I just found the reason for the date change.
PM uses the SHORT FORM date, not the long form date. But the short form date on my computer was shown as dd/mm/yyyy, while the long form was shown as yyyy-mm-dd. So from the look of the date format I thought PM was using the LONG FORM date.
I don't recall changing the date, or other settings that could affect that, but obviously I did change something that affected the date format.
Jim