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Daylight Saving Time (DST)

Daylight Saving Time (DST) is the practice of turning the clock ahead as warmer weather approaches and back as it becomes colder again so that people will have one more hour of daylight in the afternoon and evening during the warmer season of the year. (Some believe that it should be called Daylight Shifting Time because no daylight is actually "saved.") Daylight Saving Time varies somewhat from country to country. Countries in equatorial and tropical climates do not observe Daylight Saving Time. The months when the clock is set ahead and back differ between northern and southern hemispheres.

The U.S. Energy Policy Act of 2005 mandated changes to Daylight Saving Time, extending it three weeks earlier in the spring and one week later in the fall. Starting March 11, 2007 clocks spring ahead an hour on the second Sunday in March and fall back on the first Sunday in November. The assumption behind the change was that it would decrease the need for artificial light sources and, as a result, save energy.

As reported by, many admins are waiting until the last minute to patch systems . Time discrepancies could cause scheduling and synchronization problems for unpatched operating systems, applications and devices. Indirectly, those changes may also affect not only systems in these areas but also any systems that interact with them. To address the issue, Microsoft and other software makers issued Daylight Saving Time patch es.

Here are a few of the world's variations in observing Daylight Saving Time:

  • In most of North America, clocks are set forward one hour on the second Sunday in March and back on the first Sunday in November.
  • The state of Arizona in the U.S. does not observe Daylight Saving Time. However, the large Navajo Reservation in northeastern Arizona does observe it.
  • In non-equatorial Brazil, DST starts the first Sunday in November and ends the third Sunday in February.
  • In the European Union, DST starts the last Sunday in March at 1 am UTC and ends the last Sunday in October at the same time.
  • In Russia, the clock is set ahead beginning the last Sunday in March at 2 am local time and set back the last Sunday in October at the same time. Because the clock is already set an hour ahead of standard time, Russians effectively have two more hours of daylight in the summer.
  • In Israel and the area of Palestine, Daylight Saving Time is observed, but the time of change is decided every year. Israel and the Authority of Palestine sometimes have different start and end dates.
  • Jordan has Daylight Saving Time all year.
  • Australia's DST starts the last Sunday in October and ends the last Sunday in March. However, Tasmania's DST starts the first Sunday in October along with New Zealand and ends the last Sunday in March. New Zealand ends the third Sunday in March.
This was last updated in March 2011

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Thanks for the nice article.

Note in Australia DST is determined by the states and not all states implement DST or implement the same dates. For example along the east coast (one timezone in winter), we have Victoria and NSW who are in synch, Tasmania who run DST to different dates as mentioned above, and Queensland who doesn't have daylight savings.


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