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Daylight Saving Time – DST

Illustration image

Fall back: Clocks go back 1 hour in the fall.

©iStockphoto.com/karen roach

Daylight Saving Time – often referred to as "Summer Time", "DST" or "Daylight Savings Time" – is a way of making better use of the daylight in the evenings by setting the clocks forward one hour during the longer days of summer, and back again in the fall.


Clocks back or forward?

The clock moves ahead (= losing one hour) in the spring when DST starts, and falls back one hour (= gaining one hour) when DST ends in the fall. To remember which way the clock goes, keep in mind one of these sayings: spring forward, fall back or “spring ahead, fall behind.”

Northern Hemisphere

Many countries in the northern hemisphere observe DST, but not all. Daylight saving time begins in the northern hemisphere between March–April and ends between September–November. Standard time begins in the northern hemisphere between September–November and ends between March–April.

Southern Hemisphere

When do the Clocks Change next? (upcoming DST changes worldwide)

Daylight saving time begins in the southern hemisphere between September–November and ends between March–April. Standard time begins in the southern hemisphere between March–April and ends between September–November. Many countries in the southern hemisphere may observe DST.

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. Many people believe that DST could be linked to fewer road accidents and injuries. 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 activities.

DST is also used to save energy and reduce artificial light needed during the evening hours — clocks are set one hour ahead during the spring, and one hour back to standard time in the autumn. However, many studies disagree about DST's energy savings and while some studies show a positive outcome, others do not.

It is difficult to predict what will happen with Daylight Saving Time in the future. The daylight saving date in many countries may change from time to time due to special events or conditions.The United States, Canada and some other countries extended DST in 2007. The new start date is the second Sunday in March (previously the first Sunday in April) through to the first Sunday in November (previously the last Sunday in October).

Brief history of DST

Benjamin Franklin first suggested Daylight Saving Time in 1784, but modern DST was not proposed until 1895 when an entomologist from New Zealand, George Vernon Hudson, presented a proposal for a two-hour daylight saving shift to the Wellington Philosophical Society.

The conception of DST was mainly credited to an English builder, William Willett in 1905, when he presented the idea to advance the clock during the summer months. His proposal was published two years later and introduced to the House of Commons in February 1908. The first Daylight Saving Bill was examined by a select committee but was never made into a law. It was not until World War I, in 1916, that DST was adopted and implemented by several countries in Europe who initially rejected the idea. There is more information about the history of DST on our website.

Is DST always one hour ahead of standard time?

Today it is almost always one hour ahead, but throughout history there have been several variants on this, such as half adjustment (30 minutes) or double adjustment (two hours), and adjustments of 20 and 40 minutes have also been used. A two-hour adjustment was used in several countries during the 1940s and elsewhere at times.

A half adjustment was sometimes used in New Zealand in the first half of the 20th century. Australia's Lord Howe Island (UTC+10:30) follows a DST schedule in which clocks are moved 30 minutes forward to UTC+11, which is Australian Eastern Daylight Time (AEDT) when it is on DST.

Sometimes DST is used for a longer period than just the summer, as it was in the United States during World War II. From February 3, 1942 to September 30, 1945 most of the United States had DST all year; it was called “War Time.”

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