Actually, the problem may be a bit different. It is not the Calibre files or their "internal" dates that are wrong (actually, they might be that is not exactly the issue). The files when looked at using Explorer have the wrong dates. They appear to have been created or placed into the Kindle 8 hours ahead. I have to presume that the kindle as it writes the files into the folders is using the wrong time. It is certainly not using the CLOCK that it displays when I'm reading a book and press MENU. The kindle obviously has two timers or clocks. One for its internal working and stamping files as they are created or modified (the MBP which obviously keeps track of where I am in a book) is stamped with the wrong time - about 8 hours ahead of the display clock and the time where I live.
It just so happened that I had just woken the k3 up and so that files shipped by Calibre arrived and wound up with the wrong dates, too.