Daylight Saving Time. Why do we change the clocks?
The tradition of moving clocks forward during the summer months is known around the globe as Daylight Saving Time (DST). With the arrival of spring, people set the clocks one hour forward from the standard time. Although this practice is peculiar to the majority of the western countries, not all regions and states accept DST.
How does DST work?
Around the globe, people set clocks one hour forward on the last Sunday of March. Nevertheless, in the United States, DST starts on the second Sunday of March. Also, the time when the shift occurs differs from country to country. Some regions forward the clocks in the middle of the night at 01:00 am or 02:00 am local time. This practice signifies the arrival of the spring and lasts till the Autumn. Meanwhile, the return to the standard time takes place in October or November.
Keep in mind the process of changing time and recall it easily!
Mnemonics are short but memorable phrases that help to memorize better certain things1.
In the case of the Daylight Saving Time, English speaking people usually use a catchy mnemonic “spring forward, fall back.” It makes sense since the verb spring refers to the forwarding movement and the verb fall implies right the opposite which is a backward movement2.
DST around the world
Countries on Standard Time Zone only
Considering that DST is the widely applicable practice in the world, some countries developed their own rules and terminology for this occurrence. In particular, the countries which do not follow DST live in the Winter Time Zones (Standard Time Zone). Among the most popular countries which do not observe DST are the following:
- The United Arab Emirates
- North Korea
- South Korea
- Most recently Brazil (since 2019)
- Tunisia (since 2009)
Countries on DST only
Some countries considered not to switch their clocks again, but instead of implementing a Standard Time Zone, they opted for staying on summer hours all year round. Nowadays the countries that observe this type of measure are Argentina, Belarus, Russia[^3], Saskatchewan, Yukon, Iceland, Kyrgyzstan, Malaysia, Morocco3, Namibia, Singapore, Turkey, Turkmenistan and Uzbekistan.
Countries on standard time and DST
And, as we know, a lot of countries use Standard Time Zone alternating it with DST during certain periods of the year. In the table below are shown the dates of the beginning and the end of Daylight Saving Time in the majority of these countries:
|Africa||Egypt||Last Friday in April||Last Thursday in September|
|Canary Islands||Last Sunday in April||Last Sunday in October|
|Asia||Most states of the former USSR||Last Sunday in March||Last Sunday in October|
|Iraq||First Friday in April||Last Friday in October|
|Israel||Last Friday before April 2||The Sunday between
Rosh Hashana and Yom Kippur
|Jordan||Last Thursday of March||Last Friday in September|
|Mongolia||Fourth Friday in March||Last Friday in September|
|Palestinian regions||First Friday on or after 15 April||First Friday on or after 15 October|
|Syria||March 30||September 21|
|Australasia||Australia - South Australia, Victoria,
Australian Capital Territory, New South Wales,
Lord Howe Island
|First Sunday in October||First Sunday in April|
|Australia - Tasmania||First Sunday in October||Last Sunday in March|
|New Zealand, Chatham||Last Sunday in September||First Sunday in April|
|Tonga||First Sunday in November||Last Sunday in January|
|Europe||European Union||Last Sunday in March at 1 am UTC||Last Sunday in October at 1 am UTC|
|UK||Last Sunday in March at 1 am UTC||Last Sunday in October at 1 am UTC|
|North America||\\[The United States](/United-States/time), Canada (excluding Saskatchewan and parts of Quebec, B.C., and Ontario),
Bermuda, St. Johns, Bahamas, Turks and Caicos
|Second Sunday in March||First Sunday in November|
|Cuba||Third Sunday in March||Last Sunday of October|
|Greenland||Last Sunday in March at 1 am UTC||Last Sunday in October at 1 am UTC|
|Mexico (except Sonora)||First Sunday in April||Last Sunday in October|
|South America||Chile||October 11||March 29|
|Falklands||First Sunday on or after 8 September||First Sunday on or after 6 April|
|Paraguay||Third Sunday in October||Second Sunday in March|
|Uruguay||First Sunday in October||Second Sunday in March|
Flipped usage of DST in Morocco
But not only energy saving can be the reason to use DST. For example, Morocco and Western Sahara, which have permanent daylight saving time implemented, due to the certain specifics of Muslim culture, make a short exception every year during Ramadan and it is a time when they switch their clocks to the Standart Time Zone4.
