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Date: Tue, 8 Jun 2021 10:37:37 -0700
Message-ID: <CAAHpriO6A+6bLXt0Qe-xpdXT1CiLjk7=7G31cHBtnVJ0kXb2Eg@mail.gmail.com>
Subject: Re: Python for Windows reports wrong local time when run under Cygwin
 on Europe/Moscow TZ
To: cygwin@cygwin.com
From: Keith Thompson via Cygwin <cygwin@cygwin.com>
Reply-To: Keith Thompson <Keith.S.Thompson@gmail.com>
Cc: Keith Thompson <Keith.S.Thompson@gmail.com>
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Sender: "Cygwin" <cygwin-bounces+archive-cygwin=delorie.com@cygwin.com>

There is a known problem with the $TZ environment variable.

Here's a discussion from 2017:
https://cygwin.com/pipermail/cygwin/2017-May/232675.html

The problem is that both Cygwin and Windows use the $TZ environment
variable, but they interpret it differently.

The Windows handling of $TZ (or %TZ%) is documented here:
https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/tzset?view=msvc-160

For example, Pacific Time is represented as TZ=PST8PDT.

In Cygwin, my $TZ is set by default to "America/Los_Angeles".
Any Windows applications that I invoke from Cygwin, if they attempt
to determine the time zone, will behave inconsistently because they
don't see "America/Los_Angeles" as a valid time zone string.

I've worked around this by unsetting TZ in my .bash_profile .
Cygwin applications are still able to determine the correct time zone.

I suggest that Cygwin should *not* set the TZ environment variable.

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