You can certainly add the date, and if you want to, you can with (a lot more) JavaScript convert the device independent path to a Windows path. To add the date, just use these lines instead:
var thePath = this.path;
var theDate = util.printd("mm/dd/yyyy", new Date());
event.value = thePath + " " + theDate;
If you want to work on the windows path, take a look at this page, which explains what the device independent paths are and how they work:
https://acrobatusers.com/tutorials/file-paths-acrobat-javascript
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com