Re: The meridian is, by definition, when the sun is directly overhead.
I'll try to remember that next time I'm standing exactly on the Greenwich Meridian in winter.
am and pm have lost their very specific meaning and now are understood as "in the early hours of the morning or the morning" and "in the afternoon, evening, night-time, I wonder if I should go to bed yet? Do you remember when the screen used to go to a white dot and whistle at you?"
It still doesn't help in the 12am/12pm issue. We don't have a 0am... what would that mean?