Dark at 9:03am in London – or why I like the clock change

Ok. Stand back. Let me explain. The hour shift only actually makes a difference for eight weeks a year.

What??? You all say.

Let me explain. Be careful now, this will involve science.

In the UK, the times of sunrise and sunset change by about 15 minutes a week or about an hour a month. So though we have a big jump this weekend when the clocks change, all that’s happened is that we’ve shifted Sunrise a month to when it was at the end of September, and shifted Sunset a month to when it would be at the end of November. There’s nothing in the clock change in October that we haven’t already had or wouldn’t have in a month’s time anyway.  It doesn’t make the daylight hours any shorter, though to listen to the grumpiness and ill-informed comments at this time of year, it seems that is what people think.

With me so far?

So the eight weeks which have sunset and sunrise times which we wouldn’t otherwise have are from Nov 22nd to Jan 22nd or so – ie a month either side of the winter solstice.

So here are the sunrise and sunset times and the length of the day for 21st Nov, 21st Dec and 21st Jan for London

Sunrise Sunset Daylight hours
07:29 16:03 08:34
08:03 15:53 07:49
07:53 16:30 08:37

Without the clocks changing, these numbers would be

Sunrise Sunset Daylight hours
08:29 17:03 08:34
09:03 16:53 07:49
08:53 17:30 08:37

I don’t know about you, but 9:03 is pretty late for sunrise and I hate actually going to work in the dark. So to my mind the clock change is worth it for those two months at least.

But guess what – even with the clocks changing, here in Edinburgh I do have to go to work in the dark.

Even though Edinburgh is only about half way up the UK, that is sufficiently further up the planet for those numbers to be inaccurate.  In January and November the daylight hours in Edinburgh are about 40 minutes shorter than daylight hours in London. and by December they’re about 50 minutes shorter. (Though of course, our daylight hours are longer by the same amount in midsummer).

So here are the sunrise and sunset times and the length of the daylight hours for 21st Nov, 21st Dec and 21st Jan for Edinburgh:

Sunrise Sunset Daylight hours
08:02 15:55 07:53
08:42 15:40 06:57
08:25 16:23 07:57

Without the clocks changing, these would be:

Sunrise Sunset Daylight hours
09:02 16:55 07:53
09:42 16:40 06:57
09:25 17:23 07:57

If it sucks when it’s dark at twenty to nine in the morning, it REALLY SUCKS if it’s still dark at twenty to ten! (I spent a couple of winters in Sweden – I know).

As I said, the specific eight week period between 22 Nov and 22 Jan are the only time when the sun rises at times it wouldn’t if we didn’t change the clocks.

I hope this helps explain

  1. why it’s not that much of a deal
  2. why you’d miss it in December if the clocks didn’t change and
  3. why I’d REALLY HATE YOU if they didn’t

3 responses to “Dark at 9:03am in London – or why I like the clock change

  1. And we don’t want to shift the other way and keep GMT all the year because in summer that means an absurdly early dawn – a waste of what used to be called God’s good daylight. To the extent that in the war years they had double summer time – which my mother said was rather difficult. Getting up at effectively 4am – albeit after sunrise and in daylight you really had now idea how the weather was going to turn out or what to dress for. Think how often a dawn is lovely fine and clear and then rapidly deteriorates.

  2. Most people sleep through dawn anyway. It would mean missing out on some of the lovely long summer evenings though.

    I’d be tempted to have the clocks change in November and back again in January so you only had the changes when they made a real difference.

    Or have them change in Scotland but not England and let people in London commute in the dark for a few winters.

  3. Sorry, the whole topic turns me into Mistress Temperful.

    We scoff at the people in the eighteenth century who rioted saying “give us back our eleven days” when the calendar was reformed. But people talk about the clocks changing in exactly the same way, as if it alters the hours of daylight.

    In midwinter there are less than eight hours of daylight in London and less than seven in Edinburgh – whenever time you set the clocks for, that’s just not enough to go round!

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