Daylight Saving Time is the legal time that States set during the summer with the intent of saving energy . It results from increasing the schedule used the rest of the year by one hour. With this change, both sunrise and solar noon and sunset occur at a later (legal) time. The change is usually made during the early morning on some day in the spring indicated by the administration. In the fall , the change is reversed and legal time approaches solar time .

When it was proposed, the objective of this measure was to reduce the time between sunset and the moment in which the majority of the population goes to sleep ; assuming that the latter is set to legal time. This reduction in the time spent at night should imply a reduction in energy consumption for lighting . This saving is possible only in the summer of the temperate zones , in which the days are longer and it is possible to start human activities with daylight despite the change in legal time.

The legal time change during the summer was proposed and advocated by William Willett between 1907 and 1914. This was first widely employed during World War I , to save coal .

By the year 2022, the summer time change is used in most of the United States , Canada , in the northern border strip of Mexico , Europe (with the exception of Russia and Belarus ), Chile , Paraguay , Cuba , Bahamas , Haiti and some Oceanian countries . In the rest of the world, most countries do not use it.

Origin

Some ancient civilizations, such as the Egyptians, Romans, and Mesopotamians, adjusted their hours to the sun more flexibly than daylight saving time does, usually dividing daylight time into twelve hours of equal length (temporary hours ) , for so daylight hours were longer during the summer. ^1 2 For example, Roman hourglasses had different scales for different months of the year: at Rome’s latitude , the third hour after sunrise, tertia , began (using modern time) at 09:02 and lasted 44 minutes on the solsticewinter, but in the summer it started at 06:58 and lasted 75 minutes. 3

In the  fourteenth century , the mechanical clock was invented, which allowed the application of the 24-hour system of equal duration, more useful for calculations than had already been invented by Hipparco de Nicaea in the [[  2nd century  BC. C.|II century a. C.]] 1

In 1784, the American politician and scientist Benjamin Franklin , during his service as a foreign envoy to France, anonymously published a letter stating that Parisians saved candlelight by getting up earlier, thus using more sunlight. ⁴ It was first published in the ” Economie ” section of the Journal de Paris newspaper . The revised version in English is called “An Economic Project”, ⁵ a title that Franklin did not give it. ⁶ Franklin’s moderate satire proposed imposing a tax on shutters, rationing the sails and waking the citizens ringing the church bells and firing cannons at dawn, according to his proverb:

” Early to bed and early to rise / Makes a man healthy, wealthy, and wise “

Franklin was proposing to change customs, not legal time.

In the  18th century , Europe did not have precise timetables. This soon changed, however, as the railroad and communication networks necessitated the standardization of time in a way that was not known in Franklin’s day. ⁸ Before taking that step, in 1810 an example of seasonal adaptation of the activity was given in Spain; The regulation of the Cortes of Cádiz included, in its article 2, the schedule of sessions and in it a change of time was dictated in May and in October equivalent to the modern time change:

“The president will open the sessions at ten from October 1 to April 30 and at nine from May 1 to September 30.”

Therefore, the time was not changed but the schedule. ⁹ ​10

In 1905 the English builder William Willett conceived of daylight saving time during a pre-breakfast horse ride, when he was surprised to think how many Londoners slept through the best part of a summer day. ¹¹ Very fond of golf , he disliked shortening his course at twilight. Two years later he published his proposal, ¹² But his idea was not immediately implemented.

Daylight saving time, which was applied for the first time on April 30, 1916 by Germany , its allies and its occupied areas during the First World War . The United Kingdom , most of the rest of the Warring States, and many neutral European countries followed. The USSR and a few other nations waited the following year, and the United States did not use it until 1918. Since then there have been many proposals, adjustments, and reversals. 13

In Mexico , daylight saving time was implemented for the first time during the six-year term of Ernesto Zedillo , on April 7, 1996, with the aim of making the most of sunlight. 14

Politics 

Daylight saving time has caused controversy since it was first implemented. Its supporters argue, in the words of Winston Churchill , that it helps “increase the chances of finding health and happiness among the millions of people who live in this country”, referring to the United Kingdom . His critics “detect the bony, bluish hand of Puritanism ^, eager to put people to bed earlier and get them up earlier, to make them healthier, wealthier, and wiser in spite of themselves.” ¹⁶ Historically, retailers, athletes, and tourists have come out in favor of daylight saving time, while farmers and the entertainment industry have opposed it.

