[LEAPSECS] Common Calendar Time (CCT) - timescale design -Brooks Harris

[Steve Allen]

On Sun 2014-01-19T23:53:44 +0000, Zefram hath writ:

> I'm not familiar with PTP, but I see a number of documents saying that it

> uses an epoch of 1970-01-01 00:00:00 TAI.  If so, unlike the NTP origin

> this is a perfectly well-defined real instant.


Yes, well-defined, but not defined in a contemporary sense that any
such time stamps could have existed.  Anything with that stamp
was reconstructed ex post facto.

The CCDS meeting which produced the definition for TAI was held
1970-06-18/19.  After that got to the CIPM that became known as
Recommendation S 2 (CCDS, 1970), in CIPM, 1970

The CGPM meeting which authorized the existence of TAI was
opened 1971-10-04 in Resolutions 1 and 2.

This is a perennial problem in metrology of things that progress.  If
a precise definition is desired for a coordinate origin then that
origin must be expressed in measures of the current conventional value
with current technologies.

The past of POSIX time stamps can never be disambiguated without
argument.  If it becomes possible to choose a new time scale with
which everyone can live then the POSIX standard will have to specify a
new conventional date at which time_t has a new conventional count of
seconds.

--
Steve Allen                 <sla at ucolick.org>                WGS-84 (GPS)
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