I posted this before - no answer - so I am reformulating the question more clearly.

Where does iMovie09 store the metadata (date when movie was shot)?

I am importing from iMovieHD-06 and, regardless what I do, the metadata gets lost. I can only see the creation dates of the clips (2010), not the dates when they were shot (2005). On the other hand, iMovie06 clips show the correct date - 2005. I tried importing from the iMovie09 menu, or simply copying the iMovie06 Media folder over to the iMovie09 events folder - no success.

However, when I import the same movie directly into iMovie09 (same DV tape, same camcorder), the clips show the correct date (2005).

Problem partially solved, except that I have other 20 hours of movies. Importing from tape takes 1 hour, copying files / importing from 06 takes 15 min on my machine...