code: function (noop, date) {
              var _field = $(this.options.AltField);
              if (_field.length) {
                  _field.val( this._formatMonth(date, this.options.AltFormat) );
              }
          }
docs: When calling this method with a falsy (undefined) date value, this.element.val() is used as the date value.  Therefore it's important to update the input field before calling this method.