If n is positive, return tomorrow's business day opening time.
        Otherwise yesterday's business day's opening time.

        Opening time always locates on BusinessDay.
        Otherwise, closing time may not if business hour extends over midnight.

def _next_opening_time(self, other):
        """
        If n is positive, return tomorrow's business day opening time.
        Otherwise yesterday's business day's opening time.

        Opening time always locates on BusinessDay.
        Otherwise, closing time may not if business hour extends over midnight.
        """
        if not self.next_bday.onOffset(other):
            other = other + self.next_bday
        else:
            if self.n >= 0 and self.start < other.time():
                other = other + self.next_bday
            elif self.n < 0 and other.time() < self.start:
                other = other + self.next_bday
        return datetime(other.year, other.month, other.day,
                        self.start.hour, self.start.minute)