Date as three-tuple of numbers

def as_tuple(self):
        """Date as three-tuple of numbers"""
        if self._tuple is None:
            # extract leading digits from year
            year = 9999
            if self.year:
                m = self.DIGITS.match(self.year)
                if m:
                    year = int(m.group(0))
            month = self.month_num or 99
            day = self.day if self.day is not None else 99

            # should we include calendar name in tuple too?
            self._tuple = year, month, day

        return self._tuple