Different behaviour on two different environments. TypeError: data type "datetime" not understood
#### I have an aggregation logic

```python
In [19]: datewise_prices
Out[19]: 
[{'arrivalDate': 1490227200000,
  'maxPrice': 3300,
  'minPrice': 3300,
  'modalPrice': 3300},
 {'arrivalDate': 1490400000000,
  'maxPrice': 3300,
  'minPrice': 3300,
  'modalPrice': 3300},
 {'arrivalDate': 1490832000000,
  'maxPrice': 3500,
  'minPrice': 3500,
  'modalPrice': 3500},
 {'arrivalDate': 1490918400000,
  'maxPrice': 3300,
  'minPrice': 3300,
  'modalPrice': 3300},
 {'arrivalDate': 1491091200000,
  'maxPrice': 3300,
  'minPrice': 3300,
  'modalPrice': 3300}]

In [20]: weekly_dataframe = pandas.DataFrame(datewise_prices)
    ...: weekly_dataframe.drop('minPrice', axis=1, inplace=True)
    ...: weekly_dataframe.drop('maxPrice', axis=1, inplace=True)
    ...: weekly_dataframe['arrivalDate'] = pandas.to_datetime(weekly_dataframe['arrivalDate'], unit='ms')
    ...: weekly_dataframe = weekly_dataframe.resample('W', on='arrivalDate')['modalPrice'].mean().dropna().reset_index()
    ...: weekly_dataframe['label'] = (weekly_dataframe['arrivalDate'] - pandas.offsets.DateOffset(days=6)).dt.strftime('%d %b') + ' to ' + weekly_dataframe['arriv
    ...: alDate'].dt.strftime('%d %b')

```
#### It results in an error on my Staging environment but works fine on my local.

The staging environment gives an error in `(weekly_dataframe['arrivalDate'] - pandas.offsets.DateOffset(days=6)).dt.strftime('%d %b')`

```
Traceback (most recent call last):
  File "/root/myapp/myapp/handlers/aggregation_handler.py", line 290, in get_daily_weekly_and_monthly_aggregates
    weekly_dataframe['label'] = (weekly_dataframe['arrivalDate'] - pandas.offsets.DateOffset(days=6)).dt.strftime('%d %b') + ' to ' + weekly_dataframe['arrivalDate'].dt.strftime('%d %b')
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/ops.py", line 696, in wrapper
    converted = _Op.get_op(left, right, name, na_op)
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/ops.py", line 330, in get_op
    return _TimeOp(left, right, name, na_op)
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/ops.py", line 343, in __init__
    lvalues = self._convert_to_array(left, name=name)
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/ops.py", line 454, in _convert_to_array
    if (inferred_type in ('datetime64', 'datetime', 'date', 'time') or
TypeError: data type "datetime" not understood
```

but it works fine on my local.

#### Output of ``pd.show_versions()`` on local

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.6.final.0
python-bits: 64
OS: Linux
OS-release: 4.4.0-78-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_IN
LOCALE: None.None

pandas: 0.19.2
nose: None
pip: 9.0.1
setuptools: 36.0.1
Cython: None
numpy: 1.12.1
scipy: None
statsmodels: None
xarray: None
IPython: 5.4.1
sphinx: None
patsy: None
dateutil: 2.5.3
pytz: 2016.7
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: None
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: 0.9.6
lxml: None
bs4: None
html5lib: 0.999
httplib2: 0.8
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.8
boto: 2.40.0
pandas_datareader: None
</details>

#### Output of ``pd.show_versions()`` on Staging
<details>
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.6.final.0
python-bits: 64
OS: Linux
OS-release: 3.13.0-57-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: None.None

pandas: 0.19.2
nose: None
pip: 1.5.4
setuptools: 3.3
Cython: None
numpy: 1.13.0
scipy: None
statsmodels: None
xarray: None
IPython: 4.0.0
sphinx: None
patsy: None
dateutil: 2.5.3
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: None
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: 0.9.6
lxml: None
bs4: None
html5lib: 0.999
httplib2: None
apiclient: None
sqlalchemy: 1.0.8
pymysql: None
psycopg2: None
jinja2: 2.9.6
boto: 2.40.0
pandas_datareader: None
</details>

Please help me out.