python进行日期年月日的计算

import datetime
from dateutil.relativedelta import relativedelta

class DateFormat:
    """
    通过"year=9&day=-1"，计算得到当前日期偏移对应的年、天之后的日期YYYY-MM-DD;
    """

    def __init__(self,birthday):
        self.birthday = "year=9&day=-1"

    def date_format(self):
        """

        :return: 返回处理后的日期
        """
        now_time = datetime.datetime.now()

        year,day = self.birthday.replace("year=","").replace("day=","").split("&")
        if year=="":
            year=0
        if day=="":
            day=0

        cal_year_day_time = now_time+relativedelta(years=int(year),days=int(day))

        return cal_year_day_time
        
        print(type(now_time))
        print(cal_year_day_time)
        print(datetime.datetime.strptime("2012-02-29",'%Y-%m-%d')+relativedelta(years=10),"9999999999999")

DateFormat("").date_format()