This could be discussed:
819 days / 29.22 = 28 synodic cycles of the moon.
Indeed, dear MUU - and for those interested in the Maya astronomers’ knowledge of the remarkable cycles of Mars (which all by themselves disprove the Copernican / heliocentric model), this paper is a highly recommended read:
Ancient Maya documents concerning the movements of Mars
And here is the link to the section of my book which demonstrates how the TYCHOS model can readily - and most elegantly - account for the ‘mystery’ of the two different sidereal periods of Mars (of 707 and 546 days):