The clocks change on the last Sunday of March, moving forward by one hour. There may still be a chill in the air but this marks the beginning of British Summer Time (BST). 

In 2021 the clocks go forward on 28 March at 1am.

In 2020 they went forward on 29 March.

Will I lose or gain an hour in bed? 

Unfortunately, the spring forward means that we lose an hour in bed. An easy way to remember which way the clocks change is to think ‘Spring forward' and 'fall back'.

Why do the clocks change?

The clocks go forward for the summer because of a campaign at the beginning of the 20th Century to change the clocks during the summer months, in a practice known as British Summer Time.

The original campaign attempted to argue that by changing the clocks during the summer people in the northern hemisphere could make more use of the earlier daylight hours. 

William Willett - an early promoter of British Summer Time and great-great-grandfather of Coldplay singer Chris Martin - published a pamphlet in 1907 titled 'The Waste of Daylight', which suggested changing the clocks in the spring and putting them back in the autumn. However, Willett's proposal was complicated, involving advancing the clocks by 80 minutes. in four separate moves of 20 minutes each.

Willett died in 1915. A year later Parliament passed the Summer Time Act, which established the practice of putting the clocks an hour forward during the summer.

A family walks along the Prime Meridian Line at the Royal Observatory in Greenwich

Visit the home of time

Stand on the historic Meridian Line and see Harrison's ground-breaking time keepers at the Royal Observatory

What are the arguments for and against changing the clocks?

Today people argue that changing the clocks will be good for:

  • reducing energy consumption for environmental reasons
  • having longer evenings to support leisure and tourism
  • encouraging people to exercise more outdoors
  • reducing road accidents.

However, opponents of British Summer Time have presented different arguments against daylight saving time, from safety concerns about darker mornings to farmers expressing concern about the effect of changing routines for livestock.

Others argue that changing the clocks is now redundant given that many of us spend most of our time in well-lit homes, shops and offices, where the amount of daylight makes little difference to our lives.

It’s an ongoing debate that strongly depends on people’s geographical location, occupation and lifestyle.

Image
Stair trails on the horizon

'The Lost Hour'

Andrew Whyte's photo The Lost Hour was shortlisted for Insight Astronomy Photographer of the Year. He was inspired by the relationship between human methods of marking time (such as BST) and astronomical phenomena:

"I set out to explore what actually happens during that hour when the clocks "spring forward" to begin British Summer Time. With time so intrinsically linked to celestial activity, a one-hour star trail seemed the perfect metaphor.

"I worked out my placement and posture within the frame and could faintly hear the click of the first camera's shutter, which gave me a reference for freezing my movement.

"Back home, I merged 120 sky frames in StarStaX and layered that onto the RAW-processed foreground. As for the original question: what happens during the lost hour? The world keeps turning, just like before."

Why do the clocks change at the weekend?

The decision to change the clocks on a Saturday night/Sunday morning was made because it would be the least disruptive option for schools and businesses. To maximise the benefit of having extra daylight, it matches the warmest and longest days of the year.

Will my phone automatically update the time?

Most devices with internet connection, such as smart phones, should automatically update themselves. However, watches and clocks in cars and kitchens, for example, won't change automatically so make sure you are ready to wind forward.

Curator of the Royal Observatory, Louise Devoy, explains what happens in Greenwich when the clocks change:

Actually, I have very little work to do when the clocks change! We deliberately keep most of our historic clocks on GMT all year round as they were mainly used before the first daylight saving came into effect in 1916. Visitors arriving at the Observatory in the summer are often confused by the apparent delay shown on the Shepherd Gate Clock but as Britain’s first public clock to show GMT, we’re proud to continue this tradition.

The most significant change is our Dolphin sundial which needs to be adjusted four times a year: at the solstices (June and December) and when the clocks change (March and October).

Do other countries change the clocks?

About 70 countries have some form of daylight saving time, but it varies from region to region.

Much of Europe and North America, as well as parts of South America and Australasia, change their clocks. However, many countries in Africa and Asia situated around the equator do not change the time.

In the USA the clocks go forward on the second Sunday in March and back on the first Sunday in November, but not all states change their clocks.

Arizona does not use DST (apart from the semi-autonomous Navajo Nation), and neither does Hawaii. 

United States clocks change 2021

  • Clocks go forward on 14 March 2021
  • Clocks go back on 7 November 2021

In March 2019, the European Parliament backed a proposal to end the practice of changing the clocks in European Union states. If the proposal is adopted, EU nations could change the clocks for the last time in 2021.

History of daylight saving

1784 - Benjamin Franklin first suggested the idea of daylight saving time in a whimsical article.

1907 - An Englishman and keen horse rider, William Willett campaigned to advance clocks in spring and summer and return them in the autumn. His rather complicated plan was to advance clocks by 80 minutes, in 4 separate moves of 20 mins each.

1908 - The House of Commons rejected a Bill to advance the clocks by one hour during the spring and summer months.

1916 - The Summer Time Act was passed, ordaining that for a certain period during the year legal time should be one hour in advance of GMT. Double summer time (GMT + 2 hours) was used during the Second World War.