docs: function (dt, format) {
              var ret = "";
              if (isInstanceOf(dt, SQL.Time)) {
                  ret = this.timeToString(dt, format);
              } else if (isInstanceOf(dt, SQL.Year)) {
                  ret = this.yearToString(dt, format);
              } else if (isInstanceOf(dt, SQL.DateTime)) {
                  ret = this.dateTimeToString(dt, format);
              } else if (isInstanceOf(dt, SQL.TimeStamp)) {
                  ret = this.timeStampToString(dt, format);
              } else if (isDate(dt)) {
                  ret = dateFormat(dt, format || this.dateFormat);
              }
              return ret;
          }