You can add the field {pubdate} to the save to disk template. Either to the filename or to the path you use in the template.
You need to edit the pubdates to make sure they are unique. To display full dates with day in the GUI, go to preferences and in the dialogue for Tweaks goto "Control how dates are displayed" and change:
Code:
gui_pubdate_display_format = 'dd MMM yyyy'
Got to preferences and in the dialogue for Saving books to disk, change
Code:
Format dates as: %d %b, %y
Use a save to disk template something like this:
Code:
{authors} - {title} - {pubdate}