@Kovid, thx, I'll happily take any change you are willing to accept. Certainly the save to disk is the primary case.
As for making my use cases specific - well yes I am describing the actual issue that I'm personally hitting every week around this behaviour, rather than trying to speak on others behalf.
If you want me to say it, then I doubt that Ron and I are the only users out there who have hit the situation of not being able to find books they have added to Calibre because the date field was "magically" set to something historic. But of course I can't begin to guess how many people that might be, particularly given the fact that only a tiny portion of the userbase even comes to these forums. I know I've raised this topic as a thread myself many months ago, when I couldn't figure out why when I added html based books I had downloaded it didn't show up at the top when I sorted by date added - all because there was an opf file sitting within that folder when I imported.
And now it is additionally hitting me because I learnt from a few months with Calibre that sticking all your years of mish-mash of books in a library at once leaves you with just as big a mess and a slow library to try to do something about it
So now I transfer them a few at a time from the old library into a new one to clean them up, but I can't easily see which ones I just copied across - such as if I get interrupted or come back to it on another day. Specific to me - yup, guilty