> This sounds way to simple to be of use, but....
> Just have the first minute after every even hour (except midnight)
> consist of 59 seconds

(the xtal is running fast BTW, so make that 61s)

Bill, a bit kludgy (it has a display and imagine the puzzled looks when
a time holds for 2s), but would work. It does involve knowing what the
error for every unit is however. I'm kind of leaning towards "teaching
by example". Show the micro what a real hour or day looks like and
then getting it to work out how to do it itself. What that would do is
actually similar to what you're thinking of, except it does it at the IRQ
level, by figuring out a combination of 0.01s and (0.01+a tad)s to make
the TOD run a tiny bit slower on average than it otherwise would have

Ideally I'd want to use something like Maxim's new TXCO

http://www.maxim-ic.com/view_press_release.cfm?release_id=654

but <oooh, sucks air through teeth> NZ$30, BGA package and
even at 1ppm that's still 30s per year

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