The Pros and Cons of Daylight Saving Time
Ever since the very first time Daylight Saving Time (DST)* was introduced about 100 years ago, people have disagreed about whether setting the clocks one hour forward in the spring and back again in the fall has the desired effect. In a few countries, DST has become a political power struggle, while others debate whether setting the clocks one hour ahead in the spring has the intended effect of conserving energy or reducing road accidents.
Daylight saving time (DST) or summer time is the practice of advancing clocks during summer months by one hour so that evening daylight lasts an hour longer, while sacrificing normal sunrise times. Typically, regions with summer time adjust clocks forward one hour close to the start of spring and adjust them backward in the autumn to standard time.
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 Parisians economize 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. (Despite common misconception, Franklin did not actually propose DST)
Modern DST was first proposed by the New Zealand entomologist George Hudson who spent his leisure time to collect insects, which led him to value after-hours daylight
An Englishman, William Willett 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. His solution was to advance the clock during the summer months. His proposal was taken up by a Member of Parliament (MP) who introduced the first Daylight Saving Bill to the House of Commons on February 12, 1908. A select committee was set up to examine the issue, but the bill did not become law, and several other bills failed in the following years.
Several European countries started using Daylight Saving Time during the First World War, which lasted from July 1914 until November 1918. It was introduced by Germany and its ally Austria-Hungary as a way to conserve coal during wartime.
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 during the following decades, and commonly during the Second World War. Hitler’s commanders imposed German time as they moved through Europe but it did not always work. The French initially resisted DST at the beginning of the war, but by 1941 they were officially on “Hitler time”. Some French patriots, however, stuck to the old French time, 2 hours behind the Berlin-based DST.
DST was also implemented in the aftermath of World War II mainly to help people conserve fuel for national recovery and rebuilding programs. However, many European countries later abandoned Daylight Saving Time, as it became a reminder of the war itself and the humiliation of foreign occupation. Both the Italians and the French repealed DST after clearing up the debris of German occupation.
It became widely adopted, particularly in North America and Europe starting in the 1970s as a result of the 1970s energy crisis Today, most countries in Europe follow a synchronized DST schedule that lasts from the last Sunday of March to the last Sunday of October
DST is generally not observed near the equatorwhere sunrise times do not vary enough to justify it. Some countries observe it only in some regions; for example, southern Brazil observes it while equatorial Brazil does not. Only a minority of the world’s population uses DST because Asia and Africa generally do not observe it.
In some Muslim countries DST is temporarily abandoned during Ramadan(the month when no food should be eaten between sunrise and sunset), since the DST would delay the evening dinner.
Over 70 countries use DST today, mainly to:
- Make better use of natural daylight.
- Conserve energy otherwise spent on artificial light.
- Decrease road accidents by making sure roads are naturally lit during the hours with most traffic.
The practice has both advocates and critics. Putting clocks forward benefits retailing, sports, and other activities that exploit sunlight after working hours.
Supporters of DST generally argue that it saves energy, promotes outdoor leisure activity in the evening (in summer), and is therefore good for physical and psychological health, reduces traffic accidents, reduces crime, or is good for business. Groups that tend to support DST are urban workers, tourism operators, and others who benefit from increased light during the evening in summer. Also retailers, outdoor sports enthusiasts and businesses benefit from extra afternoon sunlight, as it induces customers to shop and to participate in outdoor afternoon sports.
Studies link DST to reduced road injuries. A joint Transport Research Laboratory and University College of London study predicted that fewer people would be killed and injured in road accidents if one hour of daylight was transferred from the morning to the afternoon.
The tourist industry welcomes DST, claiming that the extra hour of sunlight makes people stay out later, thus spending more money on activities like festivals, shopping and concerts.
Opponents argue that clock shifts increase the risk of heart attack by 10 percent and disturb sleep and reduce its efficiency. Effects on seasonal adaptation of the circadian rhythm can be severe and last for weeks because DST disrupts the body clock. Children may feel tired and irritable for several days after an hour’s change in their bedtime routines
Studies show that there is an increase in road accidents on the days after clocks are set forward one hour in the spring, and that being tired can decrease productivity, concentration, and general well-being.
Several studies have suggested that actual energy savings due to the reduced need for lighting and heating are inconclusive, and that DST increases motor fuel consumption.
It can cause problems for outdoor activities tied to sunlight, such as farming. For instance traditional dairy farmers often protest that changing the clocks one hour twice a year makes milking cows and getting the milk collected in time a challenge. In more modern dairy farms, the cows are milked at will by robots but farmers in developing countries are still an active part of the debate. Furthermore cows are sensitive to the timing of milking, so delivering milk earlier disrupts their systems.. Also farmers oppose DST because grain is best harvested after dew evaporates, so when field hands arrive and leave earlier in summer their labor is less valuable.
DST also hurts prime-time television broadcast ratings, drive-ins and other theatres.
DST has mixed effects on health. In societies with fixed work schedules it provides more afternoon sunlight for outdoor exercise. However it alters sunlight exposure; whether this is beneficial depends on one’s location and daily schedule, as sunlight triggers vitamin D synthesis in the skin, but overexposure can lead to skin cancer.
* The form daylight savings time (with an “s”) is much more common than the older form daylight saving time in American English. In Britain, Willett’s 1907 proposal used the term daylight saving time, but by 1911 the term summer time replaced it. Continental Europe uses similar phrases, such as Sommerzeit in Germany, , horario de verano or hora de verano in Spain and 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 North American mnemonic “spring forward, fall back” (also “spring ahead , fall behind”) helps people remember which direction to shift clocks.