sidereal-day

The Earth SOLAR Day = 24 hours. In tables of Solar System numerical data, the orbital and rotation periods are pretty much always expressed in Earth Solar days. An Earth SOLAR Day is the time period between successive risings of The Sun on a fixed horizon upon Earth.

The Earth SIDEREAL Day = 0.9972697 Earth SOLAR Days.

An Earth SIDEREAL Day is the time period between successive risings of any specific STAR on a fixed horizon upon Earth. (The word “sidereal” means pertaining to a star.) It is slightly less than The Earth SOLAR Day because The Earth is revolving round The Sun.