Sort thumbs by date causes issues as for some reason modified or created date doesn't register (to the file) when modified or created (either with DK or other soft). So when sorting images by date some images might be missing from 'the order'. This should be solved bu allowing thumbs to be sorted by i) created date and by ii) modified date. For example XnViewMP masters this very well.
That a creation date does not exist, can never happen. The last fallback is the file date if none of the EXIF, IPTC or XMP metadata could be read. Do you have a screenshot where it can be seen that a image has no creation date? Maik
Can you please test whether the problem with the current developer version is still to reproduce? Reread the metadata of the images to possibly correct the creation date. https://files.kde.org/digikam/ Maik
digiKam 7.0.0 stable release is now published and now available as FlatPak: https://www.digikam.org/news/2020-07-19-7.0.0_release_announcement/ We need a fresh feedback on this file using this version. Thanks in advance Gilles Caulier
Fixed with bug 437897, we now always have a creation date, if the file date is not valid, we use the current date. Maik