On previous experience, crystals do not give a good time base for a
clock as the frequency varies quite a bit with temperature. I can get
+/- five or ten minute error over 1 day. The mains is reasonably
accurate for this purpose. ( Most commercial clocks rely on this fact.)

I would like to know if this is the best method for long term
accuracy or if there is a better way. (Albeit cheap).

Tony


Just when I thought I knew it all,
I learned that I didn't.