title: Database returned an invalid value in QuerySet.dates()
body: <p>I get this error on my Ubuntu 12.04 machine with mysql 5.5 after I imported some Wordpress content to Mezzanine's blog_blogpost.</p>
  
  <pre><code>ValueError at /admin/blog/blogpost/
  Database returned an invalid value in QuerySet.dates(). Are time zone definitions and pytz installed?
  
  Request Method: GET
  Request URL:    http://127.0.0.1:8000/admin/blog/blogpost/
  Django Version: 1.6.1
  Exception Type: ValueError
  Exception Value:    
  Database returned an invalid value in QuerySet.dates(). Are time zone definitions and pytz installed?
  Exception Location: /home/me/.mezenv/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py in results_iter, line 1107
  Python Executable:  /home/me/.mezenv/bin/python
  Python Version: 2.7.3
  Python Path:    
  [u'/home/me',
   '/home/me/sai',
   '/home/me/.mezenv/local/lib/python2.7/site-packages/distribute-0.6.24-py2.7.egg',
   '/home/me/.mezenv/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg',
   '/home/me/.mezenv/lib/python2.7',
   '/home/me/.mezenv/lib/python2.7/plat-linux2',
   '/home/me/.mezenv/lib/python2.7/lib-tk',
   '/home/me/.mezenv/lib/python2.7/lib-old',
   '/home/me/.mezenv/lib/python2.7/lib-dynload',
   '/usr/lib/python2.7',
   '/usr/lib/python2.7/plat-linux2',
   '/usr/lib/python2.7/lib-tk',
   '/home/me/.mezenv/local/lib/python2.7/site-packages']
  Server time:    Sat, 25 Jan 2014 13:44:11 +0100
  
  
  Error during template rendering
  
  In template /home/me/.mezenv/local/lib/python2.7/site-packages/grappelli_safe/templates/admin/change_list.html, error at line 140
  </code></pre>
  
  <p>I added to my local_settings.py </p>
  
  <pre><code>import pytz
  from pytz import *
  </code></pre>
  
  <p>and also defined timezone in my.cnf [mysqld]</p>
  
  <pre><code>default-time-zone = "+01:00"
  </code></pre>
  
  <p>but I still get the error unitl I get the line in template:</p>
  
  <p>the tag is:</p>
  
  <blockquote>
    <p>140    {% block date_hierarchy %}{% date_hierarchy cl %}{% endblock %}</p>
  </blockquote>
  
  <p>Appreciate your help to resolve it. </p>