Sidereal Day

One Sidereal Day is  23.9344699 hours or 86164.09 seconds

The Math / Science

The sidereal day accounts for the fact that the Earth is traveling around the Sun in addition to rotating on its axis.  The Earth rotates in 86,400 seconds (24 hr X 60 min/hr * 60 s/min) and the solar day is 1/365 time longer than this because in one day the Earth traverses 1/365 of the Earth's orbit around the Sun.