[watani]

To answer your two questions:

1) Yes, both the "Date" field under the Calibre metadata GUI and the Updated field in the title page generated by FFF show the correct date

2) Yes, my system clock is correct

That said, after a computer reboot I can no longer reproduce the issue either for the books in question except that many of them needed one update each before FFF would properly detect that they didn't need to be updated. The common thread between the books that still need one update is that the packaged file date and last update site date are the same (see multiple instances in attached log).

As for the original issue, best guess is that this was a Calibre issue where the metadata became temporarily unreadable to FFF in a way that didn't produce visible errors. Earlier that day a separate problem I had was that Calibre was significantly struggling to update any book using FFF. During that time FFF metadata reading took anywhere from 1-5 minutes and downloading from various websites either was extremely slow or never completed (with each job getting 6 processes in task manager that used almost no CPU). After a reboot Calibre seemed to be working fine except for the aforementioned bug of never recognizing certain books as up-to-date, so it's possible that something happened during that earlier problem which messed up Calibre and needed multiple reboots to fix.