Coordinated Universal Time (FTC Temps Universel Coordonné; UTC) is the standard by which society regulates hours and time. It differs by an integer number of seconds from atomic time and by a fractional number of seconds from universal time UT1.
The abbreviation UTC does not have a specific decoding. When in 1970 it was required to create a language-independent abbreviation, the International Telecommunication Union considered that the English CUT = Coordinated Universal Time or the French TUC = Temps Universel Coordonné were not suitable for this role. Therefore, a neutral version of UTC was proposed.
UTC was introduced instead of the obsolete Greenwich Mean Time (GMT). A new UTC timeline has been introduced since the GMT scale is an uneven scale and is related to the Earth’s daily rotation. The UTC scale is based on a uniform atomic time scale (TAI) and is more convenient for civilian use.
Since the difference between UTC and UT1 does not exceed 0.9 s, if high accuracy is not required, the more general concept of Universal Time (UT) can be used. In everyday life, when the fractional part of a second is not important, Greenwich Mean Time (GMT) can be considered the equivalent of UTC or UT1. Otherwise, when the difference between UTC and UT1 is significant, the use of the term Greenwich Mean Time (GMT) is avoided.
Time zones around the globe are expressed as positive and negative offsets from UTC.
It should be remembered that UTC time is not translated either in winter or in summer. Therefore, for those places where there is a switch to daylight saving time, the offset relative to UTC changes.