So when getting any date information from QML DocumentGalleryModel for images and videos (may be also for other types) date is not valid.

Test code attached

When checking with tracker-info of image valid dates are there:
$ tracker-info file:///home/tliljend/n900_images/20100902_039.jpg
Defaulting to 'files' service
Results: 23 for '/home/tliljend/n900_images/20100902_039.jpg'
'DC:Format' = 'image/jpeg'
'DC:Type' = 'Image'
'Image:Height' = '1440'
'Image:Width' = '2560'
'Image:Date' = '1283459116'
'Image:CameraMake' = 'Nokia'
'Image:CameraModel' = 'N900'
'Image:Orientation' = '8'
'Image:ExposureProgram' = 'Not defined'
'Image:ExposureTime' = '0.030303030303030304'
'Image:FNumber' = '2.8'
'Image:Flash' = '0'
'Image:FocalLength' = '5.2'
'Image:ISOSpeed' = '123'
'Image:WhiteBalance' = 'Auto white balance'
'File:Name' = '20100902_039.jpg'
'File:Ext' = 'jpg'
'File:Path' = '/home/tliljend/n900_images'
'File:NameDelimited' = '/home/tliljend/n900_images/20100902_039.jpg'
'File:Mime' = 'image/jpeg'
'File:Size' = '480666'
'File:Modified' = '1283448316'
'File:Accessed' = '1283506623'

#date -d @1283459116
Thu Sep 2 23:25:16 EEST 2010
$ date -d @1283448316
Thu Sep 2 20:25:16 EEST 2010
$ date -d @1283506623
Fri Sep 3 12:37:03 EEST 2010