I don't really think it makes sense to ask about 'the speed of time'.
What we mean by speed is how much of something happens per time
increment. Whatever units you choose to measure time in (seconds,
years, etc) it takes just one of those units for one of those units to
The only speeds that have meaning are the comparisons of two
different rates- say how many periods of the light coming from a He-Ne
laser occur during one heartbeat, etc. Much of phyics, chemistry, and
biology are devoted to figuring out such comparative speeds, so there's
no one simple formula to cover the whole lot.
Your other question is about isolating a single point in time. In
general,there are different ways of taking slices through all the
events in space-time to get different collections that you say are
'simultaneous'. None of these slices are any more or less true. So
there are problems trying to define a single point in time, unless you
also mean at a single point in space. There are other problems with
that too, but probably that's enough nay-saying for now.
(republished on 07/23/06)