Python for Windows reports wrong local time when run under Cygwin on Europe/Moscow TZ

[Mike Kaganski <mikekaganski@mail.ru>]

Hello,

Running Cygwin 3.1.7-1 on Windows 10 Version 21H1 (OS Build 19043.985), 
I have this issue:

when I start Cygwin's Python, I have correct time reported:

> mikek@DESKTOP-8SHAE9Q ~
> $ python
> Python 3.8.9 (default, Apr 21 2021, 23:14:29)
> [GCC 10.2.0] on cygwin
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import datetime
> >>> datetime.datetime.now()
> datetime.datetime(2021, 6, 7, 9, 40, 15, 318391)

But running Python for Windows (it doesn't matter which, specifically 
for the test I used the one from MS Store [1]), I have incorrect local time:

> mikek@DESKTOP-8SHAE9Q ~
> $ "C:/Program 
> Files/WindowsApps/PythonSoftwareFoundation.Python.3.8_3.8.2800.0_x64__qbz5n2kfra8p0/python3.8.exe"
> Python 3.8.10 (tags/v3.8.10:3d8993a, May  3 2021, 11:48:03) [MSC 
> v.1928 64 bit (AMD64)] on win32
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import datetime
> >>> datetime.datetime.now()
> datetime.datetime(2021, 6, 7, 7, 40, 55, 503775)

Note how the latter output reports 2021-06-07 07:40, while the former 
reports 2021-06-07 09:40. The difference is 2 hours.

Starting the same Python for Windows from cmd.exe has it correct:

> C:\Users\mikek>python
> Python 3.8.10 (tags/v3.8.10:3d8993a, May  3 2021, 11:48:03) [MSC 
> v.1928 64 bit (AMD64)] on win32
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import datetime
> >>> datetime.datetime.now()
> datetime.datetime(2021, 6, 7, 9, 41, 21, 925240)

Cygwin reports correct timezone:

> $ echo $TZ
> Europe/Moscow

Starting Python for Windows using a different timezone (specifically, '$ 
TZ=UTC "C:/Program 
Files/WindowsApps/PythonSoftwareFoundation.Python.3.8_3.8.2800.0_x64__qbz5n2kfra8p0/python3.8.exe"') 
gives correct time for *that* time zone.

This is a problem, because in our project (LibreOffice), we use Cygwin 
as environment for unit testing, where LibreOffice's own Python (also 
built natively for Windows) is used, and at some times (from 00:00 till 
02:00) it reports wrong dates, which makes tests fail locally on 
affected systems(see [2]).

Thank you!


[1] https://www.microsoft.com/en-us/p/python-38/9mssztt1n39l

[2] 
https://gerrit.libreoffice.org/c/core/+/92217/2#message-f55091795e7cde9d75adc00ddb69451121b644f6


-- 

Best regards,

Mike Kaganski