Word origin · etymology
Standardized alphanumeric name.
UT abbreviates Universal Time; the 1 distinguishes the version corrected for polar motion from historical UT0.
How we know · epistemology
Observed Earth rotation
UT1 is determined from Earth-orientation measurements and models. Earth does not rotate perfectly uniformly, so using civil UTC as an exact substitute can affect precise horizon calculations.
Connected concepts
Terms used in this explanation
Mentioned in 6 other entries
These links connect subjects and terminology. They do not establish a shared historical origin.
Sources & provenance
Use the citations beside each section to distinguish a calculation convention, a historical teaching and an editorial example.