Terrestrial time refers to the time standard that is based on the rotation of the Earth around its axis. Some synonyms for terrestrial time include solar time, Earth time, and mean solar time. Solar time is based on the position of the sun in the sky, while Earth time refers to the time based on the rotation of the Earth. Mean solar time is the time that is based on the average position of the sun over a year. Other synonyms for terrestrial time include true solar time, apparent solar time, and standard time. Regardless of the term used, terrestrial time is important for timekeeping and synchronization of clocks around the world.