大熊猫前一天的同一时间

Question

我有一个DatetimeIndex，即：

DatetimeIndex(['2004-01-02 00:00:00', '2004-01-02 00:01:00',
           '2004-01-02 00:02:00', '2004-01-02 00:03:00',
           '2004-01-02 00:04:00', '2004-01-02 00:05:00',
           '2004-01-02 00:06:00', '2004-01-02 00:07:00',
           '2004-01-02 00:08:00', '2004-01-02 00:09:00',
           ...
           '2015-12-31 23:50:00', '2015-12-31 23:51:00',
           '2015-12-31 23:52:00', '2015-12-31 23:53:00',
           '2015-12-31 23:54:00', '2015-12-31 23:55:00',
           '2015-12-31 23:56:00', '2015-12-31 23:57:00',
           '2015-12-31 23:58:00', '2015-12-31 23:59:00'],
          dtype='datetime64[ns]', length=4350240, freq=None)

给定一个索引点i，我想获取同一时间但前一天可用的索引（不是昨天！因为不是所有的天都在索引中）。