Spain moved to Central European time to facilitate coordination with Germany during WWII. I believe it was in 1940. It is an hour later than what it was previously. When I say that clock time is arbitrary, I mean just that. There is nothing natural about sunrise being at 6:00, 7:00 or 8:00--it's just what we have agreed on. We could just have easily agreed that sunrise would be at 15:00, and if we had, that would seem "natural."
You are correct that the rest of the post had nothing to do with yours, but rather was connected with the original post. I live in Spain (and since I'm retired, I do take siestas), and I find it annoying that two separate issues--Spain's geographically inappropriate timezone, and Spain's inconvenient commercial hours--tend to be conflated. It's the siesta schedule that truly affects people, not the odd timezone.