What is the total number of dark hours (after sunset) per year in the UK?
If you wanted to know the hours of light or darkness in a month, that would be a tough question. It would depend on your latitude and which month of the year it is. Summer has more light, winter has more darkness. But since you’re asking for the hours of light or darkness in a full year, that simplifies things nicely. The winter and summer months cancel each other out over a full year, so you can just say 50% of the hours are light and 50% of the hours are dark. There are 8760 hours in 365 days. 50% of that is 4380 hours.
Well I can give you a rough idea. Firstly, I got the data from my diary which gives sunrise and sunset times for various parts of England. Whilst not specifically stating that the times are from the Greenwich Meridian, it does give London as one of the examples and this is the one I used. Although it gives the variations on a week-to-week basis, I’m afraid I do have a life! So I checked the hours of darkness using the spring and summer equinoxes. This showed the hours of darkness as being 11 hours 54 minutes. To confirm the accuracy of this I found the hours of darkness for the summer and winter solstice and found the average of these to be 11 hours 46 minutes. I then decided to take the average of the averages which is of course 11 hours 50 minutes and multiplied it by 365. This gave me an answer of around 4319 hours. Hope that helps. I really must get out more!
