Preview Sidebar showing date 1/1/1904

Files copied from flash cards (and USB sticks and FAT/FAT32/SMB/CIFS filesystems) for some reason (not understood) have no Creation Date in Mac OS X. When viewing multiple such image files (e.g. JPEGs) in Preview, with the Sidebar sorted by date, Tiger used to show the modification date of the files in the Sidebar, which was useful. Preview 4.0 in 10.5.1 shows the file's Creation Date in the Sidebar, which is always 1/1/1904. Pretty useless.