[datetime.datetime(2012, 1, 1, 0, 0), datetime.datetime(2012, 1, 1, 1, 0)]
[datetime.datetime(2012, 1, 2, 0, 0)]
[datetime.datetime(2012, 1, 3, 0, 0)]
[]
[datetime.datetime(2012, 1, 5, 0, 0)]
Split list of datetimes into days