The fate of Willett’s 1907 proposal shows many political interests involved. The proposal attracted many supporters, including Balfour , Churchill , Lloyd George , MacDonald , Edward VII of England (who employed half-hour daylight saving time at Sandringham ), the director of Harrods , and the manager of the National Bank. However, the opposition was stronger: it included Prime Minister Asquith , Christie (the Astronomer Royal ), George Darwin , Napier Shaw (director of the Met Office), many farm organizations and theater owners. After many hearings, the proposal was narrowly defeated in a 1909 UK Parliament vote . Willett’s allies made similar proposals every year from 1911 to 1914, without success. ¹⁷ The United States was even more reluctant: United States Representative Andrew Peters of Massachusetts proposed daylight saving time in May 1909, but the idea failed in committee. 18

The First World War changed the balance of support, as daylight saving time was proposed to alleviate the harshness of the war in terms of saving coal and night blackouts to make bombing difficult. Following its implementation by the German Empire , the United Kingdom first applied daylight saving time on May 21, 1916. ¹⁹ Retail and manufacturing interests, led by Pittsburgh industrialist Robert Garland, soon they began to lobby for the passage of daylight saving time. The entry into the war of the United States in 1917 provided the reasons to overcome the objections, and from 1918 daylight saving time was applied. 20

The war ended and returned to unbalance the balance. Farmers still disagreed with daylight saving time, and many countries revoked it after the war. The United Kingdom was an exception: it continued with daylight saving time but for years adjusted transition dates for various reasons, including special rules during the 1920s and 1930s to prevent time changes on Easter mornings . ²¹ The United States was more conventional: Congress overturned it in 1919. President Woodrow Wilson vetoed the repeal twice, but his second veto of his was overridden, ²²and only a few cities in the country preserved local daylight saving time. 23

Wilson’s successor, Warren G. Harding , opposed daylight saving time as a “hoax.” Reasoning that people should get up and go to work earlier in the summer, he ordered federal employees in Washington, DC, to start work at 08:00, not 09:00, during the summer of 1922, and left for private companies to decide if they wanted to follow suit. Some of them did, but some didn’t, leading to a mess that critics gave names like ” Daylight Slaving Time “; ^24 25 The experiment was not repeated. 26

Since Willett, the world has seen many similarly politically motivated DST proposals, adjustments, and repeals. ²⁷ In the United Kingdom, the outdoor sports and leisure industry supports the Single/Double Summer Time (SDST – ) proposal, a variant in which one hour is advanced in winter and two in summer. ²⁸ In the United States, the Sporting Goods Manufacturers Association and the National Association of Convenience Stores lobbied for and extended daylight saving time in 2007; ²⁹ in the mid -1980s ,Clorox and 7-Eleven sponsored a coalition to support the 1987 extension, and Idaho senators voted for it because they thought it would lead to more fast-food restaurants selling more Idaho fries . 30

Between July 4 and August 16, 2018, the European Commission held a public consultation with the citizens of the European Union about summer time and its possible abolition at Union level. 4.6 million people participated in the consultation, of which 80% were in favor of abolishing the biannual time change, with a preference for maintaining summer time as permanent time.30

Between July 4 and August 16, 2018, the European Commission held a public consultation with the citizens of the European Union about summer time and its possible abolition at Union level. 4.6 million people participated in the consultation, of which 80% were in favor of abolishing the biannual time change, with a preference for maintaining summer time as permanent time.

