Does the time change from GMT to GMT+1 affect readings on a sundial?
I thought that it probably wouldn’t affect it all that much, as sundials are not all that accurate, generally speaking. I also thought that the Earth would be in a different position (in relation to the Sun) in Winter, than in the Summer months. I did google it, and was pleased to find that my answer was not too far off the mark - GMT is based on the time on the meridian line only (which happens to run through Greenwich, hence “Greenwich Mean Time”, meridian being equivalent to mean). But to simplify this, the surrounding areas are also put into the same time zone. An example would be Sheffield – it is 1.5 degrees off the meridian line, and so as a result, at the peaks of each season (21st June and 21st December), a sundial in Sheffield would show as up to 15 minutes out, against the “true” time. Twinned with the vagueness and simple design of a sundial (it has an hour hand only, no minute hand), this means that although we alter our clocks twice a year, sundials are not affected enough by this to render them defunct or inaccurate.