I think Kim Stanley Robinson's R/G/B Mars series covered a workable Mars calendar in detail, FWIW.<p><a href="https://en.wikipedia.org/wiki/Mars_trilogy" rel="nofollow">https://en.wikipedia.org/wiki/Mars_trilogy</a><p>It's interesting that the recent SpaceX announcement of a Mars colonization plan included 100 colonists.
(OK, it was "at least" - perhaps it will be 101)
Except this time around we'll keep it simple, no time zones and expressed as YYYY solofyear.decimalofsol.<p>0010 372.5000 represents midsol of the 373rd sol of the 11th year since humans landed on Mars.