Marking the end of British Summer Time, the clocks go back in October, giving us an extra hour in bed

In autumn 2017 the clocks will go back on 29 October at 2am

On the last Sunday of October the clocks 'fall back': they go back by one hour. It may feel like a long time since the blue skies of summer, but this marks the end of British Summer Time (BST). This will mean an extra hour in bed. Clocks on smart phones should update themselves automatically, but older analogue clocks need changing manually. At the Royal Observatory, we even have sundials which need changing...


Why do the clocks go back?

The clocks go back to revert to Greenwich Mean Time (GMT) which was in place before British Summer Time started in March. The clocks went back for the summer because of a campaign at the beginning of the 20th Century to change the clocks during the summer months to avoid wasting time in the morning.

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 and reducing road accidents.

Aside from the obvious inconvenience of changing our clocks twice a year, opponents have presented different arguments against daylight saving, from safety concerns about darker mornings to farmers expressing concern about the effect of changing routines for their livestock. Others argue that the changing the clocks is now redundant, given that many of us now spend most of our time in well-lit homes, shops and offices where the amount of daylight makes little difference to our lives. Similarly, the economic and environmental advantages can vary; for some warmer regions, it’s thought that longer evenings may actuallyincrease energy consumption as people use air-conditioning units for more hours.

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

Greenwich Park and view over London in snow, with Queen's House and National Maritime Museum

Why do the clocks go back on the weekend?

This pattern of change was chosen because it occurs on a Saturday night/Sunday morning and 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.

An easy way to remember which way the clocks change is to think ‘Spring forward' and 'fall back'.

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 back.

Curator of the Royal Observatory, Louise Devoy, explains what happens here 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).

Image of the Dolphin dial at the Royal Observatory

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.

Find out more about the history of British Summer Time and daylight saving time in the UK and around the world

The Royal Observatory Greenwich, home of time

Stand on the historic Meridian Line and see the ground-breaking Harrison clocks.

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Harrison's marine timekeeper H4
Harrison's marine timekeeper H4