Music "Year Recorded"

Good afternoon,

i work with quite alot of music and i'm having a problem with the "Year Recorded" tab in finder.

for 99% of the tracks it just show "- -" and some will have the actual date. All tracks are tagged correctly with itunes add on Tuneup.

When i look at a track that shows the date and a track the does not, there is no difference.

i have tried

find . -name '*.DS_Store' -type f -delete

sudo rm ~/Library/Preferences/com.apple.finder.plist; killall -HUP Finder

any suggestions?

thanks