Wednesday, 25 July 2012

Day Light Saving - “spring forward, fall back”

Daylight saving time (DST)also summer time in several countries, 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.Although not used by most of the world's countries,daylight saving time is common in the Northern Hemisphere's northern latitudes.

      DST observed
     DST formerly observed
      DST not observed.

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 autumn/winter and spring/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". People could simply wake up earlier to take advantage of the sunlight then, but this is impractical because of the inflexibility of clock-based schedules.
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 a typical case where a one-hour shift occurs at 02:00 local time, in spring the clock jumps forward from the last moment of 01:59 standard time to 03:00 DST and that day has 23 hours, whereas in autumn the clock jumps backward from the last moment of 02:59 DST to 02:00 standard time, repeating that hour, and that day has 25 hours.
Most of the United States sets Daylight Saving Time at 2:00 a.m. on the second Sunday in March and reverts to standard time on the first Sunday in November. In the U.S., each time zone switches at a different time.
In the European Union, Summer Time sets and ends at 1:00 a.m. Universal Time (Greenwich Mean Time). It sets the last Sunday in March and ends the last Sunday in October. In the EU, all time zones change at the same moment.
So now daily in Summer when clock will show 8 its actually 7 (according to Std time) and this way that 1 hr light will be utilized. and from starting of winter clock again will be back to std. time.

Enjoy the DST Timing shifts in Non-Observing Countries
Get your cellphone.
Change its timezone to any state that observe DST,say Newyork state of US.
Now set date manually from your settings->Set Date/Time.
Now observe the difference between time from November to March and March to November.
Time from November to March is standard time i.e. GMT-5 while time from March to November is one hour ahead from standard time.
I am afraid, It works on some phones… :) 

Why observe DST?
Many countries observe DST, and many do not. Many countries use DST to make better use of the daylight in the evenings. The extra hour of daylight in the evening is said to give children more social time and can boost the tourism industry because it increases the amount of outdoor activies.
DST is also used to save energy and reduce artificial light needed during the evening hours.
DST's clock shifts have the obvious disadvantage of complexity. People must remember to change their clocks. However Software can often adjust computer clocks automatically, but this can be limited and error-prone, particularly when DST protocols are changed.

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