I've uploaded a new version of the plugin, 1.1.1, which substitutes the current time if it can't parse the timestamp from My Clippings.txt. This will at least allow you to fetch your annotations.
Sadly the date is not the end of the internationalization problems. I still can not fetch my annotations, but I get a new error:
c:\dokume~1\axel\lokale~1\temp\calibre_annotations_plugin\Kindle.py:_parse_my_clippings(failed with line: u'- Ihre Notiz auf Seite 14 | Position 203 | Hinzugef\xfcgt am Sonntag, 2. September 2012 um 00:40:38 Uhr\n')
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Traceback ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Traceback (most recent call last):
File "c:\dokume~1\axel\lokale~1\temp\calibre_annotations_plugin\Kindle.py", line 406, in _parse_my_clippings
AttributeError: 'NoneType' object has no attribute 'group'
Note that instead of "Location" German Kindle uses "Position".
In general that will create more problems than it solves. For example "Position" is also an English word, so it is no surprise the Microsoft translation keeps it. Expecting a translation to always use "Location" when there are a lot of synonymous words would be naive. Auto-translation may work for the date/time, but I see some irregularities in the translations. Sometimes it translates one way, sometimes another. Who knows, tomorrow it may use something else again.
For .net I would try to use the built in "Culture" support. Python may have something similar? IIRC the Unix world often calls it "locale".
Also note that if you tackle internationalization, you also will have to adjust the constants 'Highlight', 'Bookmark', and 'Note' in lines 345 ff in Kindle.py.
I use Sigil to do the (ePub) editing. It has full-text search, so it's pretty quick to pull up the annotations (either in Calibre or on the iPad), then find the corresponding point in Sigil and correct it.
I tried doing this using the Kindle PW, but it was ultimately an exercise in frustration. The interface is just too slow for making annotations.
I find PW acceptable to highlight some place where an edit is needed.
I'm more annoyed by having to use text search to locate a highlight in Sigil. There is the click-work for copy, paste and search. That's ok if you have just a few edits to do. But do it a 100 times and it becomes annoying.
And there is the problem of ambiguity. An extreme example would be if I highlight an extra word "a" in the text. When I see it at the location, it becomes obvious why I marked it. But searching all "a" in the book takes some time. Some (approximate) support for "Go to location" would help.
But I guess that is another topic.
Thanks for your feedback and for trying to quick-fix the problem.