[time-nuts] keeping Arduino timekeeping and clock synced up

[Mark Sims]

The EOT code that I linked to (http://www.astronomycorner.net/games/analemma.c)  and am using is interesting because it appears to be applicable to other planets.  It has parameters like the orbit obliquity/eccentricity/perihelion/year length that can be changed.  It also does not make assumptions like the time of perihelion is 12 days past a fixed value of the winter equinox (i.e. Jan 2).
A clock routine that I wrote for the ATMEGA2561/ATMEGA128 runs off of a 10Khz interrupt.  It does a first-order compensation for crystal drift by occasionally ignoring or duplicating timer tick processing.  It can produce very good long-lerm clock performance.   
I also have had very good results using the DS3231 temperature compensated clock chip.  My alarm clock uses a Trimble Res-T GPS backed up by the DS3231...
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I've got the Arduino code running that does the EOT