Advantages and disadvantages 

The proposal made by Willett in 1907 ensured that daylight saving time increased the opportunities to practice outdoor leisure activities during the evening daylight hours. Obviously this does not change the length of the day: the longer days around the summer solstice at high latitudes lead to a shift in daylight hours from morning to afternoon so that morning light is not wasted. 12

According to Thomas C. Schelling , the general agreement of the population on the schedule to be followed is more advantageous than the adoption of summer time individually. According to this consideration, an individual would obtain a greater advantage when the entire population follows summer time than if he decided to get up earlier, since coordination provides a great benefit. 31

However, many ignore daylight saving time and alter their schedules to coordinate with sunlight, or with distant colleagues. ³² Daylight saving time is not used during winter because mornings are darker: workers may not have free time with sunlight and children would have to go to school when the sun has not yet risen. 33

Adding daylight time in the afternoons benefits commerce , sports practice and other activities that are favored by the presence of light after the workday, ³⁰​ The increase in evening light can help reduce traffic accidents , ³⁴ but its effects on health and the incidence of crime are less clear. Daylight saving time is said to save electrical energy by reducing the need for artificial lighting, ³⁵ but the supporting evidence is weak, ³³ as daylight saving time can stimulate the appearance ofdemand peaks , which increases costs. 36

On the other hand, time changes make it difficult to perceive time and can cause sleep problems for people, as well as disrupt meetings, travel, baggage check-in, record-keeping, medical device and heavy machinery use. ³⁷ Many computer- run systems are capable of adjusting their clocks automatically, but errors do occur, especially when daylight saving time rules change. 38

Energy use 

By delaying the nominal time at dawn and dusk, the use of artificial light is increased in the morning and reduced in the afternoon. As Franklin’s satire pointed out, energy is saved if the evening saving exceeds the morning increase, which can happen if people need more light in the afternoon than in the morning. However, no significant statistical evidence has been found to support this hypothesis. The United States Department of Transportation concluded in 1975 that daylight saving time can reduce electricity consumption by 1 percent during March and April, ³⁵ but the National Institute of Standards and Technologyreviewed the Department of Transportation study in 1976 and found no indication of significant energy savings. ³³ In 2000, when parts of Australia began using daylight saving time in late winter, electricity consumption did not decrease, but both the morning peak power consumption and prices increased. ³⁶ In the United States there is no clear evidence that electricity was saved by the extension of daylight saving time that was introduced in 2007, 39 ^and although one utility reported a decrease in March 2007, five others did not. they did it. ⁴⁰​ The use of summer time can increase the consumption ofGasoline : In the United States, demand for gasoline grew by 1 percent in March 2007. ⁴¹ The closer a country is to the equator , the less justified is the time change, since the length of the days is more similar in winter and in summer. Of course, there are divided countries: a schedule for each zone.

In Spain, a study carried out by the IDAE (Institute for the Diversification and Saving of Energy) in 2011 found a saving of 5% in the consumption of domestic electricity during the months with summer time. 42

Economic effects 

Retailers , manufacturers of sports equipment and other businesses benefit from the increase in light in the afternoon, as it encourages their customers to go shopping and practice outdoor sports. For example, in 1984 Fortune magazine estimated that a seven-week extension of DST would bring an additional $30 million to 7-Eleven stores . The National Golf Foundation estimated that the extension would increase industry revenue by $ 200 million to $300 million . ⁴³ On the other hand, summer time can harm farmers and other activities whose work is determined by the sun. For example, theGrain harvesting is done when the dew evaporates, so when farmers arrive earlier in the summer their labor is less valuable . ⁴⁴ Daylight saving time also hurts audience rates for prime-time shows . ⁴⁵ Theaters and cinemas are also affected , especially drive-ins . 46

Time changes have a certain correlation with a decrease in economic efficiency. In 2000 daylight saving time led to an estimated loss of $31 billion in the stock market. ⁴⁷ Time changes and summer time have a direct economic cost, since they entail extra work to carry out meetings and harm computerized activities. For example, the change in the start and end dates of daylight saving time in the United States, Canada , and New Zealand in 2007 caused IT problems, as systems had to be updated to deal with this unforeseen event. 48

