title: Python isinstance() returning error with datetime.date
body: <p>I am trying to compile <a href="http://djangosnippets.org/snippets/1151/">an old 2008 code</a>. </p>
  
  <pre><code>import datetime
  
  if isinstance(value, datetime.date):
  </code></pre>
  
  <p>But I got an error: </p>
  
  <blockquote>
    <p>isinstance() arg 2 must be a class,
    type, or tuple of classes and types
    Python Executable:    /usr/bin/python2.6
    Python Version:   2.6.5</p>
  </blockquote>
  
  <p>What am I missing?</p>