在datetime模块中有一个timedelta这个方法，它代表两个datetime之间的时间差。、

In [42]: datetime.datetime.now().strftime('%Y-%m-%d %H:%M')

Out[42]: '2017-06-23 17:27'

In [36]: (datetime.datetime.now() + datetime.timedelta(days=-1)).strftime('%Y-%m-%d %H:%M')

Out[36]: '2017-06-22 17:27'

In [37]: (datetime.datetime.now() + datetime.timedelta(days=1)).strftime('%Y-%m-%d %H:%M')

Out[37]: '2017-06-24 17:27'

In [41]: (datetime.datetime.now() + datetime.timedelta(minutes=5)).strftime('%Y-%m-%d %H:%M')

Out[41]: '2017-06-23 17:32'