SIDEREAL TIME

The measure of time as defined by the diurnal motion of the vernal equinox. A sidereal day is equivalent to one complete rotation of the earth relative to the equinox, which is 23 hours, 56 minutes, and 4.091 seconds. A sidereal year is the interval required for the earth to make one absolute revolution around the sun, which is 365 days, 6 hours, 9 minutes, and 9.5 seconds. Compare with the solar day.