offsets.py 文件源码

def apply(self, other):
        def _increment(date, n):
            year = date.year + n - 1
            if date.month >= self.month:
                year += 1
            return datetime(year, self.month, 1, date.hour, date.minute,
                            date.second, date.microsecond)

        def _decrement(date, n):
            year = date.year + n + 1
            if date.month < self.month or (date.month == self.month and
                                           date.day == 1):
                year -= 1
            return datetime(year, self.month, 1, date.hour, date.minute,
                            date.second, date.microsecond)

        def _rollf(date):
            if (date.month != self.month) or date.day > 1:
                date = _increment(date, 1)
            return date

        n = self.n
        result = other
        if n > 0:
            result = _increment(result, n)
        elif n < 0:
            result = _decrement(result, n)
        else:
            # n == 0, roll forward
            result = _rollf(result)
        return result