From early sunsets to the long stretch

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Photograph taken at 15.59 on Friday 10 December 2021, two days before the earliest sunset time.

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Photograph taken at 16.02 on Tuesday 14 December 2021, one day after the earliest sunset time.

This is the time of the year when the earth’s orbit round the sun as seen in the northern hemisphere moves past the point where we have the least amount of daylight. In Dublin this year the earliest sunset was at 16.06.20 on both 12 and 13 December and the latest sunrise was at 08.40.17 on 29 December. The dates and times straddle the actual solstice which was on 21 December and is the day on which the shortest total daytime occurs. This year the daytime clocked in at 7h 30m 6s. (The reason why these dates vary was explained in this post of mine in 2016.) I have previously relied on the website but this only provides the data in hours and minutes. The site grills down to seconds in its listings, although the exact times differ slightly from the figures. Here is a screenshot from its site:

Dec sunrise-sunset

Because we have had a few lovely bright afternoons this month I have managed to take some good photographs in the Phoenix Park near the time when the sun dips below the horizon, as seen while walking my dog Evie. The pics taken on 10 and 14 December are shown at the top of this post.

These pictures were all taken on bright afternoons, but when returning to my car on a different dull and misty day I was approached by a man with two large professional-type cameras slung round his neck. He turned out to be none other than Alan Betson, the celebrated Irish Times photographer. He had taken some pictures of Evie and me, and was about to send them in to the picture desk as possible shots for the next day’s gallery feature. Duly flattered, I of course agreed, and gave him our names.

Charles Foster and his dog Evie enjoy a walk in Dublins Phoenix Park

A dull day in the Phoenix Park. Pic: Alan Betson/Irish Times.

Sadly for me, the picture lost out to a much more joyful shot of a grandfather and grandchildren walking nearby. Our mundane trudge may not have been recorded in the national press, but with Alan’s permission, you can enjoy it as seen above.


Sunset and the Equation of Time


Phoenix Park, Dublin. Photograph taken at 1604 on 29 November 2016.

Around this time of the year, I get quite obsessed with the time at which it finally gets too dark to walk my dog. Like many other Dublin dog-owners, I go to the Phoenix Park (a few minutes drive from my house) for her afternoon excursion. It has acres of space in which to walk and often several other dogs with whom mine can run around, so there is much to commend it.
But in order to complete our walk in twilight, we have to start walking about 30 minutes before sunset, which is why timing is crucial. For several years, I have used the wonderful Time and Date website to check when sunset occurs. Amongst the hundreds of useful (and free!) pages included on the site (world telephone dialling codes, for example) is a nifty sunrise/sunset calendar for any location on the planet. I have used this to compile the table below for sunrise and sunset times in Dublin from 15 November 2016 to 7 January 2017:

Sunrise sunset.pages

The most noticeable things in this table are the times I have highlighted in red: the earliest sunset times actually occur between 10 and 15 December, more than a week before the Winter Solstice on 21 December. The 21st may well be the shortest day of the year, but by then sunset has already advanced by two minutes, and the latest sunrise will actually occur eight or nine days later on 29/30 December.
So why does this occur? As you would expect, has the answer: it is apparently because of a phenomenon called The Equation of Time as well as a location’s latitude. At the time of both the Winter and Summer Solstices, the length of a solar day (as measured by a sundial) is longer than 24 hours (as measured by a clock).
This explains the discrepancy, and has a pleasant consequence for us dog walkers. By Twelfth Night on 6 January, the sunset time has already advanced by 18 minutes over the earliest time. As they say over here in Ireland, we will be beginning to notice the stretch in the evenings by then.