', 'B', 'C']; some entries are missing

               A                         B                         C
    0 2013-01-01 2013-01-01 00:00:00-05:00 2013-01-01 00:00:00+01:00
    1 2013-01-02                       NaT                       NaT
    2 2013-01-03 2013-01-03 00:00:00-05:00 2013-01-03 00:00:00+01:00
    Ú20130101é