title: str to time in python
body: <pre><code>time1 = "2010-04-20 10:07:30"
  time2 = "2010-04-21 10:07:30"
  </code></pre>
  
  <p>How to convert the above from string to time stamp?</p>
  
  <p>I need to subtract the above timestamps <code>time2-time1</code>.</p>