Add ``months`` months to ``date``.

        Unfortunately we can't use timedeltas to add months because timedelta counts in days
        and there's no foolproof way to add N months in days without counting the number of
        days per month.

def _add_months(self, date, months):
        """
        Add ``months`` months to ``date``.

        Unfortunately we can't use timedeltas to add months because timedelta counts in days
        and there's no foolproof way to add N months in days without counting the number of
        days per month.
        """
        year = date.year + (date.month + months - 1) // 12
        month = (date.month + months - 1) % 12 + 1
        return datetime.date(year=year, month=month, day=1)