time zone conversions fail

[zed]

It works only with the latest timezone for the region. DST transitions, other timezone changes are not handled correctly. Examples:

• round-trip convert timestamp -> named timezone -> utc

    expected 2002-10-27 05:30:00.000000 UTC+0000
    got        10/27/02 06:30:00.0 +00:00 (UTC)

** convert utc datetime -> named timezone

expected 2002-10-27 01:30:00.000000 EDT-0400
got        10/27/02 01:30:00.0 -05:00 (EST)

• convert utc to local timezone

    expected 2010-06-06 21:29:07.730000 MSD+0400
    got        06/06/10 21:29:07.730000 +04:00 (MSK)
    expected 2010-12-06 20:29:07.730000 MSK+0300
    got        12/06/10 20:29:07.730000 +04:00 (MSK)

• date & time in named time zone

    expected 2002-10-27 00:30:00.000000 EDT-0400
    got        10/27/02 00:30:00.0 -05:00 (EST)

• ambiguous: naive datetime to named timezone - no disambiguation
• non-existing times
• time zones in a distant past

    expected 1915-08-04 22:59:59.000000 WMT+0124
    got        08/04/15 22:59:59.0 +01:00 (CET)
    expected 1933-05-15 01:30:00.000000 AMT+0020
    got        05/15/33 01:30:00.0 +01:00 (CET)
    expected 1933-05-15 03:30:00.000000 NST+0120
    got        05/15/33 03:30:00.0 +01:00 (CET)

Examples are from http://pytz.sourceforge.net/

The code to produce the above output https://gist.github.com/4127162

Note: not all of it probably should be fixed but it is useful to be aware that the issues exist.

[crsmithdev]

Most of the conversion / time zone errors have been fixed in my latest commit. Still remaining are the round-trip errors, and I'm not sure exactly yet what my approach to ambiguous instantiation or non-existent times will be. Addressed a few of the consistency issues in your gist as well.

* round-trip convert timestamp -> named timezone -> utc
    expected 2002-10-27 05:30:00.000000 UTC+0000
    got        10/27/02 06:30:00.0 +00:00 (UTC)
** convert utc datetime -> named timezone
    expected 2002-10-27 01:30:00.000000 EDT-0400
    got        10/27/02 01:30:00.0 -05:00 (EST)
* convert utc to local timezone
    expected 2010-06-06 21:29:07.730000 MSD+0400
    got        06/06/10 21:29:07.730000 +04:00 (MSD)
    expected 2010-12-06 20:29:07.730000 MSK+0300
    got        12/06/10 20:29:07.730000 +03:00 (MSK)
* date & time in named time zone
    expected 2002-10-27 00:30:00.000000 EDT-0400
    got        10/27/02 00:30:00.0 -04:00 (EDT)
* ambiguous: naive datetime to named timezone - no disambiguation
* non-existing times
* time zones in a distant past
    expected 1915-08-04 22:59:59.000000 WMT+0124
    got        08/04/15 22:59:59.0 +01:24 (WMT)
    expected 1933-05-15 01:30:00.000000 AMT+0020
    got        05/15/33 01:30:00.0 +00:20 (AMT)
    expected 1933-05-15 03:30:00.000000 NST+0120
    got        05/15/33 03:30:00.0 +01:20 (NST)

Thanks for the detailed assessment and test code, it was and continues to be extremely helpful.

[zed]

I've updated the gist to mark (remove) fixed items. Current results:

* round-trip convert timestamp -> named timezone -> utc
    expected 2002-10-27 05:30:00.000000 UTC+0000
    got        10/27/02 06:30:00.0 +00:00 (UTC)
** convert utc datetime -> named timezone
    expected 2002-10-27 01:30:00.000000 EDT-0400
    got        10/27/02 01:30:00.0 -05:00 (EST)
* convert utc to local timezone
* date & time in named time zone
* ambiguous: naive datetime to named timezone - no disambiguation
* non-existing times
* time zones in a distant past
** seconds in utcoffset (pytz also fails here, datetime limitation)
Examples are from http://pytz.sourceforge.net/

The current failures might be due to the bug in dateutils see https://gist.github.com/3838828