updating Debian Wheezy lead to a loss of the dates in KOrganizer. They were
stored in ~/.kde/share/apps/korganizer/std.ics. Clicking on the "+" button and
adding a Akonadi ressource and selecting "Personal Calendar" restored some
data (the birthdays). Only importing the std.ics file restored the data (adding
the data to the Akonadi ressource).
The old KDE version was 4.6.x and now I'm using 4.7.4.