My friend! This is a fantastic use for the great exiftool. Here's a link [0] to their (also good) forums where it's implemented by the author in this one-liner:
exiftool -o . '-Directory<FileModifyDate' '-Directory<DateTimeOriginal' -d $TARGETDIR/%Y/%m_%B/%Y.%m.%d -r $SOURCEDIR
[1] http://archive.today/e4JJQ (archive of [0] for posterity)