public function getStepIncrement()
    {
        switch ($this->step) {
            case self::$YEARLY:
                return '+1 year';
                break;
            case self::$MONTHLY:
                return '+1 month';
                break;
            case self::$DAILY:
                return '+1 day';
                break;
            case self::$HOURLY:
                return '+1 hour';
                break;
        }
    }