What is Daylight Saving Time?

Beginning of autumn marks many changes such as cooler weather, shorter days, and leaves changing colour. But for many people across the world it means the end of Daylight Saving Time. On November 6 this year, Daylight Saving Time (DST) ended in several countries.

Idea behind DST

DST is the practice of moving the clocks forward one hour from the Standard Time during the summer months and then changing them back during the fall. In the U.S., it always begins on the second Sunday in March and ends on the first Sunday in November.

The idea behind the clock shift is to increase daylight time in the Northern Hemisphere, as days lengthen in spring and shorten in autumn.

In the days when coal was very much in use, DST was implemented to maximise the limited daylight hours. It is believed that by springing forward and falling back, people add an hour of sunlight to the end of the work day.

In countries in the Northern Hemisphere, clocks are usually set ahead one hour in late March or in April and are set back one hour in late September or in October.

On the first Sunday of November, at 2 a.m., clocks in most of the U.S. and many other countries turn back an hour on what is called standard time and stay there for nearly four months. On the second Sunday of March, at 2 a.m., clocks move forward one hour back to DST.


This system was earlier used in train schedules. It was later put into practice in Australia, Europe, and the U.S. to save fuel and power by reducing the need for artificial light during World War I by extending daylight time.

The U.S. standardised it by passing the Uniform Time Act of 1966. However, the States are not required by the law to “fall back” or “spring forward”. Hawaii and most of Arizona do not observe the DST.

Benjamin Franklin is the earliest person known to have mentioned Daylight Saving Time in 1784 when he wrote a letter to the editor of the Journal of Paris.

However, it was not widely used until more than a century later. William Willett, who was one of the first advocates for Daylight Saving Time in the U.K., published a pamphlet The Waste of Daylight in 1907, campaigning to advance clocks at the start of spring and summer months and to return to GMT in autumn.

Countries that follow DST

More than 140 countries have used it at some point, but about half of them have abolished it over the years. Arizona (except for the Navajo Nation), Hawaii, Puerto Rico, American Samoa, the Northern Marianas, and the U.S. Virgin Islands don’t recognise DST.

Though Europe, New Zealand, and a few regions of the Middle East follow the annual shift, each have different start and stop dates. However, majority of Africa and Asia do not change their clocks. South America and Australia are split on the matter.

Impact on health

For many people, the clock shift may result in missed meetings and sleep loss. However, this may also have severe health issues.

According to experts, with change in our internal clocks by even one hour, we develop “social jet lag”, which increases the risk of metabolic disorders, heart disease, and stroke, and shortens our sleep duration. Some studies have also suggested that time change can be linked to even fatal car accidents.

Picture Credit : Google 

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