[tz] [PROPOSED] Sub-second history for Maputo and Zurich

[Steve Allen]

On Fri 2024-05-24T15:33:23-0700 Paul Eggert via tz hath writ:
> * africa (Africa/Maputo), europe (Europe/Zurich): Add #STDOFF
> comments for two zones with well-sourced standard time that was
> not an integral number of seconds away from UT.  This does not
> change the TZif output files.

I urge great caution for the use of subsecond offsets.

In 1853 some observatories were still calculating their time using
tables of the motion of earth which were based on recent observations
of the sun, whereas other observatories had begun to use tables of the
motion of earth based on perturbation theory where the mean sun was
calculated over an interval of millennia where the resonance
3*Jupiter - 8*Mars + 4*Earth (with a period of about 1850 years)
moved the mean mean sun 0.5 time second away from tables based on
recent observations of the sun.

As late as the 1920s the tabulations of received time signals in BIH
Bulletin Horaire show that different radio broadcasts of Universal
Time differed from each other by 0.2 time second or more.

Even as late as 1958 the USNO radio broadcasts differed from the BIH
value of UT2 by 0.03 time second because the values USNO used for its
longitudes and the values BIH used for longitudes were not expressed
in a globally consistent reference frame.

--
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
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