Daylight Saving Time

I've never spent a lot of time thinking about daylight saving time. It's a thing that annoys me once a year and makes me happy once a year. I never gave it much more thought than that, other than to kind of vaguely think that it seemed pretty stupid, and having the impression that this was a commonly held belief.

A few weeks ago, I read Craig's weeknotes, where he wrote:

My social feeds have been full of people grumbling about daylight savings, and that’s set to kick off again next week when UK clocks change. But I love it. (The clocks changing – not the grumbling.) In an instant, we’ll go from sunset around 18:30 to 19:30, meaning I’ll be able to start playing football in the street with my daughter after dinner again."

This actually got me wondering what the real impact of daylight saving time was. A quick search led me to, a super cool website that provides a free API that returns sunset and sunrise times for any location on earth. So I wrote some code to visualize the effect of daylight saving time at my location.

Here it is:

Graphical illustration of the length of each day across a year's time

From top to bottom, this shows the daylight for each day. You can clearly see when daylight saving time becomes active, and when we switch back to standard time. The blue areas on either side are the times when I'm typically asleep.

At least in my location for my sleep pattern, daylight saving time makes sense. I gain some light in the evening without losing any in the morning.

However, standard time doesn't seem to make a lot of sense. It would be more sensible for daylight saving time to be used for the whole year. I now lose some morning light because I sleep through it. By keeping daylight saving time all year, I would get that lost light back in the evenings. The only cost would be very dark mornings around the winter solstice.

If you want to see a graph like this for your location and your sleep pattern, go to and see for yourself.1 You need to give the page access to your location for it to work. If you get an error, try again in a few minutes. And if you find this useful, buy the guy who made the API a coffee.

  1. Note that if you're publishing generated pictures, you're probably doxing your own location, since the light pattern narrows down possible locations you could live at. ↩︎

If you require a short url to link to this article, please use

designed for use cover

But wait, there's more!

Want to read more like this? Buy my book's second edition! Designed for Use: Create Usable Interfaces for Applications and the Web is now available DRM-free directly from The Pragmatic Programmers. Or you can get it on Amazon, where it's also available in Chinese and Japanese.