anchor.diff:            :parser #'chronicity:parse
             :default default
             :required-p required-p
  -          :if-invalid (or if-invalid
  +          :if-invalid (or (parse-if-invalid if-invalid)
                             (lambda () (say "Error. Invalid timestamp"
                                             :color error-color)))
             :color color
  
positive.code:                          (return nil))
                          ((not parsed-input)
                           (if if-invalid
                               (funcall if-invalid)
                               (say "Invalid value" :color error-color)))
                          (parsed-input
                           (return parsed-input)))))))
  
negative.code:             (prompt msg :default default
                          :required-p required-p
                          :validator (clavier:valid-url)
                          :if-invalid (or (parse-if-invalid if-invalid)
                                          (lambda (&optional value)
                                            (say "Invalid url" :color error-color)))
                          :color color
  