Daylight saving time: Why do some countries change their clock timings?

Several countries like the United States, Canada and Cuba are preparing to set their clocks back by an hour on Nov 5. It is because of a custom known as daylight saving time or simple daylight time, and in some countries like the United Kingdom, it is known as summer time.

Amid this, the debate has once again emerged in the US whether this practice should be followed or not. But what exactly is daylight saving time? Here’s what we know:

What is daylight saving time (DST)?

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It is a practice of advancing clocks, typically by one hour, during warmer months so that darkness falls at a later clock time.

Usually, to implement DST, clock timings are changed in two ways. In late winter or spring, the clocks are set forward by one hour, known as ‘spring forward’. In autumn, clock timings are set back by one hour to return to standard time, known as ‘fall back’.

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Most of North America and Europe follow this custom, while the majority of countries elsewhere, especially those close to the equator, do not.

When does daylight saving time end?

DST will end on Nov 5 in the United States and its neighbouring countries at 2:00 am local time. To end DST, all the clocks will be simply turned back by an hour. It started on Mar 12 when clocks were turned forward in North America by an hour at 2:00 am local time.

The UK and the European Union countries have already ended their DST on Oct 29. Usually, DST starts on the second Sunday of March and ends on the first Sunday of November in North America.

Countries that practice DST

Most of North America and Europe, including the US, Canada and Cuba follow this practice. However, not all states and territories in the US follow DST. Exceptions include Hawaii and most of Arizona – except for most of the Navajo Nation – which do not observe daylight saving time. American Samoa, Guam, the Northern Mariana Islands, Puerto Rico and the Virgin Islands also observe permanent standard time.

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The United Kingdom practices daylight savings. Australia also changes its clockson the first Sunday of October. However, many countries worldwide have adopted and rejected it multiple times.

In March, Egypt announced that it would reintroduce DST after seven years to rationalise energy. Japan also considered adopting it for the 2020 Olympics but later rejected it due to technical challenges.

(With inputs from agencies)