总结 datetime.datetime.now() 是获取当前时间
datetime.datetime.now()+ datetime.timedelta(+3) 就是当天加上3天数
datetime.datetime.now()+ datetime.timedelta(-3) 就是当天减去3天数
datetime.datetime.now()+ datetime.timedelta(hours=3) 加3小时
datetime.datetime.now()+ datetime.timedelta(hours=-3) 减去3小时
datetime.datetime.now()+ datetime.timedelta()
附带转载网页http://egon09.blog.51cto.com/9161406/1840425