title: Time zone field in isoformat
body: <p>I have a timestamp that is supposed to be in EST:</p>
  
  <pre><code>2014-10-06T18:06:40-04:56
  </code></pre>
  
  <p>I understand this first part: <code>2014-10-06T18:06:40</code>, but not <code>-04:56</code>. </p>
  
  <p>What does <code>-04:56</code> mean here?`</p>
  
  <p>Here is how I got that timestamp:</p>
  
  <pre><code>import datetime
  start_time = datetime.datetime(year  = 2014, 
                                 month = 10, 
                                 day   = 6, 
                                 hour  = 18, 
                                 tzinfo = pytz.timezone('US/Eastern'))
  end_time   = start_time + datetime.timedelta(seconds=400)
  </code></pre>
  
  <p>And then:</p>
  
  <pre><code>end_time.isoformat()
  </code></pre>
  
  <p>returns: </p>
  
  <pre><code>2014-10-06T18:06:40-04:56
  </code></pre>