Civil time is another name for mean solar time reckoned from midnight. Some astronomical and navigational timekeeping conventions in use before the mid-20th century reckoned the beginning of the mean solar day at noon. At one time Greenwich mean time (GMT) could refer to either convention, so the International Astronomical Union introduced the term Universal Time to suggest GMT with the civil day beginning at midnight.
Civil time has precise astronomical meaning. However, more recently this term is sometimes found with reference to specific statutory or standard time scales designated by civilian authorities, or with reference to local or standard time indicated by clocks. Generally speaking, the non-astronomical uses of this label are considered imprecise.