title: django set session variable till end of day
body: <p>I need to set a session variable that expires at the end of each day.</p>
  
  <p>I know I can set a session variable like this:</p>
  
  <pre><code>request.session['my_variable'] = 'foo'
  </code></pre>
  
  <p>How can I then have this expire at the end of the day?</p>