Public safety 

In 1975, the US Department of Transportation reported that traffic accidents during daylight saving time had been reduced by 0.7 percent, and estimated that the real reduction would be between 1.5 and 2 percent, ³⁵ but in 1976 a study by the Standards Institute found no evidence to support these conclusions. ³³ In 1995 the Insurance Institute for Highway Safety estimated that there had been a 1.2 percent reduction, and a 5 percent reduction in fatal pedestrian collisions. ³⁴ Others have found similar reductions. ⁴⁹ In the United Kingdom it is planned to apply theSingle/Double Summer Time (SDST) to reduce traffic accidents by 3 to 4 percent compared to normal summer time. ⁵⁰ It is not clear whether sleep disruption contributes to fatal accidents immediately after jet lag. A correlation between time changes and accidents was observed in the United States, but not in Sweden . If this biannual effect exists at all, it is much less than the overall reduction in accidents. ⁵¹ ​52

In the 1970s, the US Law Enforcement Assistance Administration (LEAA) found a 10 to 13 percent reduction in violent crime in Washington, DC , during the 1970s. summer schedule. However, the LEAA did not filter out other factors, examining only two cities and concluding that crime had dropped in only one of them and only in certain crime categories. The Department of Transportation stated that “it is impossible to conclude with certainty that equivalent benefits can be found throughout the country.” ⁵³ Although daylight makes potential victims feel safer, this can encourage crime. ⁵⁴​

An indirect benefit of schedule changes is taking advantage of them as a reminder for semi-annual maintenance tasks. In many countries, firefighters encourage citizens to use daylight savings as a reminder to replace batteries in smoke and carbon monoxide detectors . This is especially important in the fall, just before heater season, when fire is most likely. Other biannual tasks include reviewing fire exits and familiarization with emergency plans, inspecting vehicle lights, searching storage areas for hazardous materials, and reprogramming thermostats . ⁵⁵ ​56⁵⁷ However, it is not an essential function of daylight saving time, and areas without daylight saving time may also use early spring and fall as reminders. 58

In March 2020, the Israeli government planned to delay daylight saving time to discourage gatherings during the COVID-19 pandemic. However, it was decided that this would be too technically difficult to implement in such a short time. 59

Complexity 

Time changes have the clear disadvantage of complexity. People must remember to change the schedule. Those who frequently cross time zone boundaries have to keep track of different DST rules, as not all places have the same ones. The length of the day becomes variable. Lack of coordination occurs frequently in meetings, travel, billing and registration systems, which can be expensive. ⁶⁰ In the vicinity of the autumn transition from 03:00 to 02:00, a clock shows the period from 02:00 to 03:00 twice, which can lead to confusion. 61

Computerized systems may require a period of inactivity or a reboot when the time changes. Ignoring this requirement damaged a steel mill in 1993. ³⁷ Medical devices can have problems that harm patients, without it being obvious to hospital staff that they need to remain vigilant. ⁶² These problems are compounded when daylight saving time rules change, as occurred in 2007 in the United States. Software developers must test and possibly modify programs, and users must install updates and restart applications. 38

Some time changes can be avoided by adjusting clocks continuously ⁶³​ or at least more gradually—for example, Willet originally suggested using 20-minute transitions per week—but this added complexity has never been applied.

Daylight saving time can increase the disadvantages of standard time . For example, when reading a sundial, daylight saving time must be taken into account in addition to time zone and natural discrepancies . ⁶⁴ In addition, daylight saving time complicates time-dependent recommendations for avoiding sun exposure . 65

Transfer of energy expenditure 

A winter schedule (outside the holiday period) in which there would be many hours without sunlight in the morning, would transfer energy expenditure (and therefore economic cost) to industry and other labor sectors, which is where a large part of the population in the morning. Even so, it must be taken into account that the business world sometimes uses permanent lighting and independently of the exterior light.

On the other hand, there is lighting that is turned on between sunset and sunrise, such as street lamps that illuminate streets and highways. In this case, they are on for less time in summer than in winter. But this saving is not due precisely to the time change, but to the fact that during the summer there are more hours of natural light.

On the other hand, the winter schedule (in which the weight of the hours without sunlight rests basically on the afternoon; that is, when the majority of the population leaves work) transfers the energy expenditure to the population.

