title: Started to get an error with pandas.to_datetime
body: <p>I am trying to convert a pandas dataframe column to datetime. It was working perfectly until I uninstall and install python again. I am using Python 2.7.10, Anaconda 2.4.0 (64-bit). Pandas version '0.17.1'.  Here is my code:</p>
  
  <pre><code>import os, sys
  from datetime import date, timedelta
  import pandas as pd
  import numpy as np
  fdf = pd.read_csv(f,delimiter='\t')
  fdf['ORDER_DATETIME']=pd.to_datetime(fdf['ORDER_DATETIME'],"%Y/%m/%d %H:%M")
  </code></pre>
  
  <p>I get the following error message:</p>
  
  <blockquote>
    <p>File "...\AppData\Local\Continuum\Anaconda2\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 71, in execfile
        exec(compile(scripttext, filename, 'exec'), glob, loc)</p>
    
    <p>File ".../filename.py", line 245, in 
        fdf['ORDER_DATETIME']=pd.to_datetime(fdf['ORDER_DATETIME'],"%Y/%m/%d %H:%M")</p>
    
    <p>File "C...\AppData\Local\Continuum\Anaconda2\lib\site-packages\pandas\util\decorators.py", line 89, in wrapper
        return func(*args, **kwargs)</p>
    
    <p>File "...\AppData\Local\Continuum\Anaconda2\lib\site-packages\pandas\tseries\tools.py", line 276, in to_datetime
        unit=unit, infer_datetime_format=infer_datetime_format)</p>
    
    <p>File "...\AppData\Local\Continuum\Anaconda2\lib\site-packages\pandas\tseries\tools.py", line 390, in _to_datetime
        values = _convert_listlike(arg._values, False, format)</p>
    
    <p>File "...\AppData\Local\Continuum\Anaconda2\lib\site-packages\pandas\tseries\tools.py", line 372, in _convert_listlike
        require_iso8601=require_iso8601)</p>
    
    <p>File "pandas\tslib.pyx", line 1847, in pandas.tslib.array_to_datetime (pandas\tslib.c:37155)</p>
    
    <p>File "pandas\tslib.pyx", line 1864, in pandas.tslib.array_to_datetime (pandas\tslib.c:33604)</p>
    
    <p>AssertionError</p>
  </blockquote>