offsets.py 文件源码

def apply(self, other):
        n = self.n
        wkday, days_in_month = tslib.monthrange(other.year, other.month)

        monthsSince = (other.month - self.startingMonth) % 3

        if n <= 0 and monthsSince != 0:
            # make sure you roll forward, so negate
            monthsSince = monthsSince - 3

        if n <= 0 and (monthsSince == 0 and other.day > 1):
            # after start, so come back an extra period as if rolled forward
            n = n + 1

        other = other + relativedelta(months=3 * n - monthsSince, day=1)
        return other