Explained: How Daylight Saving Time Works, Which Countries Change The Clock And What Lebanon Has Done ThIs Year

Daylight saving time, or the practice of shifting the clock an hour ahead, aims to maximise sunlight in the summer months. This year, Lebanon has decided to delay the practice by a month.

Several countries in the Northern Hemisphere set their clocks ahead one hour in late March or in April, and then set back the clocks one hour in late September or October. This practice is called daylight saving time.

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Due to a dispute between political and religious authorities In Lebanon over a decision to start daylight saving time next month, the country woke up in two time zones on March 26, 2023. Daylight saving time, or summer time, is a system for uniformly advancing clocks, which extends the daylight hours during conventional waking time in the summer months. Waking time refers to the hours in a day a person is awake. 

On March 23, Lebanon's caretaker prime minister Najib Mikati announced that the daylight saving time will not start over the last weekend of March, the conventional practice in Lebanon, Europe and other regions, but will instead commence on April 20, news agency Reuters reported. When daylight saving time will begin, the clocks will be set ahead one hour. 

According to a Reuters report, it is speculated that the delay in starting the daylight saving time is to allow Muslims observing the holy month of Ramadan to break their daylight-hours fasts at the correct time, rather than an hour earlier, which would have been the case had the clocks been set an hour ahead. 

However, the Maronite Church, Lebanon's largest Christian church, has opposed this decision, stating that there had been no considerations of international standards.

Now, a question arises about how exactly daylight saving time is beneficial to some countries. Here's everything you need to know about daylight saving time.

How daylight saving time works

Daylight saving time, or the practice of shifting the clock an hour ahead, aims to maximise sunlight in the summer months. Several countries in the Northern Hemisphere set their clocks ahead one hour in late March or in April, and then set back the clocks one hour in late September or October. 

The practice of daylight saving time is followed in many countries because they believe that the time shift will allow them to use the hours before sunset more productively. However, some studies have shown that this practice can be detrimental to people's health. 

In the United States, this year's daylight saving time began on March 12, and will end on November 5. 

In the US, clocks were changed at 2:00 am local time on the second Sunday in March, and made to move one hour forward. This practice causes people to lose one hour of sleep. 

On the first Sunday in November, daylight saving time will end at 2:00 am. The clocks will be made to fall back by an hour, and observers will gain an hour of sleep. In other words, when daylight saving time ends, the clocks are set to the standard time.

Since Earth's axis is tilted with respect to its orbital plane, the world experiences seasons. Earth rotates on its axis at a relatively constant 23.4-degree angle relative to its orbit around the Sun, which means that the Equator usually has roughly 12 hours of both day and night the entire year, but the regions north and south of it do not.

When the Northern Hemisphere leans towards the Sun, it is summer for that hemisphere, and winter for the Southern Hemisphere. The Northern Hemisphere will witness longer and warmer days, while the Southern Hemisphere will experience shorter and colder days. The situation reverses six months later, when the Southern Hemisphere tilts towards the Sun. 

Daylight saving time was implemented at a time when lights were powered by coal, according to an article by The National Geographic. The practice added an hour in the summer months so that people got an extra hour of sunlight to end the workday. In the winter, an hour was removed, because the days are shorter, and it was important to align the clocks with the original time to make the most out of sunlight. 

The participation of a country in this practice depends on how far it is from the Equator. Countries that are farther away from the Equator have a more pronounced difference between daytime and nighttime hours, and hence, are more likely to follow the practice of daylight saving time.

Does daylight saving time benefit people?

While many people believe that daylight saving time helps them be more productive, many argue that the practice makes them miss meetings or results in poor sleep. 

According to some studies, springing the clocks forward was linked with an increase in heart attacks, while setting the clocks an hour back was associated with a decrease in heart attacks.

The shift in time is also linked to an increase in fatal car accidents, the National Geographic article said.

The immune system is also affected due to sleep loss which can occur as a result of daylight saving time. 

