You can get 10ppm in a 32768 xtal.  The RTC specs I have seen indicate that
they are no more accurate than a PIC doing the same thing.  Dallas, for
example, claims +/- 30 sec/month (which is 10ppm).
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Bruce Cannon
Style Management Systems

Remember: electronics is changing your world...for good!

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> What kind of accuracy can one expect from a PIC with a X MHz crystal?
> If you assume that the crystal is off by 25ppm, you would be off by
> 0.000025 seconds per second.  This would mean gaining (or losing)
> 0.000025*3600*24=2.16 seconds in a 24 hour period.  This does not
> seem very accurate.
>
> >
> > [2] Use any PIC with a 32768Hz clock.  This will drop power consumption
>
> Is the 32768KHz crystals used for RTC's more accurate than the 'normal'
> crystals?  Or do you get the same kind of accuracy from them?
>
> Just wondering...
>
> Niki