Daylight saving time

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A map showing countries that use daylight saving according to each hemisphere as of September 2016.      DST in the northern hemisphere summer      DST in the southern hemisphere summer      DST no longer used      DST never used
A map showing countries that use and do not use daylight saving as of September 2016.      DST used      DST no longer used      DST never used
Diagram of a clock showing a transition from 02:00 to 03:00
Clocks are advanced by one hour during the very early morning at the beginning of DST.
Diagram of a clock showing a transition from 03:00 to 02:00
When DST ends, clocks are set back (as if to repeat one hour) during the very early morning. Specific times vary.

During the summer months, the sun stays is visible for a longer time, and sunset happens late in the day. For this reason, certain countries advance the time by one hour near the start of summer, and put it back one hour during autumn. The time during summer is called Daylight saving time (DST). In Europe it is called summer time. The time during the winter months is called "standard time".

DST helps stores that sell to people after they get off work, but it hurts farmers and others whose hours are set by the sun. It cuts traffic accident rates. Sometimes it can reduce energy costs, but it can also increase them.

Most of the world's countries do not use DST, but it is common in Europe and North America.

The United States, Australia, the United Kingdom, Canada and many other countries have DST. These countries also have regions that do not have DST:

Iceland, Russia, Ukraine and Belarus are countries in Europe without DST.

USA dates and UK dates[change | change source]

Since 1996 all clocks in the European Union, of which the UK is a member state, have changed on same dates and at the same time, 01:00 GMT.[1]

  • British Summer Time starts: Last Sunday in March
  • British Summer Time ends: Last Sunday in October
  • British Summer Time clocks change at 01:00 (1.00 am) Greenwich Mean Time (GMT).
  • USA 2013 date: March 10
  • USA 2012 date: March 11
  • USA 2011 date: March 13
  • USA 2010 date: March 14
  • USA 2009 date: March 8
  • USA 2008 date: March 2

Permanent GMT+1[change | change source]

Permanent Summer Time has support in some northerly countries such as the UK. It was tried in the British Standard Time experiment, with Britain remaining on GMT+1 throughout the year. This took place between 27 October 1968 and 31 October 1971.

There are proposals for GST+1 in the winter, and double summer time (GST+2) in the winter. In favour are most city dwellers: children do not have to come home after school in the dark, and late afternoon and early evening activities benefit. In favour also were those concerned with accidents, because both accidents and fuel consumption go down.[2][3]

Against are many farmers in northerly latitudes, because sunrise would occur in winter at about 10.00 in the morning. However, in March 2010 the National Farmers Union said that it was not against Single/Double Summer Time, and is in fact relatively neutral, with many farmers expressing a preference for the change.[4]

Automatic adjustment[change | change source]

Most computers, mobile phones and other devices connected to the Internet will automatically adjust their clocks for DST. Some older computers will not adjust or will adjust the time incorrectly or on the wrong date. Also, computers with more than one operating system may be incorrectly adjusted twice or more when each operating system boots.

References[change | change source]