Re: why time zones
It must go back to when 12 o'clock was decided to be the moment when the sun was highest in the sky, during the day.
That custom was taken to where those who adopted it, emigrated.
And because they went very far, the sun wasn't at the same place at the same moment.
But the custom stuck (another one is the use in our languages of "sun setting" or "sun rising").
Raoul