[LEAPSECS] Time math libraries, UTC to TAI

[Steve Allen]

On Sun 2016-12-25T19:37:31 -0700, Warner Losh hath writ:
> I think that POSIX has de-facto redefined UTC, and it's time that the
> UTC standard catch up to this quiet revolution.

POSIX has defined that the time scale upon which time_t is based has
the characteristics of every time scale other than UTC.  That is,
there are 86400 "seconds" in a "day".  That will stay true until
POSIX is in use for civil time somewhere else than on earth.

It is less clear is what kind of "seconds" and "days" POSIX wants,
largely because the current UTC did not make the distinction clear.
Thus for POSIX the "seconds" being ticked and "days" of the calendar
must be related by the factor 86400, which is not the case in UTC as
defined by CCIR/ITU-R.

It is clear that devices implementing POSIX must rely on the time
signals in radio broadcasts.  Too much infrastructure already exists
which relies on those broadcasts.

It is clear that the agencies implementing the radio broadcasts will
never return to rubber seconds, and will not approve of smears.

So the only change that can happen to the nature of radio broadcasts
is to start counting atomic days of atomic seconds.

It is not clear that the name UTC is sacrosanct to POSIX.
The machines simply do not care what humans call that time scale.

It is clear that some humans do care about the name UTC.  I have not
seen any of the agencies make arguments about why the radio broadcast
time scale cannot change its name.  It has done so in the past, and
the world did not care.

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