what is the meaning of the sqving time daylight?

Answer 1

save energy

Answer 2

The main purpose of Daylight Saving Time (called "Summer Time" in many places in the world) is to make better use of daylight. We change our clocks during the summer months to move an hour of daylight from the morning to the evening. Countries have different change dates. Glide your cursor over the map to see how changing the clocks affects different latitudes.

If you live near the equator, day and night are nearly the same length (12 hours). But elsewhere on Earth, there is much more daylight in the summer than in the winter. The closer you live to the North or South Pole, the longer the period of daylight in the summer. Thus, Daylight Saving Time (Summer Time) is usually not helpful in the tropics, and countries near the equator generally do not change their clocks.

A poll conducted by the U.S. Department of Transportation indicated that Americans liked Daylight Saving Time because "there is more light in the evenings / can do more in the evenings." A 1976 survey of 2.7 million citizens in New South Wales, Australia, found 68% liked daylight saving. Indeed, some say that the primary reason that Daylight Saving Time is a part of many societies is simply because people like to enjoy long summer evenings, and that reasons such as energy conservation are merely rationalizations.

However, Daylight Saving Time does save energy. Studies done by the U.S. Department of Transportation show that Daylight Saving Time trims the entire country's electricity usage by a small but significant amount, about one percent each day, because less electricity is used for lighting and appliances. Similarly, in New Zealand, power companies have found that power usage decreases 3.5 percent when daylight saving starts. In the first week, peak evening consumption commonly drops around five percent.
Energy use and the demand for electricity for lighting homes is directly related to the times when people go to bed at night and rise in the morning. In the average home, 25 percent of electricity is used for lighting and small appliances, such as TVs, VCRs, and stereos. A good percentage of energy consumed by lighting and appliances occurs in the evening when families are home. By moving the clock ahead one hour, the amount of electricity consumed each day decreases.

In the summer, people who rise before the sun rises use more energy in the morning than if DST was not in effect. However, although 70 percent of Americans rise before 7:00 a.m., this waste of energy from having less sunlight in the morning is more than offset by the savings of energy that results from more sunlight in the evening.

In the winter, the afternoon Daylight Saving Time advantage is offset for many people and businesses by the morning's need for more lighting. In spring and fall, the advantage is generally less than one hour. So, Daylight Saving Time saves energy for lighting in all seasons of the year, but it saves least during the four darkest months of winter (November, December, January, and February), when the afternoon advantage is offset by the need for lighting because of late sunrise.

In addition, less electricity is used because people are home fewer hours during the "longer" days of spring and summer. Most people plan outdoor activities in the extra daylight hours. When people are not at home, they don't turn on the appliances and lights.

There is a public health benefit to Daylight Saving Time, as it decreases traffic accidents. Several studies in the U.S. and Great Britain have found that the DST daylight shift reduces net traffic accidents and fatalities by close to one percent. An increase in accidents in the dark mornings is more than offset by the evening decrease in accidents.

Opposition to Daylight Saving

Many people intensely dislike Daylight Saving Time. Frequent complaints are the inconvenience of changing many clocks and adjusting to a new sleep schedule. For most people, this is a mere nuisance, but some people with sleep disorders find this transition very difficult. Indeed, there is evidence that the severity of auto accidents increases and work productivity decreases as people adjust to the time change.

Some argue that the energy savings touted by DST is offset by the energy used by those living in warm climates to cool their homes during summer afternoons and evenings. Similarly, the argument can be made that more evening hours of light encourage people to run errands and visit friends, thus consuming more gasoline.

Protests are also put forth by people who wake at dawn, or whose schedules are otherwise tied to sunrise, such as farmers. Canadian poultry producer Marty Notenbomer notes, "The chickens do not adapt to the changed clock until several weeks have gone by, so the first week of April and the last week of October are very frustrating for us."

In Israel, ultra-Orthodox Sephardic Jews have campaigned against Daylight Saving Time because they recite Slikhot penitential prayers in the early morning hours during the Jewish month of Elul.

Some countries set their clocks to fractional time zones. For example, Kathmandu, Nepal is 5:45 hours ahead of Universal Time, and Calcutta (Kolkatta), India is 5:30 ahead. This is not an attempt to compromise and have half Daylight Saving Time year-round, but rather an adjustment made because the countries straddle international time zones.

Idea of Daylight Saving Time

The idea of daylight saving was first conceived by Benjamin Franklin (portrait at right) during his sojourn as an American delegate in Paris in 1784, in an essay, "An Economical Project." Read more about Franklin's essay.

Some of Franklin's friends, inventors of a new kind of oil lamp, were so taken by the scheme that they continued corresponding with Franklin even after he returned to America.

The idea was first advocated seriously by London builder William Willett (1857-1915) in the pamphlet, "Waste of Daylight" (1907), that proposed advancing clocks 20 minutes on each of four Sundays in April, and retarding them by the same amount on four Sundays in September. As he was taking an early morning a ride through Petts Wood, near Croydon, Willett was struck by the fact that the blinds of nearby houses were closed, even though the sun was fully risen. When questioned as to why he didn't simply get up an hour earlier, Willett replied with typical British humor, "What?" In his pamphlet "The Waste of Daylight" he wrote:

"Everyone appreciates the long, light evenings. Everyone laments their shortage as Autumn approaches; and everyone has given utterance to regret that the clear, bright light of an early morning during Spring and Summer months is so seldom seen or used."