A few years ago I went to Spain for the first time, and like many I was surprised by how late is dinner. The first night I dined almost alone in a restaurant at 8pm, going away just as people were starting to come in. [N]ear the winter solstice, Madrid’s sunset is around 17:55, more than an hour later than the sunset in, for example, Naples, which is at a similar latitude.
Looking for other regions of the world having the same peculiarity of Spain, I edited a world map from Wikipedia to show the difference between solar and standard time. It turns out, there are many places where the sun rises and sets late in the day, like in Spain, but not a lot where it is very early (highlighted in red and green in the map, respectively).
So why is this?
Part of the reason is simply that days don’t actually have the same length. The modern calendar simply tolerates this with true midday not actually being noon, and letting it go at that. Different regions are also at different longitude, and that also impacts it, making the entire concept of “time zone” kind of a culturally agreed upon fiction.
Political considerations can also enter into this; a big part of the reason Spain is as displaced in its time zone as it is is in order to allow it to be at the same time as central Europe. Similarly – and resulting in an even more severe extreme – the entirety of China is locked the coast’s solar time resulting in a difference of what would otherwise be three hours.
Google engineer and math blogger Stefano Maggiolo on his The poor man’s math blog.