A kid should be able to put a stick in the ground, look at a
shadow, visually compare it to a wall (most of which are build
north/south/east/west side anyway) and know that its time to
come home for supper.
This amazing map shows what's wrong with Time right now. It
shows how far off the real time (solar time) is from our
fictional Time (time zones and stuff)
As far as the numbers that are used for certain times, I don't
see why there couldn't be the same time all over the world -
same numbers referring to the same time all over the world. We
already do that with computers - they just count 'up' from a
particular starting date and have to translate into 'our' weird
time zones.
But Why should it matter if 10pm is suppertime in Finland and
10pm is breakfast in Brazil? Ok, songs like ''It's five o'clock
somewhere'' might lose their meaning over time.
I wouldn't want to impose one system on the world like that
though.
Of course places would be free to say ''No, we want our five
o'clock to mean something special here'' and they would choose
to keep their own local time. They already do that now.