@BetterRed,
I decided the lazy way, there are dependencies in database (which prevents to change directly the last_modified field, and I don't want to spend time to look at them in the code.
I simply removed all my libbrary, restored a 2 months old DB (with the books) of that time.
A few books (less than 10) are missing, but it will be easy to find which ones, as I removed them from ZZ-TODO on
https://ebooks.raoult.com when I moved them to my own DB.
I will compare the missing files in ZZ-TOTO to those present 2 months ago, so I will take seconds to add them again.
I changed also the template to export to disk to:
{languages}/{:'format_date(raw_field('last_modified'),'yyyyMMd dhhmm')'}-{author_sort} - {series:|(| } {series_index:0>2s|#|) - }{title}
There was no other way to get a full date/time for last_modified, as interface "Export to Disk", the field "File Format to save" is just a limited one, with only %Y, %b, %m, %d available (year, month name, month number, and day number). I don't understand why they don't use the same format as format_date() function, as the function exists.
First I will create DB for the 2 sets in ZZ-TODO to remove the duplicates with my own library, I believe there are thousands. Not urgent, I will improve my own backup script first,
Subject closed then..
br.