Some studies have suggested that daylight saving time has resulted in increased energy savings. According to a 2008 study from the US Department of Energy, an extra four weeks of daylight saving time in the US saved about 0.5 per cent in total electricity a day. This could be because people woke up an hour earlier than usual, resulting in them working an extra hour till sunset. 

However, some people believe that the situation is a wash, because despite the fact that the later sunlight hours often reduce electricity use during that time, the practice also causes people to use more air-conditioning in the evening, or more electricity to light up the dark mornings.

These impacts could be specific to certain locations. According to a 2011 study conducted by the Massachusetts Institute of Technology, daylight saving time caused an increase in energy demand and pollution emissions in Indiana. Meanwhile, in Norway and Sweden, there were slight reductions in energy use, according to a different study.

The time shift helps people indulge more in evening activities because several people tend to go for walks and take their children to parks when it is light after work. The petroleum, golf and barbecue industries have particularly benefited from the practice of daylight saving time. 

However, the time shift is not popular in Europe, as suggested by a survey that revealed about 80 per cent of around 4.6 million respondents were against daylight saving time. 

History of daylight saving time

American author Benjamin Franklin was the first to suggest the practice of daylight saving time. He wrote about this practice in an essay in 1784. It was a satirical letter written for the Journal de Paris. 

Franklin wrote that he was astonished to see the Sun rise at the early hour of six in the morning, long before most Parisians ever saw the light of the day. 

Franklin wrote that if people rose with the Sun, Paris would save an "immense sum" from the candles burned in the dark evening hours, the National Geographic article said. However, Franklin never suggested a shift in clocks, and instead offered solutions to people not waking up early in the morning that included firing cannons in the street, and taxes for shuttered windows.

In 1895, George Hudson, an entomologist from New Zealand, suggested a two-hour shift to allow for more bug hunting post work. 

British builder William Willett campaigned for setting the clock ahead by 80 minutes in four moves of 20 minutes each during April, and the reverse in September, according to Britannica. He proposed this idea to prevent wasting daylight.

The British House of Commons, in 1909, rejected a bill to advance the clock by one hour in the spring and return to Greenwich Mean Time, the mean solar time at the Royal Greenwich Observatory in England, in the autumn.

During World War I, several countries, including Australia, Great Britain, Germany and the US, adopted daylight saving time to conserve fuel by reducing the need for artificial light. 

The first seasonal time shift took place in the US in 1918.

Clocks were kept continuously advanced by an hour in some countries during World War II. From February 9, 1942 to September 30, 1945, clocks were kept advanced by an hour in the US.

During World War II, England used "double summer time". They advanced their clocks two hours from Standard Time during the summer. 

Countries that follow daylight saving time

About 40 per cent of the countries in the world follow daylight saving time.

Earlier, daylight saving time began in the US on the last Sunday in April and ended on the last Sunday in October. The US Congress passed a law in 1986 that since 1987, the daylight saving time will start on the first Sunday in April. The end date was not changed.

Daylight saving time in the US was changed again in 2007. The start date of daylight saving time was moved to the second Sunday in March and the end date was shifted to the first Sunday in November. 

As many as 19 states in the US have passed legislation or resolutions to adopt permanent daylight saving time. The Sunshine Protection Act, which was passed in the Senate in 2022, aimed to make daylight saving time permanent in the US, but was revoked in the House of Representatives. 

Hawaii, the territories of Guam, American Samoa, the Northern Mariana Islands, Puerto Rico, and the US Virgin Islands, and most of Arizona, excluding the Navajo Nation, have entirely opted out of daylight saving time. 

Most of North America, New Zealand, Europe, and a few regions of the Middle East practise daylight saving time, but have different start and stop dates. The majority of Africa and Asia do not practise daylight saving time. 

Afghanistan, Bahrain and Indonesia are some countries that have never used daylight saving time. 

India used daylight saving time from 1941 to 1945. 

Most countries of western Europe follow the practice of starting daylight saving time on the last Sunday in March, and ending the daylight saving time on the last Sunday in October.

However, Europe may opt out of daylight saving time. The European Union, in 2019, voted to end the mandatory time shift. However, negotiations on the matter are currently stalled.