Ralph Mowery wrote:


Can't say about the UK but in the US the clocks that run only on the power
grid and depend on the frequency are very accurate over a long period of
time. I would say more like less than a minuit or less over a year period
of time if the clock its self is up to it. During periods of peak loads the
nominal 60 hz may go down a cycle or so and when the load is taken away the
power company will raise the frequency long enough to get the clocks back in
time.

I read an article a few years ago that discussed how the frequency is
regulated in the US. I can't find it now. I think it was by David
Mills
from the University of Delaware. As I reacall, there are 2 power grids
in the US. The Eastern grid is controlled by an automated system
at some power plant in Ohio. The Western grid is controlled manually.
I wish I could find the article, it had some interesting stuff.

Things are probably done in a similar fashion in the UK.

- Mooron