Telling the time in Alexanderplatz

I've been back in Berlin on another fantastic trip. I noticed some new things this year, like this clock in Alexanderplatz. Sadly, I only got a good look at it on the last night. I think that the numbers in the middle rotate. It was almost 9pm in Berlin so I suspect the bottom picture shows it about to flick round. But it was a useful way of explaining the way that 12noon is only a number given to the time when the Sun is highest in the sky where you are. We were further east than London so that happened an hour or so earlier. Rather than have each place have its own perfect adjustment (eg Wigton is really about 10 minutes behind London) we divide the world into 24 strips and within that strip they are all supposed to have the same time. An approximation to the Physics but more practical.