Coordinated Universal Time (UTC )

time scale [...] with the same rate as International Atomic Time (TAI), but differing from TAI only by an integral number of seconds [...] Note 1 to entry: UTC is the time standard commonly used across the world from which local time is derived. Note 2 to entry: UTC is produced by the Bureau International des Poids et Mesures (BIPM), i.e. the International Bureau of Weights and Measures. Note 3 to entry: TAI is a continuous time scale produced by the BIPM based on the best realizations of the SI second. TAI is a realization of Terrestrial Time (TT) with the same rate as that of TT, as defined by the International Astronomical Union Resolution B1.9 (2000). [SOURCE:BIPM Recommendation CCTF 3 (2017), modified — The definition of TAI has been included as Note 3 to entry.]