Such an orbit relative to the stars is called a sidereal year.
The exact length has been variously defined either that of a solar day or of a sidereal day.
The satellite traces the same analemma once each sidereal day.
By convention, rotation periods of planets are given in sidereal terms unless otherwise specified.
A mean solar day is, therefore, nearly 4 minutes longer than a sidereal day.
Although there are 28 days to a sidereal month, by custom only 27 days are used, the last 28th day being considered unlucky.
The true position of these stars is only approximate to their theoretical equidistant rhumbs on the sidereal compass.
It is 27.32158 days, very slightly shorter than the sidereal month (27.32166) days, because of precession of the equinoxes.
