pydata/pandas — pull request #3671 by jreback (2013-05-21 17:41:33+00:00)
Title: BUG:  convert_objects with convert_dates=coerce was parsing `a` into a date

this is a 'bug' in dateutil:

```
In [1]: import dateutil

In [2]: dateutil.parser.parse('a')
Out[2]: datetime.datetime(2013, 5, 21, 0, 0)
```