Using Python dateutil to get Large Date Offsets

My program reads six digit dates, yymmdd, as 19yymmdd. I adjust these 19yymmdd dates to 20yymmdd as follows:

        self.DoB = datetime.strptime(line[27:35], "%Y%m%d")

        if self.DoB < datetime(2000, 01, 01):
            self.DoB += relativedelta(years=100)