Just created a test smart album to search on date.   The Before did not work.  It found all pics created before the specified date and the same for the After.   Result was all pics in the database.

I was able to use the created on filter but had to enter multiple filters for multiple dates.   That worked.
I then had to use the batch manager, filter on that album and was able to work on all pics in the album.
Although this worked it was very clunky.   

Would really appreciate this in a future release.

Thanks for the response. And thanks for this software,

Mike