A map showing countries that use daylight saving according to each hemisphere as of September 2019^[update].

  DST in the northern hemisphere summer

  DST in the southern hemisphere summer

  DST no longer used

  DST never used

Clocks are advanced by one hour during the very early morning at the beginning of DST.

When DST ends, clocks are set back (as if to repeat one hour) during the very early morning. Specific times vary.

Daylight saving time (DST) or summer time (ST) is a time to time keep during summer. During the summer months, the sun stays 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.

DST helps stores that sell to people after they get off work, and it doesn't hurt 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:

• United States: most of Arizona and Hawaii
• Australia: Queensland, Western Australia and the Northern Territory
• Canada: Saskatchewan except for a few locations with the border with Alberta and Manitoba, and the Yukon Territory

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

US dates and UK Time

Since 1971 all clocks in the European Union, of which the UK is a member state, have changed on same dates and at the same time, 06:00 GMT.^[1][2]

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"Should we change the clocks?". National Farmers Union. Mar 18, 2010. Archived from the original on Mar 30, 2010. Retrieved Sep 23, 2015.

Automatic adjustment

Some computers connected to the Internet will automatically adjust their clocks for DST. Most newer 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.