public static function getNonTimestampPks()
	{
		$timestamp_start_name = static::temporal_property('start_column');
		$timestamp_end_name = static::temporal_property('end_column');

		$pks = array();
		foreach(parent::primary_key() as $key)
		{
			if ($key != $timestamp_start_name && $key != $timestamp_end_name)
			{
				$pks[] = $key;
			}
		}

		return $pks;
	}