When do the clocks go back?
The clocks go back today, the last Sunday in October.
25th October is the earliest possible date the clocks can go back, ushering in darker evenings at the earliest opportunity.
When did the clocks go back?
before 1916: they didn't
1916-1924: various dates in late Sept/early Oct
1925-1938: the day after the first Saturday in October
1939-1947: it's complicated (thanks to Double Summer Time)
1948-1949: the day after the last Saturday in October
1950-1952: the day after the third Saturday in October
1953-1960: the day after the first Saturday in October
1961-1967: the day after the third Saturday in October
1968-1970: they didn't (thanks to permanent Summer Time)
1971-today: the last Sunday in October
» For a full history of British Summer Time dates see my 2025 clocksback blogpost
When do the clocks go back?
At 2am BST, reverting to 1am GMT.
It's been 2am ever since 1916.
2am on Sunday was chosen because it was the quietest time of the week, after trains had stopped running but before shift workers and churchgoers set out.
This means there are two half-past ones, indeed an entire hour repeats.
It means you could have two twins, the elder born at 1.55 and the younger at 1.05.
It also means October is the longest month of the year, one hour longer than January, May, July, August and December (and two hours longer than March).
» For much more about British Summer Time see Wikipedia
Why do the clocks go back?
Essentially it's to provide more daylight in the evenings from April to October.
The initial trigger in 1916 was to support the war effort by increasing daylight during the working day and reducing energy consumption for lighting.
In the UK the man with the original idea was Chislehurst builder William Willett.
» For more on William Willett see my 2007 clocksback blogposts (also my 2015 clocksforward blogpost)
» For more on daylight changes see my 2021 clocksback blogpost
How long do the clocks go back?
There are always either 21 or 22 weeks of Greenwich Mean Time before the clocks go forward again.
This year it's 22, sorry.
There are 22 weeks of GMT most of the time (17 years out of every 28, i.e. 61% of the time)
It's 21 next year, hurrah.
» For the longest periods of British Summer Time see my 2022 clocksback blogpost
Why do the clocks go back asymmetrically?
Clocks go back two months before the winter solstice but go forward three months afterwards.
This means they go back when sunset is around 5pm GMT, but don't go forward until sunset is around 6pm GMT. This is neither balanced nor ideal.
If things were better balanced we'd put our clocks forward at the end of February rather than the end of March.
This would avoid a slew of March evenings that are darker than they need to be.
I understand the reason for the imbalance is that October evenings are mild (so it's still worth going out), whereas March evenings are cool (so there's less incentive to head outdoors), but I suspect farming comes into it somewhere too.
» For more asymmetry see my 2011 February Forward blogpost
Where do the clocks go back?
They go back today all across the UK, the Isle of Man and the Channel Islands.
Also across the EU (including Ireland and Portugal, whose Summer Time is the same as ours).
Also in many other European countries (including Norway, Switzerland, Ukraine, the Balkans and the Baltics).
Also Israel and Lebanon (Palestine switched last night and Egypt jumps back on Thursday).
Meanwhile the USA, the eastern half of Canada and most of the Caribbean go back next weekend.
Their clocks always go back one week after us (whereas their clocks go forward two or three weeks before us).
» For more national detail see Wikipedia on Daylight saving time by country
Where don't the clocks go back?
All of Asia (except Israel, Palestine and Lebanon).
All of Africa (except Egypt).
Equatorial countries (because Daylight Saving isn't useful where sunset times don't vary much).
Also the whole of the southern hemisphere (except New Zealand, southeast Australia and northern Chile).
What happens when the clocks go back?
Essentially the time of sunset suddenly jumps an hour earlier. People hate that.
It's only been a week since the last day London had a sunset after 6pm.
Now suddenly sunset is before 5pm, and it all feels terribly premature.
But make the most of tonight's 4.45pm sunset.
It may feel miserable but it'll be 31st January before we get a sunset later than that.
Sunrises work completely differently.
This morning's sunrise is at 6.40am, which we last had on 19th September.
We next get a 6.40am sunrise on March 3rd, and then again on March 30th.
This all feels counterintuitive, but we pay far less attention to sunrise than sunset.
» For more on sunrise/sunset changes see my 2021 equinox post
Why don't we modify when the clocks go back?
So much debate, so many arguments.
Daylight saving has always been controversial ever since it started.
Why should we do it, why don't we stop doing it, why don't we delay it, why don't we do it twice?
There have been numerous parliamentary debates about altering it, also EU directives suggesting it ceases, also drives to introduce Double Summertime instead, all backed up by arguments that work for some people and not for others.
Here's a comments box especially for people who want to discuss changing our daylight saving rules. I'll delete it later. comments
» For shallow BST commentary see my 2002 clocksback blogpost
» For more on Double Summertime see my 2011 DST blogpost
» For more on the EU termination proposal see my 2019 EU blogpost
Whither do the clocks go back?
They went back an hour at 2am, which was simultaneously 1am, and won't go forward again for 154 days. Get used to it.
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