I have been using the option "new and updated file(s) only".
It works great until I noticed large backups for files that already existed. On closer inspections the files that were being replaced were identical except they were modified by 1 hour. Somewhere DST is not being adjusted or accounted for here.
Old bug? I don't know but this one might be unrelated. I don't keep persistent connections up like this guy:
The system dates on both machines are close.
I know my Windows box observes DST. Perhaps my Ubunto box was not during the summer months?