15. feb 2001
dez 19ter-15. '01
januar - dezember '04
etc. it's german date formats ;).
It is of course not easily to be seen by users that they can use pretty complex pattern - but since it was a web application that was no problem with some hints next to the input field.
My conclusion would be, that I could see, how this type of date (-range) input could work out well for a blog archive or article search instead of displaying calendars or using 3 text input field as in your simple example.
(what does email notification in your comments form mean at all? *checking*) :p