public function setValidRange($start_offset, $end_offset)
    {
        // Beginning of this year
        $date = new SwatDate();
        $date->setMonth(1);
        $date->setDay(1);
        $date->setHour(0);
        $date->setMinute(0);
        $date->setSecond(0);
        $date->setTZById('UTC');

        $this->valid_range_start = clone $date;
        $this->valid_range_end = clone $date;

        $year = $date->getYear();
        $this->valid_range_start->setYear($year + $start_offset);
        $this->valid_range_end->setYear($year + $end_offset + 1);
    }