I'm not really seeing where I'm going wrong here, especially since I hit upon a minor variation at one point that allowed this, but couldn't explain why it worked. Please also tell me, in a more overall sense, what the issue is in general when you are having casting problems of a Java class to a Clojure Interface Function (IFn) and how you can debug it. Thank you.
(defn date
[]
(new java.util.Date))
(defn x
[]
(.format(java.text.SimpleDateFormat "YYYY-MM-DD")(new java.util.Date)))