Health 

Daylight saving time has several effects on health. In societies with fixed working hours, it provides more evening light for exercise in the open air. Alter sun exposure; but the question of whether it is beneficial or not depends on the person’s location and time, since sunlight triggers the synthesis of vitamin D in the skin. Sunlight strongly influences winter depression . Daylight saving time can help in cases of depression , causing people to get up earlier, ⁶⁶ but some claim otherwise. ⁶⁷ The Foundation Fighting Blindness(Foundation Against Blindness), an organization chaired by magnate Gordon Gund that fights blindness, managed to extend daylight saving time in 2005, 2930 ^but this can also harm those suffering ^from nyctalopia . ⁶⁸ On the other hand, it has been found that the Monday following the start of summer time, there is a notable increase in heart attacks; and conversely, these are reduced when the winter time is returned. 69

Daylight saving time reduces sleep duration and efficiency, ⁷⁰ and the Kazakhstan government cited health problems due to daylight saving time as the main reason for abolishing daylight saving time. 71

Diversity in your application

The typical implementation of daylight saving time is during the early morning of a day indicated by the administration. It begins on a spring day that is moved forward one hour. This implies that there is a day that has 23 hours. On an autumn day you go back an hour, and that hour repeats itself.

Time changes are typically scheduled on a weekend night to mitigate disruption. One-hour changeovers are most common, but Australia’s Lord Howe Island uses half-hour changeovers. ⁷² In the past, twenty-minute and two-hour shifts have been used.

Coordination strategies differ when adjacent time zones change time. The European Union changes time at the same time, at 01:00 UTC ; for example, Eastern European Time is always one hour ahead of Central European Time . ²¹ Most of North America changes time at 02:00, so adjacent areas do not change simultaneously. For example, Mountain Time may momentarily be zero or two hours ahead of Pacific Time.. Districts in Australia go further and do not always agree on DST start and end dates; for example, in 2006 Tasmania moved its clocks forward on October 1, Western Australia on December 3, and the rest of the daylight saving time zones on October 29. 73

Start and end dates may differ with location and year. Since 1996, European summer time has been applied from the last Sunday in March to the last Sunday in October; before the rules were not uniform in all the states of the United States . ²¹ As of 2007, most states in the United States and Canadian provinces and territories apply daylight saving time from the second Sunday in March to the first Sunday in November. ⁷⁴ The change in 2007 was part of the Energy Policy Act of 2005; Previously, from 1987 to 2006, the start and end dates were the first Sunday in April and the last Sunday in October, and Congress will be able to return to the earlier dates once a study on energy use has been completed. ⁷⁵ In Mexico , daylight saving time was adopted nationwide in 1996 (before it was only applied in the state of Baja California) with the same start and end dates as its neighbors to the north, the United States and Canada: from the first Sunday in April to the last Sunday in October. However, when those countries changed their start and end dates in 2007, the Mexican government refused to change theirs to match those of neighboring countries, despite the lag this would cause. In 2010, the border cities with the United States again requested the change, and the Congress of the Unionde México decided to patch the corresponding decree; Thus, an arbitrary border strip of 20 kilometers was established, and the start and end dates of summer time were modified only in that region, with which it was shifted to the border of the rest of the country, instead of making the change on a scale national. Since then, Mexico is the only country on the planet that has two different summer time applications. In 2015, it was once again proposed to the Mexican Congress that all of Mexico, and not just its northern border, make its daylight saving time coincide with its northern neighboring countries.

The proposal was rejected by Congress on June 29, 2016, this being the third refusal in a decade, until its abolition in 2022, where the state of Baja California, as well as the border cities that already applied the time change on the same dates as the United States are once again the only ones to use it.

The start and end dates are reversed in the southern hemisphere . For example, in Chile until 2010 summer time was applied from the second Sunday in October to the second Sunday in March, whereas from 2012 a new summer time is applied, which will be from the 28th April of each year until September 1 of the same year with transitions at 00:00. ⁷⁶ The time difference between the United Kingdom and Chile can therefore be three, four or five hours, depending on the time of year. ⁷⁷ However, since January 28, 2015, the Chilean government headed by Michelle Bachelet, announced that it will remain permanently in summer time, definitively going from GMT -4 to GMT -3. ⁷⁸ As of 2016, winter time is again implemented, beginning in May and ending in August. 79

Western China , Iceland , and other areas are west of their ideal time zone, so it’s like they have daylight saving time all year. For example, Saskatoon , Saskatchewan , is at 106°39′W longitude, slightly west of the center of the ideal Mountain Time Zone ( 105 °W), but Saskatchewan is in Central Standard Time (90° O) all year, so it is always about 67 minutes ahead of solar time . ⁸⁰ The United Kingdom and Irelandthey piloted daylight saving time throughout the year from 1968 to 1971, but abandoned it because of its unpopularity, especially in the northern regions. 81

The west of France , Spain and other areas have the time zone changed and also apply summer time, so the effect is to have summer time in winter and an extra hour in summer. The same is true in other zones, such as Nome , Alaska , it is at 165°24′W longitude, which is west of the center of the Central Samoan Time zone (165°W), but is on Alaska time. (135°W) with daylight saving time DST, so it is slightly more than two hours ahead in winter and three in summer. 82

Daylight saving time is not normally used near the Equator , as sunrise and sunset times do not vary enough to warrant it. Some countries use it only in some regions; for example, southern Brazil uses it (in 2019, DST was completely abolished in Brazil), while equatorial Brazil does not. ⁸³ Only a minority of the world’s population uses summer time, as Asia and Africa in general do not. By 2022 , the last country in the Americas that eliminated Daylight Saving Time was Mexico , when on October 26 , the Senateratified the decision to end said schedule by October 30 of that year. 84

Computer science 

Most computer systems can automatically change the time when daylight saving time changes. The two most widely used implementations today are zoneinfo and Microsoft Windows .

Zoneinfo 

The zoneinfo database assigns a name to the historical and predictable time changes in a region. This database is used by many computer programs, including most Unix operating systems , Java Oracle ; ⁸⁵ HP ‘s “tztab” database is similar but incompatible. ⁸⁶ When authorities change the DST rules, zoneinfo updates are installed as part of regular operating system maintenance. On Unix systems the TZ environment variable of a process specifies the name of the place, such as in TZ='America/New_York'.

Older systems may use only the TZ values ​​required by POSIX , which specify at most one start and end time in their value. For example, TZ='EST5EDT,M3.2.0/02:00,M11.1.0/02:00'specify North American time starting in 2007. TZ must be changed when daylight saving time rules change, and the new value of TZ applies to all years, affecting old dates as well. 87

Microsoft Windows 

The process for adjusting and updating daylight saving time settings in Microsoft Windows varies with each version. ⁸⁸ ​Windows Vista and Windows 7 can have at least two start and end rules for each time zone. In a Canadian winter time zone, a Vista setup does not have problems with times from 1987-2006 and after 2006, but may have problems with earlier. Older Microsoft Windows systems can store only one boot and one rule for each zone, so the same Canadian zone will only be free for dates after 2006. 89

These limitations have caused problems. For example, prior to 2005, DST in Israel varied each year, and in some it did not apply. Windows 95 had the correct rules only for 1995, so it caused problems for all other years. In Windows 98 Microsoft gave up and marked Israel as not having daylight saving time, so Israelis had to manually change the time twice a year. Israel’s 2005 Daylight Savings Law made predictable rules, but Windows couldn’t represent the dates in the rule so they weren’t dependent on the year. Some partial solutions may be to change the timezone files every year ⁹⁰​ and there is a tool from Microsoft that does this automatically.91

Notes and references 

Bibliography 

• Ian R. Bartky; Elizabeth Harrison (1979). “Standard and daylight-saving time” . Scientific American 240 (5): 46-53. ISSN  0036-8733 .
• Michael Downing (2005). Spring Forward: The Annual Madness of Daylight Saving Time . Shoemaker & Hoard. ISBN  1-59376-053-1 . Archived from the original on 2007-06-30 . Retrieved May 16, 2007 .
• David Prerau (2005). Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time . Thunder’s Mouth Press. ISBN  1-56025-655-9 . Retrieved May 16, 2007 .
• The UK-focused English version is Saving the Daylight: Why We Put the Clocks Forward . Granta Books. ISBN  1-86207-796-7 . Retrieved May 16, 2007 .