Python獲取今天時間：

>>> datetime.datetime.now()
datetime.datetime(2018, 10, 19, 21, 13, 46, 577073)
>>> import time
>>> time.strftime('%Y%m%d')
'20181019'
>>> int (time.strftime('%Y%m%d'))
20181019

昨天時間：

>>> datetime.datetime.now()+datetime.timedelta(days=-1)
datetime.datetime(2018, 10, 18, 21, 16, 3, 441169)
 

明天時間：

>>> datetime.datetime.now()+datetime.timedelta(days=1)
datetime.datetime(2018, 10, 20, 21, 16, 29, 94762)

n天時間：

>>> datetime.datetime.now()+datetime.timedelta(days=n)