title: convert series of strings to datetimeobjects to extract month and year
body: <p>Using python 3 for ML, one problem I have come across today is this. I have a pandas dataframe with one column containing dates.</p>
  
  <pre><code>data['Allfast time'].head()
  0    31-Dec-14 17:55:00
  1    31-Dec-14 22:55:00
  2    31-Dec-14 09:30:00
  3    01-Jan-15 10:55:00
  4    01-Jan-15 21:15:00
  Name: Allfast time, dtype: object
  </code></pre>
  
  <p>The to_datetime() command gives the following error:</p>
  
  <pre><code>TypeError: object of type 'datetime.time' has no len()
  </code></pre>
  
  <p>How do I create a new column data['month'] that contains the month only, extracted from data['Allfast time']?</p>
  
  <p>Thank you!</p>