Message to `tz' mailing list

[Olson, Arthur David (NIH/NCI) [E]]

> I am confused about the use of the UTC/local indicators and the
standard/wall indicators in a tzfile.  According to tzfile(5), they "are
used when
> a time zone file is used in handling POSIX-style time zone environment
variables".  Does this mean that these indicators are irrelevant when
computing
> local time using only a tzfile (without looking at the environment).

That's correct: the ttisgmt and ttisstd indicators can be ignored if
you're simply trying to figure out what wall clock time is for the zone
that's associated with the file.

(The indicators are there for the case when the time zone file is used
as a "template" for the DST rules to be used when handling POSIX-style
TZ environment variables; you need to know whether the transition time
is defined in terms of UTC, local wall clock time, or local standard
time to be able to know when translating the transition time for use in
another zone.)

				--ado