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International Earth Rotation and Reference Systems Service
Glossary
The following terms are related to the IERS and to Earth rotation and reference systems in general.
Additions will follow, proposals are welcome.
Universal Time (UT1)
Acronym: UT1 In French: Temps universel
UT1 is the rotation angle about the Earth pole.
UT1 can be regarded as a time determined by the rotation of the Earth. It is distributed by the IERS as the difference UT1-UTC in IERS Bulletins A and B and in other data files.
Universal Time (UT) is counted from 0 hours at midnight. The unit of duration is the mean solar day.
UT0 is the rotational time of a particular place of observation.
UT1 is computed by correcting UT0 for the effect of polar motion on the longitude of the observing site.