Time change process in different parts of the world
The time change process affects in a different way distinct parts of society. For example, industrialized communities don’t experience that much of a difference since they follow the same schedule throughout the year. For people who have a regular job or have to attend educational institutions like kindergartens, schools, universities, etc, their timetable stays the same during the whole year. Contrariwise, an agrarian society totally depends on solar time and it is mostly conducted by the actual duration of the daylight. In this case, it will change seasonally and will vary according to the part of the world. In some places, like tropics in the North and South, in summer daylight will remain longer than in winter, because of the specifics of the Earth rotation and position towards the sun.
For the majority of the population who keep the same routine throughout the year, resetting clocks means that they will have more time for other activities after they are finished with the work or studying since they had to start their day sooner by waking up one hour earlier. It sounds good and many people find this practice to be reasonable. Nonetheless, it also supposes to begin the day in the darkness during the winter because of having one less hour in the morning which makes this measure questionable for some people.
Although the change of the times of sunrise and sunset is relatively even during the seasons' change, Daylight Saving Time supporters claim that this way they have more time after their daily work routine and they would rather wake up earlier to take advantage of the longer daylight afterward. They also claim this measure helps to reduce energy use because of longer days, so the need for lighting and heating is lower as well. But the actual results show that this statement is not totally correct.
But if we go further from the North and South tropics, we will see that the change of the daylight duration is more noticeable and less equal. As an example, countries on the Arctic Circle don't experience that much of a difference with the DST practice. Therefore, for countries like Iceland or Denmark, the day will stay short anyway, since the sunrise is much later and the sunset is early in comparison to the countries from other latitudes that are higher. The solar time differs drastically from Standard Time. DST also isn’t very useful for the places around the equator because the variation of the daylight throughout the year is insignificant5.
On this map by Stefano Maggiolo areas where local time is behind solar time are in red.
Useful tips for drivers
To make the transition from wintertime to summertime easier and safer and avoid possible accident, we suggest going to bed earlier and waking up at the same time, working out, and finally — don’t staring at smartphone screen in the evening!
🚗 Read more about how to ease into Daylight Saving Time if you’re a driver →
Common synonyms and the correct way to spell DST
DST abbreviation stands for Daylight Saving Time and it is used to define the practice when we advance our clocks one hour ahead. The other variation is Daylight Savings Time with the “s.” This way of spelling DST isn’t completely correct but considering its wide and quite frequent use around the world, it became acceptable.
Other common variants of Daylight Saving Time are daylight time, daylight savings, and DST. In Italy, the practice is called ora legale, which means “legal time.” In British English, the most common expression for this term is Summertime6.
How many people in the world spell DST incorrectly and why?
Although the correct way of spelling DST is Daylight Saving Time, the majority of people around the world would use Savings. We are talking about a large part of people from Canada, the USA, Australia, India and some European countries, including the UK and France.
The correct way of spelling this term is more common in some Asian countries such as Vietnam, Japan, and Philippines and amongst European countries like Germany, Italy and Netherlands.
The correct way of spelling DST is Daylight Saving Time because the point is the saving of daylight, that’s why it seems correct for it to be Daylight Saving Time, not Daylight Savings Time. (We are not talking about multiple savings.) The singular is the original form and seems to be the standard. However, it’s common for the plural form to be used. Savings is often used when the fact of the time change is mentioned by the media or in casual conversation. And sometimes Savings is even seen on calendars.
Current influence of DST around the world
The most inconvenient time zones
In nowadays reality, it would be very complicated to rearrange our lives around a day length that is continually changing every day. Instead of that, the clocks and watches show us a mean time that is based on the length of the actual solar day averaged throughout the whole year. This is commonly referred to as the mean solar day and its length is 24 hours. There are two reasons for the actual solar day to differ in length from day to day: first of all, the orbit of the Earth around the Sun is an ellipse and not a perfect circle.
Consequently, the distance from the Earth to the Sun usually alters throughout the year. (The Earth is the closest to the sun in January and the furthest — in July). And the second reason is related to the axis about which the Earth rotates. The thing is that it is tilted the way that the height of the Sun in the sky at local noon alterations throughout the year – high in the summer and low in winter. These two factors conspire to alter the apparent speed with which the Sun moves across the sky at different times of the year, altering the day length7.
As a result, some parts of the world don’t have an even length of day and night when at some places the sunrise and sunset times hardly vary. For example, it is a case of Kenya which is situated right on the equator. This country never implemented a DST but the solution was shifting from one time zone to another.
Or another example could be countries that occupy large territories. For example, in the United States, there are 14 states that officially straddle two time zones 12 months of the year due to the practicalities of having standard time close to solar time or of localities keeping the same time as larger population centers not far across the border8.
