By Jueseppi B.
Daylight Saving Time – often referred to as “Summer Time”, “DST” or “Daylight Savings Time” – is a way of making better use of the daylight in the evenings by setting the clocks forward one hour during the longer days of summer, and back again in the fall.
Daylight saving time (DST)—also summer time in several countries in British English, and European official terminology—is the practice of advancing clocks so that evenings have more daylight and mornings have less. Typically clocks are adjusted forward one hour near the start of spring and are adjusted backward in autumn.
The modern idea of daylight saving was first proposed in 1895 by George Vernon Hudson and it was first implemented during the First World War. Many countries have used it at various times since then. Although most of the United States used DST throughout the 1950’s and 1960’s, DST use expanded following the 1970’s energy crisis and has generally remained in use in North America and Europe since that time.
The practice has been both praised and criticized. Adding daylight to evenings benefits retailing, sports, and other activities that exploit sunlight after working hours, but can cause problems for evening entertainment and other occupations tied to the sun. Although an early goal of DST was to reduce evening usage of incandescent lighting (formerly a primary use of electricity), modern heating and cooling usage patterns differ greatly, and research about how DST currently affects energy use is limited or contradictory.
DST clock shifts present other challenges. They complicate timekeeping, and can disrupt meetings, travel, billing, record keeping, medical devices, heavy equipment, and sleep patterns. Software can often adjust computer clocks automatically, but this can be limited and error-prone, particularly when DST protocols are changed.
Justification and rationale
As modern societies operate on the basis of “standard time” rather than solar time, most people’s schedules are not governed by the movements of the earth in relation to the sun. For example, work, school and transport schedules will generally begin at exactly the same time at all times of the year regardless of the position of the sun. However, in non-equatorial regions the total number of hours of sunlight in a day will vary a great deal between winter and summer. As a result, if “standard time” is applied year round, a significant portion of the longer sunlight hours will fall in the early morning while there may still be a significant period of darkness in the evening.
Because many people will tend to sleep in the early morning hours, these hours of sunlight are wasted for them, whereas if they are shifted to the evening via DST, they can then be used. As days shorten again in autumn/winter, sunrises get later and later, meaning that people could then be waking up and spending a significant portion of their mornings in the dark, so clocks are then returned to the “standard” time. In theory, people who need to or want to could simply wake up earlier to take advantage of the sunlight then, but this is impractical because of the inflexibility of clock-based schedules.
The actual effects of DST can vary significantly by location depending on its latitude and position relative to the center of its time zone. For example, DST does not have much practical effect in extremely northern or southern locations because the very long/short days mean that the artificial manipulation of time has little or no real impact on daily life since sunrise/sunset times are already dramatically out of sync with modern working hours. DST is also of no use for locations near the equator because they see only a very small variation in daylight through the year.
Although not punctual in the modern sense, ancient civilizations adjusted daily schedules to the sun more flexibly than modern DST does, often dividing daylight into twelve hours regardless of day length, so that each daylight hour was longer during summer. For example, Roman water clocks had different scales for different months of the year: at Rome‘s latitude the third hour from sunrise, hora tertia, started by modern standards at 09:02 solar time and lasted 44 minutes at the winter solstice, but at the summer solstice it started at 06:58 and lasted 75 minutes. After ancient times, equal-length civil hours eventually supplanted unequal, so civil time no longer varies by season. Unequal hours are still used in a few traditional settings, such as some Mount Athos monasteries and all Jewish ceremonies.
During his time as an American envoy to France, Benjamin Franklin, publisher of the old English proverb, “Early to bed, and early to rise, makes a man healthy, wealthy and wise”, anonymously published a letter suggesting that Parisian seconomize on candles by rising earlier to use morning sunlight. This 1784 satire proposed taxing shutters, rationing candles, and waking the public by ringing church bells and firing cannons at sunrise. Franklin did not propose DST; like ancient Rome, 18th-century Europe did not keep precise schedules. However, this soon changed as rail and communication networks came to require a standardization of time unknown in Franklin’s day.
