cosmic time - the time covered by the physical formation and development of the universe. time - the continuum of experience in which events pass from the future through the present to the past. sidereal time - measured by the diurnal motion of stars. solstice - either of the two times of the year when the sun is at its greatest distance from the celestial equator. equinox - either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length.