So, I have timestamps that look like the following:
20140804:10:00:13.281486
20140804:10:00:13.400113
20140804:10:00:13.555512
20140804:10:00:13.435677
You just have to ensure you denote the format specification properly, and you can use pd.to_datetime to convert them to actual datetimes before sort_values.
pd.to_datetime(stamps, format="%Y%m%d:%H:%M:%S.%f").sort_values()
This is much more direct than decomposing the timestamps in components and performing a multiple-criteria sort as you were attempting.
Demo
>>> stamps
0 20140804:10:00:13.281486
1 20140804:10:00:13.400113
2 20140804:10:00:13.555512
3 20140804:10:00:13.435677
dtype: object
>>> pd.to_datetime(stamps, format="%Y%m%d:%H:%M:%S.%f").sort_values()
0 2014-08-04 10:00:13.281486
1 2014-08-04 10:00:13.400113
3 2014-08-04 10:00:13.435677
2 2014-08-04 10:00:13.555512
dtype: datetime64[ns]