But in China, it’s even more complicated. In 1949 Baijin was declared as a new capital and became the nation’s time center of the country. From five time zones before the revolution, China became just one. As a result, for some parts of the country, the day begins too late and lasts for a very long time. Some regions even established their own time which isn’t official but results to be more convenient9.
DST history around the world
The concept of increasing daylight time has been relevant since the ancient civilizations. Namely, the Romans employed different types of time measures to increase the activities during the most productive hours of daylight10. Unlike modern people, ancient civilizations were more flexible and could easily switch to the required time.
Eventually, the more developed idea to maximize the efficiency of people during the daylight was proposed by Benjamin Franklin. Later, the influential politician Winston Churchill also advocated implementing this concept. It would allow people to be more productive during daylight and could be an effective decision to save energy11.
First implementations on the national level
During the First World War, in 1916, Kaiser Wilhelm was the first leader who decided to enable DST because he recognized that increasing the hours of daylight nationwide would benefit the energy consumption and health of people and soldiers in particular.
After Germany, many other European adopted the Daylight Saving Time due to its perceived benefits for the population and energy efficiency.
The United States joined the format of DST
Along with the adoption of the Standard Time Act of March 19, 1919, in the United States, the first time DST was implemented was at 02:00 am on March 31 in the same year. On this day, people were asked to stop their clocks for one hour. The return to the standard time was scheduled in seven months.
However, following the World War, this practice was criticized by the population and politicians of the United States. Although DST became optional for the areas, the major part of the country proceeded to use it till today. Only several areas decided to opt-out from DST because it was not suitable due to the climate conditions.
The benefits of Daylight Saving Time
A craving to encourage energy saving and reduce electric lighting was, and still remain, as an initial reason for implementing such a thing as Daylight Saving Time. Some of the estimates suggest that this measure can help to reduce energy use around the country for at least 0.5%. A lot of studies were conducted to prove these results and some of them were based on different systems of measuring data and complex simulations. At the same time, there are just as many studies that show the opposite effect of implementing DST and claim that there is no noticeable benefit from this practice or even argue that the results are actually worse if the fuel consumption is taken into account. Although, it is proven that it definitely helps to reduce energy and heating usage in the evening, but it most likely results in higher demand for gasoline and electricity during the dark and cold mornings.
Apart from that, besides the development of new technologies and alternative energy resources, our pattern of energy use and most of the equipment we use on a daily basis have changed significantly since the majority of these studies were conducted12.
Also, from the point of view of the safety on the road, some studies claim that the greatest benefits from daylight saving time are for pedestrians during the period between the beginning of the springtime change and just after the fall time change. However, the benefits are smaller during the darkest winter months because the PM reduction is increasingly offset by increases during the AM as sunrise gradually occurs later and later, eventually entering the morning rush hours. For vehicle occupants, the reduction in fatal crashes is lower and relatively constant throughout the winter13.
DST in Europe
With the historical adoption of DST in Germany, other countries recognized the positive effects of this practice. In particular, it was evident that people would benefit from the extra hour of daylight while using less energy. As a result, the majority of the European countries adopted DST as the annual tradition.
The decision to start using DST among the state members of the European Union was impacted by the European Commission which issued the directives on how to implement it. In 1981, the Commission along with the European Economic and Social Committee started the regulation and provided suggestions regarding the positive effects of DST14.
Subsequently, these legislative bodies constantly study the effectiveness of this practice and how it benefits the citizens. Also, the organizations collect the data from the studies and public opinion to determine whether any amendments to DST are needed.
Public opinion on DST
Since the adoption of DST, many people have expressed their concerns regarding the implications of sudden changes in the biorhythm. Since citizens and members of parliament reconsidered their attitudes towards DST and asked to make changes, multiple public hearings were organized.
The most important hearing was organized in 2015 with a discussion on how to rework summertime or cancel it altogether. Moreover, the citizens criticize DST and appeal to the EU summertime agreements. As a result, the European Parliament often receives public petitions on this subject with the proposition to change the procedures of DST.
DST in the United States
The population and scientists express criticism concerning the effectiveness of DST in the United States. In particular, the primary argument remains to be the fact that the benefits of increasing daylight were relevant only during times of low technological development. Energy conservation is no longer effective with the increase of daylight hours.
The shifts of the clocks affect the dairy farmers because it is difficult for cows to change the biorhythm. As a result, this issue negatively contributes to their ability to produce milk. Subsequently, DST is considered to have a negative impact not only on the human sleep cycle but also on the productivity of agriculture.
The critics emphasize that electricity conservation is actually worse or not noticeable during DST. For example, the study in Indiana state indicated the greater use of air-conditioning systems15. Therefore, the gain from the lighting savings is lower than the losses from the functioning of other appliances.
