ERR: HDF5 serialization of datelike-object dtypes should raise
UPDATE:

```
In [157]: problem_date = old.dob.loc[4231354]

In [158]: problem_date
Out[158]: datetime.date(2939, 6, 2)

In [159]: test_series = pd.Series([problem_date])

In [160]: pd.to_datetime(test_series)
Out[160]: 
0    2939-06-02
dtype: object
```

It seems this is the source of the problem. I think there may be other dates in my dataset that are breaking the `to_datetime` method

UPDATE 2:

It seems that maybe it's that the date is later than 2900 that's causing the problem?

```
In [194]: pd.to_datetime(old.dob[8230866])                
Out[194]: datetime.date(2955, 8, 22)

In [195]: another_bad_date = old.dob.loc[8230866]         

In [196]: pd.to_datetime(pd.Series([another_bad_date]))
Out[196]: 
0    2955-08-22
dtype: object
```
# 

original issue:

The column in question came from a read_sql query, and the column has datetimes. It consists solely of pandas datetime objects and NoneType objects. I have iterated over the Series to be sure. The column has 11 million rows.

I've tried casting with to_datetime (and the dtype remains object--shouldn't the dtype change after that call?), to no avail.

Here's some stuff I get from poking around after sticking an `import pdb; pdb.set_trace()` into line 3329 of pytables.py (after `except (NotImplementedError, ValueError, TypeError) as e:`):

```
(Pdb) b

(Pdb) i

3

(Pdb) blocks[3]

ObjectBlock: [1, 2, 3, 4, 9, 12, 13, 14], 8 x 8255524, dtype: object

(Pdb) blk_items[3]

Index([u'dob', u'City', u'Region', u'Zip', u'lang', u'UnsubscribedDate', u'BadAddressDate', u'ISP'], dtype='object')

(Pdb) existing_col

(Pdb) col

name->values_block_3,cname->values_block_3,dtype->None,shape->None

(Pdb) b

(Pdb) type(b)

<class 'pandas.core.internals.ObjectBlock'>

(Pdb) block_items

*** NameError: name 'block_items' is not defined

(Pdb) b_items

Index([u'dob', u'City', u'Region', u'Zip', u'lang', u'UnsubscribedDate', u'BadAddressDate', u'ISP'], dtype='object')

(Pdb) existing_col

(Pdb) e

TypeError('Cannot serialize the column [dob] because\nits data contents are [mixed] object dtype',)

(Pdb) type(col)

<class 'pandas.io.pytables.DataCol'>

(Pdb) lib

<module 'pandas.lib' from '/home/mmccrea/anaconda/lib/python2.7/site-packages/pandas/lib.so'>
```

My debugging kinds of hits a wall here, because it seems `infer_dtype` seems to be throwing the error, which is in lib.so, which is a compiled binary and I'm not sure how to look into that to figure out what's going on. I would love a suggestion about how to deal with that in the future, in addition to some answers about what's going on in this case.
