title: Unknown string format - parsing and converting python datetime string
body: <p>I am trying to convert the below to pandas datetime format using <code>dateutil.parser.parse</code> and <code>strftime</code>:</p>
  
  <pre><code>def getDateTimeFromISO8601String(s):
      d = dateutil.parser.parse(s)
      y = d.strftime('%Y-%m-%d %I-%P')
      print(y)
  
  s = '2018-10-13 01-am'
  getDateTimeFromISO8601String(s)
  </code></pre>
  
  <p>But I'm getting the following error </p>
  
  <blockquote>
    <p>ValueError: ('Unknown string format:', '2018-10-13 01-am'</p>
  </blockquote>