Which states do not observe DST
Although the United States accepted the use of DST for the country, there are several exceptions. Namely, Hawaii decided not to implement DST due to the notion that during the year, the daily sunlight cycle is the same. Similarly, the U.S territories like the Virgin Islands, Puerto Rico, Guam, and American Samoa also do not require DST due to the same reasons. In this regard, one may admit that the areas which are located near the equator do not benefit from the extra hour of daylight.
Nevertheless, the state of Arizona has unique attitudes towards DST. The state decided not to follow the tradition of daylight saving and yet the Navajo Reservation which is located on the territory of the state does set clocks one hour forward. Considering the climate and extremely hot temperature during the summer months, the additional hour of daylight is more damaging than effective for the population of Arizona. Therefore, the residents of the state actually would appreciate even fewer daylight hours during
Evolution of the DST remain the same through the time
In the beginning, DST was about saving energy and reducing the use of electricity and lightning because of the dark evenings. However, the latest studies show that nowadays DST doesn’t help to reduce the use of electricity. Moreover, it would increase the consumption of other resources such as gas and fuel16.
The possible reason to keep DST differs a lot from the initial motive. It was noticed that consumers are more likely to go on shopping after a working day if the light is still outside. Also, it encourages them for other social activities, in particular, golf, barbeque, gyms and going to the restaurants17.
Countries that abandon DST and their reasons
From the beginning, the main reason for introducing Daylight Saving time was to save energy consumption, but in reality, it doesn’t make that much of a difference since saved energy in the evening results in higher use of electricity during the dark mornings and increases fuel usage.
This issue was mentioned by Marita Ulvskog, a member of the European Parliament from Sweden who wrote the transport and tourism committee’s draft resolution on discontinuing seasonal time changes.
In March, the European Union voted against keeping the Daylight Savings in 2021. Clocks should be adjusted on the final Sunday of March 2021 or the final Sunday of October 2021 depending on whether it is preferred to stay in summer or wintertime18. Moreover, a lot of experts are concerned that over time, the bright morning light is eliminated by Daylight Saving Time and has a negative influence on biological clocks, which can lead to increased risk of heart attack and ischaemic stroke, as well as other unfavorable effects of partial sleep deprivation.
Countries that consider abandoning DST
Some of the countries that observe DST are still considering whether they should end this practice or not.
For example, in British Columbia, scientists from different institutions expressed their concerns about keeping Daylight Saving time practice in an Open Letter to the BC Government in Support of Permanent Standard Time. They insisted that it has a negative impact on health and shouldn’t be implemented anymore19.
Likewise in the United States, a lot of states recently have applied for changes to daylight saving, and a few states, including Oklahoma, Texas, and Kansas have bills in progress to opt out of the time change completely. This option would require the state to stay on standard time permanently throughout the year. Then Florida passed a bill as well. The state expressed a will to set its clocks on permanent daylight saving time as well if it is approved by the federal government20.
New Zealand observes DST as well, but it seems that some people disagree with this and would rather change it to a Standard Time. There is even a movement called “Take Back The Clocks” which describes DST as “disruptive, unnatural, and unnecessary”21.
Consequences of the end of the Daylight Savings system
It is impossible to claim whether established only standard time or summertime is the best option for everybody. Both of them have their pros and cons. The European Commission conducted a survey which has shown that the majority of the citizens would prefer to keep summertime throughout the year. In this case, the main advantage was to leave work and school during daylight and enjoy the sunlight afterward without any switching from one time to another during the year22.
Furthermore, with the uninterrupted summertime implemented, the rate of traffic accidents most likely would drop down since people would return to their homes after exhausting work during the daylight.
In the case of Spain, besides removing the need to reset their clocks, this would permit the country to adopt the most relevant geographical time zone, which would be the Greenwich meridian.
On the other hand, specifically in the case of Spain, some parts would be affected if this measure was implemented. For example, in some autonomous communities like Galicia, the light wouldn’t reach them until 9:30 am. It causes some complications for the human body since it is more natural for us to do daily activities when there is a light outside.
It should also be noted that our resting time is affected when it gets dark later. It is amazing to be able to enjoy more hours of sunlight, but it also means that the time of going to bed will be postponed. As a result, we will be more tired when we will have to wake up for school or work, as the time for getting up will remain the same. All of this can lead to a recession in our productivity and make our performance worse.
