I think I uncovered a problem with using custom property dates formatted when formatted as "date" instead of "text" with SW2015. This did not occur until recently - possibly when we switched to SW2015 from SW2014.
Open a new drawing, add a custom property date (ex. - drawnby date) formatted as date. Save the file and reopen it. Then check the just-added date. The date has receded by one day. Our VAR verified the action and is checking with SW.
The temporary fix appears to be to reformat the date as "text" instead.