On user request I've implemented a plugin that allows you to adjust the EXIF camera date of JPEG images (i.e. the "date taken/original" date). This tool works on both individual images and groups of images/folders. Just right click and select "Adjust camera date...".
The operation is undoable while jAlbum is running. Currently (for some reason), the file date is touched to the current date too, but that can be fixed with the external tool "Set file date to camera date".
(Use keys up and down to spin the time)
Before running it, do a core update so you get jAlbum 16.1.4
To install, download and double click the "AdjustCameraDate.jaext" file then run jAlbum again.
What do you think?
Following up with a zip of the full project for this if you wish to peek at it. I've also attached the English text file if you care to translate it to your language. We currently have English, Swedish and Hungarian.