Why Do We Have Daylight Saving Time?


In many countries across the world, people adjust their clocks forward by one hour in the spring to mark the beginning of daylight saving time. This special period of timekeeping then ends in the fall. Learn more about this practice, including where it originated, why countries continue to engage in it, and what alternatives are being proposed.

What Is Daylight Saving Time?

Daylight saving time (DST) is the period between spring and fall when many people change their clocks forward one hour. Currently, in the United States, people "spring forward" by setting clocks ahead an hour the second Sunday in March and "fall back" by setting clocks back an hour the first Sunday in November. In Europe, where daylight saving time is often referred to as "summer time," the biannual changing of the clocks begins in late March or early April, then ends in September or October.

Around the world, approximately 76 countries, which account for over 1.6 billion people, participate in daylight saving time. However, many countries located near the equator do not change their clocks seasonally since daylight hours remain somewhat constant throughout the year in that area.

When Did Daylight Saving Time Start?

People debate who created daylight saving time and when the practice began. Some claim Benjamin Franklin first proposed the idea of adjusting clocks in the summer to provide extended daylight. In his 1784 letter to the editor of the Journal of Paris, Franklin suggested that beginning and ending the day based on sunrise and sunset would reduce candle waste and save energy.

A handful of others outlined similar ideas throughout the following decades, but the Canadian city of Port Arthur is said to be the first city in the world to implement daylight saving time, in  1908. Germany was the first country to officially establish daylight saving time in 1916 during World War I, in order to conserve fuel. Most of Europe and then the U.S. followed soon after.

After World War I ended, U.S. farmers objected to the continuation of daylight saving time because they did not want to lose an hour of morning light. The U.S. reinstated daylight saving time with clocks kept continually advanced for over two years, during World War II. Daylight saving time was not consistently practiced across the entire country during non-war time until the Uniform Time Act, enacted by Congress in 1966.

Why Do We Have Daylight Saving Time?

Daylight saving time was originally started to conserve energy. The general thought was that an extra hour of daylight in the evening would reduce the use of electricity in homes. However, there is little evidence of the time change resulting in lower energy consumption.

In 1975, the U.S. Department of Transportation conducted a study and found that daylight saving time saved approximately 1% of energy, but a follow-up review concluded that the results were statistically insignificant. A 2008 study found that daylight saving time actually increases residential electricity use and pollution.

Lighting was a major factor in the initial discussions of energy conservation and daylight saving time. However, lighting has become increasingly energy efficient over time. Other factors, such as heating and cooling, may more greatly influence energy usage currently.

Should Daylight Saving Time Be Permanent?

Most U.S. states participate in daylight saving time. Arizona and Hawaii are currently the only U.S. states in which people do not change their clocks in spring and fall. However, between 2015 and 2019, 29 U.S. states introduced legislation in favor of year-round daylight saving time, hoping to eliminate the process of changing clocks twice per year.

A 2020 survey from the American Academy of Sleep Medicine found that 63% of Americans support the elimination of seasonal time changes and would prefer a national, fixed, year-round time. Sudden time change may cause a ripple of negative effects, such as an increase in workplace injuries, largely due to lost sleep. However, there is still much debate over exactly which fixed time should be used nationally — permanent daylight saving time or permanent standard time, which is the time used in the non-daylight saving time months.

Arguments for Permanent Daylight Saving Time

Several senators recently reintroduced the Sunshine Protection Act, originally proposed by Florida in 2018, which calls for permanent daylight saving time. Those in favor of permanent daylight saving time argue that it can:

Reduce Risk of Stroke and Heart Attack: Research shows that there is an increase in both strokes and heart attacks after the two yearly daylight saving time transitions. More research is needed, however, to determine if eliminating daylight saving time would truly reduce the total number of strokes and heart attacks over the long-term.

Reduce Seasonal Depression: One study found that there was an increase in depressive episodes following the transition from daylight saving time back to standard time. The authors determined that the increase was likely due to the sudden loss of an hour at sunset, which becomes a triggering biological reminder that shorter, colder winter days are coming.

Promote Physical Activity: Extending daylight saving hours may promote outdoor activities. One study found that 62% more people are found walking and 38% more people are found riding a bicycle during daylight saving time.

Benefit the Economy: A study by JPMorgan Chase Institute found that the start of daylight saving time in spring prompts an increase of daily card spending per capita by 0.9% in the Los Angeles area, while the end of daylight saving time sees a reduction in daily card spending per capita by 3.5%.

Reduce Car Crashes and Crime: The U.S. Department of Transportation claims the extended daylight hours of daylight saving time save lives because fewer drivers after dark translates to a reduction in car crashes. They also claim daylight saving time reduces crime because fewer people are out after dark. People use these claims to deduce that extending daylight saving time year-round would lead to reduced car crashes and crime year-round.

Arguments for Permanent Standard Time

Rather than permanently using daylight saving time, some argue that staying in standard time year-round makes more sense from a biological point of view. Those in favor of permanent standard time have argued that doing so would have the following benefits.

Promote Proper Circadian Alignment: Our bodies are influenced by light in many ways, especially in regards to when we feel tired and awake. The Society for Research on Biological Rhythms and American Academy of Sleep Medicine claim that standard time is more consistent with the body’s natural biological clocks or circadian rhythm. These experts believe that when the circadian rhythm becomes misaligned, it can create a ripple effect of other health risks, such as cardiovascular disease and metabolic syndrome.

Reduce Car Crashes: Although some argue that permanent daylight saving time could reduce car crashes, others argue that permanent standard time could have the same effect. One study found that fatal car crashes increased by 6% after the transition into daylight saving time in the spring. Mornings were particularly risky, and researchers hypothesize that an extra hour of daylight in the mornings could significantly reduce fatal car accidents.

Promote Productivity and Benefit the Economy: People often lose sleep the first night or two as they transition into daylight saving time. Because sleep is tied to productivity, some argue that this sleep loss could negatively affect the economy. Also, one study found that adding just one extra hour of sleep per night on a long term basis can increase wages by 16%. If year-long standard time increases sleep, it could benefit both productivity and the economy.

Keep Children Safer: People believe year-long standard time could keep children safer by reducing the time they have to spend waiting for school buses or walking to school in morning darkness during daylight saving time. A 2017 report by the National Highway Traffic Safety Administration stated that 75% of pedestrian fatalities occur in the dark. However, it is not clear whether morning darkness poses a greater risk than evening darkness.

As the arguments for permanent daylight saving time and permanent standard time continue in the U.S., the European Union (E.U.) has made the first steps toward eliminating the seasonal time change. Under their draft directive, the E.U. would allow each individual country to decide whether to use permanent standard time or permanent daylight saving time. It is possible that the U.S. will eventually follow the lead of the E.U.


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