenings may result in fewer traffic accidents and encourage outdoor exercise for full-time workers. While brighter evenings may save on electric lighting, heating and cooling likely matter more, particularly for longer, hotter evenings of summer DST.

Studies have found that the four weeks of extra DST in the U.S. in 2007 saved only about half a percent of energy that would have otherwise been used on each of those days, and a 1998 study in Indiana found a small increase in residential energy usage after implementation of DST in some counties. Temporary changes in Australia's DST timing for the 2000 summer Olympics also failed to save any energy.

Ultimately, energy conservation is likely not the primary reason the U.S. continues to observe DST. According to Stanton Hadley, a retired senior researcher at Oak Ridge National Laboratory, the desire to take advantage of evening light is the primary driver behind DST.

Where is Daylight Savings Time Observed?

Daylight Saving Time (DST) is observed in many countries worldwide, with varying start and end dates. In the United States and Canada, most areas observe DST, with Hawaii and Arizona being the exceptions. In Canada, nine of the ten provinces observe DST, with some areas in British Columbia, Saskatchewan, northwest Ontario, and east Quebec following standard time all year. In Europe, most countries observe DST, with Russia, Iceland, and Belarus being exceptions. DST is called British Summer Time (BST) in the United Kingdom and Central European Summer Time (CEST) in Austria, France, Germany, Italy, Hungary, Norway, Poland, Spain, and Switzerland, among others. In the Southern Hemisphere, countries like Australia, New Zealand, South America, and southern Africa observe DST from September through November and move back to standard time during March and April.

There have been attempts to make DST permanent or to abolish it altogether in some areas. In the United States, for example, at least 19 states had introduced legislation to make standard time permanent as of 2022, while some areas in Australia, such as Queensland and the Northern Territory, do not observe DST at all. In Europe, recent polls showed that the majority of citizens surveyed wanted to end the practice of changing clocks twice a year, and if the lawmakers and member states agree, the EU members could decide to keep the EU in summer time or winter time.

While the main purpose of DST has been to save energy, evidence for its significant energy savings is slim. Instead, DST offers more daylight in the evenings, which can lead to fewer traffic accidents and more outdoor exercise. Ultimately, the decision to observe DST or not is up to individual countries and regions.

Daylight Savings Time Research

There has been a significant amount of research conducted on the effects of daylight saving time (DST) on various aspects of life, including energy consumption, traffic accidents, workplace injuries, and even heart attacks.

One study published in the journal Open Heart in 2014 found that heart attacks increased by 24% on the Monday following the "spring forward" switch to DST compared to the daily average for the weeks surrounding the start of DST.

Another study published in the Journal of Applied Psychology in 2009 showed that mine workers got 40 minutes less sleep and had 5.7% more workplace injuries during the week following the "spring forward" into DST compared to any other days of the year.

Research has also suggested that with more daylight in the evenings, there are fewer traffic accidents as there are fewer cars on the road when it's dark outside. More daylight also could mean more outdoor exercise for full-time workers.

The nominal reason for DST has long been to save energy, but the evidence for any significant energy savings is slim. However, a report published on Sept. 30, 2020, found that the four weeks of extra daylight saving time that went into effect in the United States in 2007 did save some energy, about half of a percent of what would have otherwise been used on each of those days.

Overall, the research on DST is mixed, and there are both positive and negative effects of the time change on various aspects of life.

Myths About DST

There are several myths surrounding daylight saving time. For example, there is a popular belief that DST was instituted to help farmers, but in reality, farmers were opposed to it as they lost an hour of morning light. Additionally, there is a myth that the time change saves energy, but the evidence for significant energy savings is slim.

On the other hand, studies have shown that the "spring forward" switch to DST can lead to more heart attacks, workplace injuries, and disruptions for pets. Before the Uniform Time Act was passed in the United States, different regions could or could not observe DST, leading to chaos and multiple time changes along a single bus route.

The fact that the time changes at 2 a.m. in the U.S. may have to do with practicality, as it's late enough that most people are home but early enough not to affect early shift workers and churchgoers.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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