[Octave-bug-tracker] [bug #53916] Document the TZ environment variable

[Ian McCallion]

URL:
  <http://savannah.gnu.org/bugs/?53916>

                 Summary: Document the TZ environment variable
                 Project: GNU Octave
            Submitted by: ianmcc
            Submitted on: Tue 15 May 2018 08:05:01 PM UTC
                Category: Documentation
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Documentation
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.4.0
        Operating System: Any

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Details:

Section 36.1 of the Octave manual should describe the TZ environment variable.
I suggest something like the following:

The TZ environment variable can be used within a process to override the
system's timezone. Octave functions such as localtime that return the dates
and times in local time use the timezone specified in the TZ environment
variable. Specification of TZ can be found here: 
https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html#TZ-Variable.

Functions affected
------------------
localtime, mktime and lstat functions (and possibly others??) are affected by
the TZ environment variable. 

Note that the Octave interpreter and GUI are not affected by the TZ variable.
Time and date are not directly displayed, except by scripts and where dates
and times are used internally for example in timestamp comparisons UTC is
used.

Windows/Unix differences
------------------------

The TZ feature IS NOT present in Microsoft Windows, and the posix layer
shipped with Octave for Microsoft Windows only partially emulates TZ, for
example on Windows calls to the underlying operating system that display local
times eg system('dir'), these do not return times in the TZ-specified the
timezone whereas (I assume??) the equivalents on unix do. This is unlikely to
be a problem in practice.











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