FactoryGirl\Provider\Doctrine\DateIntervalHelper::days PHP Method

    public function days($days)
    {
        if (!is_numeric($days)) {
            throw new \RuntimeException();
        }
        $interval = new \DateInterval('P' . $days . 'D');
        $interval->invert = (int) $this->negative;
        $this->time->add($interval);
        return $this;
    }