[tz] The zoneinfo file system tree structure ?

Steve Allen sla at ucolick.org
Fri Feb 13 19:54:05 UTC 2015

On Thu 2015-02-12T16:56:55 -0500, J William Piggott hath writ:
>        There  are  two  separate  databases  in the zoneinfo system, posix and
>        'right'. 'Right' (now named leaps) includes leap seconds and posix does
>        not.

>              To  use  the  'right'  database  the System Clock must be kept in
>        UTC + leap_seconds, i.e., TAI - 10.

I would clarify that to read

		To use the 'right' database the System Clock must
	  count allseconds of UTC (and TAI), including leap seconds.
	  From the beginning of 1972 onward this is equivalent to
	  setting the System Clock to (TAI - 10 s).

>                                             This allows calculating  the  exact
>        number of seconds between two dates that cross a leap second epoch.

I would clarify that to read

					      This means that the difference
	between two dates that span a leap second counts the number of
	seconds of TAI (and this is not congruent with POSIX).

>                                                                            The
>        System Clock is then converted to the  correct  civil  time,  including
>        UTC,  by  using the 'right' timezone files which subtract the leap sec-
>        onds. Note: this configuration is considered experimental and is  known
>        to have issues.

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