[tz] What's "right"?

Steve Allen sla at ucolick.org
Thu Nov 12 19:50:12 UTC 2020

On Thu 2020-11-12T12:11:52-0700 Paul Gilmartin via tz hath writ:
> Was UTC defined in 1970, or should it pedantically be GMT for 1970
> and 1971; TAI-10 thereafter?

Pedantically there are no answers which are universally true.

During 1970 and 1971 (and a few years before) different time service
bureaus were providing various different time scales with various
different names in their radio broadcast time signals.  US NBS
provided two different broadcasts with different time scales (old UTC
and stepped atomic time SAT).  German PTB provided two different time
scales at different times of day using the same transmitter (old UTC
until that became illegal in Germany, thereafter SAT).  During those
years the terminology UTC was only known inside the time service
service bureaus.

As for GMT, the final observation using the Greenwich meridian circle
was 1954-03-30.  After that date there was no authority who could
provide a definition of GMT.  The last use of that term by almanacs
was in 1959.  The term GMT continued to be used by some time service
bureaus, but in accord with CCIR recommendation 374 they were
broadcasting the original form of what was internally known as UTC.

On 1974-01-01 NBS WWV stations started announcing as UTC.  In 1976 the
IAU urged no further use of GMT.  In 1978 the CCIR was informed that
GMT was no longer used.  In 1980 the CCITT specified UTC to replace
GMT for all telecommunications activities.

Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
1156 High Street               Voice: +1 831 459 3046         Lng -122.06015
Santa Cruz, CA 95064           https://www.ucolick.org/~sla/  Hgt +250 m

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