Modern DST was first proposed by the New Zealand entomologist George Vernon Hudson, whose shift-work job gave him leisure time to collect insects, and led him to value after-hours daylight. In 1895 he presented a paper to the Wellington Philosophical Society proposing a two-hour daylight-saving shift, and after considerable interest was expressed in Christchurch, New Zealand, he followed up in an 1898 paper. Many publications incorrectly credit DST’s proposal to the prominent English builder and outdoorsman William Willett, who independently conceived DST in 1905 during a pre-breakfast ride, when he observed with dismay how many Londoners slept through a large part of a summer’s day.
An avid golfer, he also disliked cutting short his round at dusk. His solution was to advance the clock during the summer months, a proposal he published two years later. The proposal was taken up by the Liberal Member of Parliament (MP) Robert Pearce, who introduced the first Daylight Saving Bill to the House of Commons on 12 February 1908. A select committee was set up to examine the issue, but Pearce’s bill did not become law, and several other bills failed in the following years. Willett lobbied for the proposal in the UK until his death in 1915.
Starting on 30 April 1916, Germany and its World War I allies were the first to use DST (German: Sommerzeit) as a way to conserve coal during wartime. Britain, most of its allies, and many European neutrals soon followed suit. Russia and a few other countries waited until the next year and the United States adopted it in 1918.
Broadly speaking, Daylight Saving Time was abandoned in the years after the war (with some notable exceptions including Canada, the UK, France, and Ireland for example). However, it was brought back for periods of time in many different places in the coming decades, widely during the Second World War. It became widely adopted, particularly in North America and Europe starting in the 1970.s as a result of the 1970’s energy crisis.
Since then, the world has seen many enactments, adjustments, and repeals. For specific details, an overview is available at Daylight saving time by country
Although daylight saving time is considered to be correct, daylight savings time (with an “s”) is commonly used. The form daylight saving time uses the present participle saving as an adjective, as in labour saving device; the first two words are sometimes hyphenated, as in daylight-saving time. The common variants daylight savings time and daylight savings use savings by analogy to savings account. Daylight time is also common. Willett’s 1907 proposal used the term daylight saving, but by 1911 the term summer time replaced daylight saving time in draft legislation in Britain, and continental Europe uses similar phrases, such as Sommerzeit in Germany, zomertijd in Dutch, horario de verano or hora de veranoin Spain and l’heure d’été in France, whereas in Italy the term is ora legale, that is, legal time (legally enforced time) as opposed to “ora solare”, solar time, in Winter.
The name of local time typically changes when DST is observed. American English replaces standard with daylight: for example, Pacific Standard Time (PST) becomes Pacific Daylight Time (PDT). British English calls UK time British Summer Time (BST), and typically inserts summer into other time zones, e.g. Central European Time (CET) becomes Central European Summer Time (CEST). Abbreviations do not always change: for example, many (though not all) Australians say that Eastern Standard Time (EST) becomes Eastern Summer Time (also EST). In Australia it is also called EDT (Eastern Daylight Time)
Permanent daylight saving time
A move to “permanent daylight saving time” (staying on summer hours all year with no time shifts) is sometimes advocated, and has in fact been implemented in some jurisdictions such as Iceland, Russia, and Belarus. The United Kingdom stayed on daylight saving time from 1968 to 1971. Advocates cite the same advantages as normal DST without the problems associated with the twice yearly time shifts. However, many remain unconvinced of the benefits, citing the same problems and the relatively late sunrises, particularly in winter, that year-round DST entails.
“Permanent daylight saving time” or permanent summer time are perhaps misnomers, as the practice essentially becomes the “standard time” for the area. However, it can be considered to be a deviation from the internationally agreed timezone of the Coordinated Universal Time system.
Many jurisdictions such as Argentina, Central China, Georgia, Kazakhstan, Central Mongolia, Saskatchewan, Senegal, Sudan, Turkmenistan, and Tokelau can be considered to use a form of de facto permanent daylight saving time because they use time zones located to the east of the time zones they are geographically located in. Thus their local times are later than the time they would theoretically occur under a “pure” system, such as the nautical time system, giving the same effect as year-round DST.
More about Daylight Saving Time
- Transitioning into Daylight Saving Time
- Daylight Savings Time vs Daylight Saving Time
- Spring Forward, Fall Back and Similar Expressions
- Health Solutions to Swing to Daylight Saving Time
- The Never-ending Daylight Saving Debate
- Upcoming Daylight Saving Time Clock Changes
- List of countries that observe Daylight Saving Time in 2013
- The World Clock – Current time all over the world