@pivot The lists are updated with your findings. 
And to answer your question:
I don’t have an exact release date, but it’s somewhere between September 21st and November 30th, 2010. There are two German Countdown Calendars: one which is also released in English, German and French, which is mentioned on Bulbapedia and released in October 2008; and one German-exclusive Countdown Calendar from 2010 which isn’t mentioned on Bulbapedia.
Recently when I made my German ‘Pikachu around the World’ part I was also searching for its release date, and all I was able to find was some news on bisafans.de from September 21st, 2010. Since this news is from September 21st, and with 24 cards it’s released before December, I assume it is released somewhere in October like the one from 2008.
Greetz,
Quuador