public function get_dategraded() {
        //TODO: HACK - create new fields (MDL-31379)
        if (is_null($this->finalgrade) and is_null($this->feedback)) {
            return null; // no grade == no date
        } else if ($this->overridden) {
            return $this->overridden;
        } else {
            return $this->timemodified;
        }
    }