The reasons for some countries to reintroduce DST back
In the early 1930s, Mexico implemented Daylight Saving Time but it lasted only for a season. Later, in 1939 it was brought back due to a power shortage in a period of severe drought and lack of water for hydroelectric plants. This continued for much of the next 20 years and probably was the main reason for DST from 9 December 1940, about two months into the dry season, until 1 April 1941.
Another Interesting case is Tunisia which first had daylight saving on 15 April 1939, and start and end dates in the war years were the same as France since that area was a French protectorate. The other exception was for eight days in 1943 when Tunisia reverted to Standard Time. The reason wasn’t Ramadan as it was in September. A likely explanation was that the Allies wanted earlier dawn times during a period of heavy fighting with German and Italian troops. After that, the government would implement it for some years because of Ramadan, the energy consumption didn’t seem to show much of a difference.
A couple of times it was used and pulled back in Haiti with the purpose to save energy in 2005, 2012 and 2015 until 11 March 2016 when the Haitian government led by a new president Jocelerme Privert canceled this measure8.
Organizations steering time policy and standards around the world
The system of worldwide time zones was developed by Sanford Fleming back in 1878 but it is still used nowadays. His idea consisted in dividing the world into 24 time zones, giving each part 15º space. The concept came from the fact that the Earth is round and its rotation lasts approximately 24 hours. So this way, the whole surface of the planet would be divided into 24 “slices” each, or 15º because it is what we get if we divide 360 by 24.
However, later it was discovered that Earth’s speed of rotation is slowly going down so there had to be made some adjustments. This is how almost 100 years later, in 1964, was developed a new time scale (UTC) or coordinated universal time. The Daylight Saving Time isn’t taken into account and doesn’t affect it in any way since this new measuring system is completely based on the speed of the Earth’s rotation and its position. The start point is considered to be Greenwich meridian23.
This coordinated time scale is maintained by the Bureau International des Poids et Mesures (BIPM). The BIPM is an international organization established by the Metre Convention, through which all the Standards related to the time measuring are discussed and implemented on the worldwide level24.
The International Earth Rotation and Reference Systems Service (IERS) is the institution responsible for maintaining global time and reference frame standards, notably through its Earth Orientation Parameter (EOP) and International Celestial Reference System (ICRS) groups25.
Nowadays “Official Time” or “legal time” is that prescribed by the law or decree of a sovereign national authority within its own jurisdictional boundaries, which means that every government has a capacity to establish their official time according to the laws that are in force26.
DST in popular culture
Like anything that has an undeniable impact on our lives, Daylight Saving Time forms an important part of people’s routine around the world. As a result, it is mentioned more and more often in the entertainment industry as well.
People share on the Internet the issues they have experienced because of the DST and funny stories that have happened to them, posting on their social media and creating memes.
And not only this but our favorite TV shows would reflect the reality we are facing at the moment, and make us laugh at it. For example, in the TV show Veep, in one of the episodes, Jonah's (the main character) inability to understand Daylight Saving Time causes him problems at work but ultimately gives him a bill to champion. The episode contained a lot of funny moments related to the issues caused by DST.
Also, there are people who don’t believe in coincidences and always search for a rational explanation for everything. As an example, in 2005 President George W. Bush extended daylight-saving time as part of a long-term solution to the nation's energy problems. The new law extended daylight-saving time by four weeks - beginning three weeks earlier and ending one week later. But some people believed that saving energy wasn’t the main reason for this change, but selling more candies could as with the new dates of DST, the night of Helloween got 1 hour longer therefore, more candies could be sold.
Candy is a big business: The U.S. confectionery industry raked in $33.6 billion in sales around 2014, and the industry is expected to hit nearly $40 billion by 2019, according to Candy Industry. And it's no secret that Halloween is a huge time of year for candy manufacturers and distributors.
However, there is a rumor that candy companies lobbied for a long time to push back the end of daylight saving time, allegedly even putting little candy-filled pumpkins on every senator's chair back in 1986. But it is just a rumor and its legitimacy has been debated, but it's fun to think about.
Berthold (1918). "Daylight saving in ancient Rome". The Classical Journal. 13 (6): 450–451. ↩
David S. Prerau (2005). “Saving the Daylight: Why We Put the Clocks Forward”, Granta Books. ISBN 978-186207796 ↩
Effect of daylight saving time on lighting energy use: A literature review, Institute for Research in Construction, National Research Council, 1200 Montreal Road, Building M24, Ottawa, Canada K1A 0R6 ↩
Communication from the commission to the Council, the European Parliament and the European economic and social committee under Article 5 of Directive 2000/84/EC on summer time arrangements”, European Commission. 23 November 2007 ↩