title: Get outliers in a DataFrame with date
body: <p>I am new to pandas. I have a DataFrame from a list of datetime objects. 
  I'm looking to get the outlier dates in the set. I tried using the std() 
  functions and google with no luck. :( Any help please?</p>
  
  <pre><code>date_list = []
  for event in get_events():
      date_list.append(event["date"])
  
  event_series = pandas.DataFrame(date_list)
  # get outlier set here.
  </code></pre>
  
  <p>I'm looking for a dataset like</p>
  
  <pre><code>[ 1/1/2000,
  1/2/2000,
  1/3/2000,
  1/4/2000,
  1/1/2005 ]
  </code></pre>
  
  <p>to return 1/1/2005 as an outlier.</p>