public function setTimestamp($unixtimestamp) {
		$diff = $unixtimestamp - $this->getTimestamp();
		$days = floor($diff / 86400);
		$seconds = $diff - $days * 86400;
		$timezone = $this->getTimezone();
		$this->setTimezone('UTC');
		parent::modify("$days days $seconds seconds");
		$this->setTimezone($timezone);
		return $this;
	}