title: python compare datetimes with different timezones
body: <p>I'm implementing feature with scheduled publishing of object. 
  User chooses the time to publish and i created a cron task to run every minute and check if it's the time to publish. </p>
  
  <p>Users are from different timezones.</p>
  
  <p>So i need to compare two datetimes:</p>
  
  <pre><code>&gt;&gt;user_chosen_time
  datetime.datetime(2012, 12, 4, 14, 0, tzinfo=tzinfo(120))
  &gt;&gt;curdate=datetime.datetime.now()
  datetime.datetime(2012, 12, 4, 18, 4, 20, 17340)
  &gt;&gt;user_chosen_time==curdate
  *** TypeError: can't compare offset-naive and offset-aware datetimes
  </code></pre>
  
  <p>Sorry for rather stupid question but i need to discuss this. Thanks</p>