title: Convert string to time with python
body: <p>I have read a few stackoverflow posts but still can't figure this out... </p>
  
  <p>I want to crawl craigslist post posted within last 48 hours. Posted time is in the following format for craigslist:</p>
  
  <p>2013-03-15, 7:43PM MDT</p>
  
  <p>I have tried</p>
  
  <pre><code>string = "2013-03-15, 7:43PM MDT"
  
  time.strptime(string, "%Y-%m-%d, %I:%M%p %Z")
  </code></pre>
  
  <p>But apparent the format doesnt match the string. What should be the format for this time string?</p>