title: pandas to_datetime not working
body: <p>I can't seem to apply <code>to_datetime</code> to a pandas dataframe column, although I've done it dozens of times in the past. The following code tells me that any random value in the "Date Time" column is a string, after I try to convert it to a timestamp. The <code>'errors=coerce'</code> should convert any parsing errors to <code>'NaT'</code>, but instead I still have <code>'2015-10-10 12:31:04'</code> as a string.</p>
  
  <pre><code>import pandas as pd
  df=pd.read_csv(...)
  df["Date Time"]=pd.to_datetime(df["Date Time"],errors="coerce")
  print str(type(df["Date Time"][9]))+" 1"##########
  </code></pre>
  
  <p>Why would pandas not raise an error, or not convert parsing errors to <code>'NaT'</code>?</p>
  
  <p>Here are a few rows of the csv. The real file has a million rows coming from different sources, so it is possible that date formatting is not uniform, however in that case I would expect datetime to return 'NaT' or raise an error, depending on the error argument.</p>
  
  <pre><code>Accuracy,Activity,Altitude,Bearing,Date Time,Date(GMT),Description,Distance,Latitude,Longitude,Name,Speed,_FileNames,datenum
  ,,null,,,,,,sj,,,,C:/Users/Alexis/Dropbox/Location/Path Tracking Lite/aacy.csv,17054710926
  0.0,,0.0,0.0,,,,0.00292115,50.67713796,4.61960233,,4.5,C:/Users/Alexis/Dropbox/Location/Path Tracking Lite/aars.csv,17054710926
  0.0,,0.0,0.0,2015-01-31 15:10:,,,0.00404488,39.91572515,116.43714731,,5.4,C:/Users/Alexis/Dropbox/Location/Path Tracking Lite/abch.csv,17054710926
  0.0,Walk/Run,0.0,0.0,2015-01-11 10:36:22,,,0,39.94002308,116.43548671,tfdeddd,0.0,C:/Users/Alexis/Dropbox/Location/Path Tracking Lite/abbj.csv,20150111
  0.0,Walk/Run,0.0,0.0,2015-01-11 10:36:24,,,0.00968132,39.93998097,116.43558673,,2.7,C:/Users/Alexis/Dropbox/Location/Path Tracking Lite/abbj.csv,20150111
  0.0,Walk/Run,0.0,0.0,2015-01-11 10:36:26,,,0.00768588,39.94003147,116.43552386,,4.5,C:/Users/Alexis/Dropbox/Location/Path Tracking Lite/abbj.csv,20150111
  0.0,Walk/Run,0.0,0.0,2015-01-11 10:36:28,,,0.00239565,39.94007265,116.43551403,,3.6,C:/Users/Alexis/Dropbox/Location/Path Tracking Lite/abbj.csv,20150111
  </code></pre>