[LEAPSECS] POSIX Time

[Joe Gwinn]

At 9:49 AM -0700 10/10/09, Steve Allen wrote:

>POSIX time is simply self-inconsistent as defined.

>Different commentators with different preferences cue on different

>aspects of the inconsistency.


POSIX Time as defined is self-consistent, but for various mostly good 
reasons isn't what many people want, and there were protracted time 
wars in the POSIX committee about what POSIX Time should and should 
not be.  There were many partisans, each loudly and intolerantly 
proclaiming that only they possessed the One True Clock, while 
ignoring the problems that any POSIX timescale must solve to be 
accepted.

The partisan fighting soon exhausted the Committee, who then threw 
their hands up and mostly stuck with a slight cleanup of the prior 
standard wording.



>I prefer to point out that no interpretation of POSIX time can

>be consistent with the legal time standard of all nations which

>was in contemporary use, as in the javascript here

>http://www.ucolick.org/~sla/leapsecs/epochtime.html


I can well believe this.  POSIX Time as used is neither TAI nor UTC. 
In practice, this inconsistency matters little -- most people just 
use NTP-distributed UTC from GPS receivers and get on with life.



>As such I do not expect that international standards bodies

>will ever be able to produce anything other than a compromise

>interpretation.


The POSIX Committee threw the partisans out for a simple reason - the 
partisans were screaming at each other and at the committee members 
in timetalk, an obscure foreign language, and very few in the 
Committee could even follow the arguments, let alone decide who to 
agree with.  Most committee members are experts in UNIX/Linux 
operating system internals, know little to nothing of time, and have 
little motivation to become experts in time.  And they had bigger 
fish to fry.  So the Committee was forced to punt.

If the timefolk were to have their fights and bury their dead in 
private, and only then have the survivors present a unified proposal 
to the Committee, it might be possible to get the definition of POSIX 
Time updated.  The next opportunity to change is in about three 
years, when the development of the next revision of the POSIX 
standard will be undertaken.

Joe Gwinn

Vice Chairman, POSIX
Chairman, POSIX Realtime Subcommittee



>--

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

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