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Re: get_date returning false


From: Ian Abbott
Subject: Re: get_date returning false
Date: Fri, 08 Apr 2005 18:28:27 +0100
User-agent: Mozilla Thunderbird 1.0.2 (Windows/20050317)

On 08/04/2005 16:05, Derek Price wrote:
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Ian Abbott wrote:

| If you want to try and reproduce it, you'll probably need to set
| the TZ environment variable. Mine is set to "Europe/London", but if
|  your libc doesn't understand that format, you can try
| "GMT0BST,M3.5.0,M10.5.0" or "GMT0BST" instead.

Is one of these formats likely to be portable?  I could add this to
the test suite, then...

The TZ environment variable has evolved over the years. Old Unix systems only supported the STD<offset>[DST[<offset>]] format like my "GMT0BST" above, so that format is the most portable, but the daylight savings rules are incorrect, except in the US (and Canada?). The "daylight savings rules" part of the TZ variable were added in later Unix versions (I first encountered it in IBM AIX). If the daylight savings rules section was left off, the system defaulted to US daylight savings rules. The full format is described in the tzset(3) manpage or the environ(5) manpage (for the TZ variable).

The modern "Europe/London" format uses a database of timezone rules over history for each geographic and/or political region. This is known as the "tz" or "zoneinfo" database and is used in most modern Unix systems. Read more about it here: <http://www.twinsun.com/tz/tz-link.htm>.

--
-=( Ian Abbott @ MEV Ltd.    E-mail: <address@hidden>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-




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