private function calc(DateTime $base, DateTime $datetime = null, $detailLevel = 1)
	{
		$this->translator = $base->getTranslator();

		$datetime = is_null($datetime) ? DateTime::now() : $datetime;
		$detailLevel = intval($detailLevel);

		$diff = $this->diffInUnits($base->diff($datetime, true), $detailLevel);

		$item = 'just_now';

		if (!$this->isNow($diff))
		{
			$item = $base->isAfter($datetime) ? 'in' : 'ago';
		}

		return array($item, $diff);
	}