时间处理

1：时间相加减，获取7天前的年月日

 d = datetime.datetime.now()

 d2 = d - datetime.timedelta(days=7)
 dd=d2.date()

2：时间比大小

end_time = datetime.datetime.strptime(
                end_time, '%Y-%m-%d %H:%M:%S')

start_time = datetime.datetime.strptime(
                start_time, '%Y-%m-%d %H:%M:%S')

start_timess = datetime.datetime.strptime(t1, '%Y-%m-%d %H:%M:%S')

end_timess = datetime.datetime.strptime(t2, '%Y-%m-%d %H:%M:%S')

start_timess >= start_time and end_timess <= end_time

3：特殊时间处理“2015-12-7T16:00:00.000Z”

start_time = datetime.datetime.strptime(start_time, "%Y-%m-%dT%H:%M:%S.%fZ") + datetime.timedelta(hours=8)