[LEAPSECS] POSIX and C (Was: Re: ISO Influence)

[Steve Allen]

On 2010 Dec 19, at 08:07, Poul-Henning Kamp wrote:

> Right, and you are advocating changing the POSIX standard, so ?


The POSIX standard is broken, admittedly broken, by insisting that
it conforms to something whose properties it cares not to implement.

In the absence of a uniform underlying time scale some systems
which really need uniformity choose to use the non-standard
shunned-by-the-BIPM GPS time scale.  They are choosing
practicality over conformance with international standards.

What POSIX wants is a uniform underlying time scale that has an
international recommendation standing behind it so that it is the
time scale which is available via the existing broadcast and network
distribution channels.  Systems which implement POSIX do not care
what name humans use for that international broadcast time scale.
Those systems and the code on them will work just fine if the name
of the time scale is changed along with the characteristics.

Of the code that cares to match with civil time of day, much assumes
that the same time next day is achieved by adding 86400 seconds to
a time_t.  Such code already fails by an hour when used across two
day boundaries every year.  The authority and wishes of POSIX do
not constrain the politicians from capriciously messing with the
civil clocks, we all just have to cope.

Code which makes use of zoneinfo to verify whether a daylight/summer
time boundary is being crossed gets the civil time right.  If the
leap seconds leave the broadcast time scale and go into zoneinfo
then those programs will continue to get the civil time right.
The other systems are already wrong and will not get notably more
wrong if they are following a time scale named TI instead of UTC.

Change the name of the broadcast time scale from UTC to TI (as
recommended at the 2003 Torino ITU-R colloquium), omit the leap
seconds from the broadcasts, and put them into zoneinfo.

The technology to do this is in place.  I expect that an inventory
of the systems adversely affected by this will indicate a smaller
effect than any of the other options. 
                                                        
--
Steve Allen               <sla at ucolick.org>              WGS-84 (GPS)
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