UT1 vs GMT

UT1 and GMT both are nouns.

Word	Noun	Adjective	Verb	Adverb
UT1	Yes	No	No	No
GMT	Yes	No	No	No

As nouns, UT1 and GMT are synonyms defined as:

UT1 and GMT: the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere

Other synonyms of UT1 include Greenwich Mean Time, Greenwich Time, universal time, UT.

UT1 (noun)	GMT (noun)
the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere	the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere