Getting 'can't subtract offset-naive and offset-aware datetimes'

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At a few places in the codebase, I'm getting the error that I can't subtract offset-naive and offset-aware datetimes. I tried fixing it in one place in the source, but ran into it somewhere else. Any advice?

Environment:


Request Method: GET
Request URL: http://ec2-54-242-211-34.compute-1.amazonaws.com/questions/

Django Version: 1.4.1
Python Version: 2.7.3
Installed Applications:
('longerusername',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.sites',
 'django.contrib.staticfiles',
 'django.contrib.admin',
 'django.contrib.humanize',
 'django.contrib.sitemaps',
 'django.contrib.messages',
 'askbot',
 'askbot.deps.django_authopenid',
 'south',
 'askbot.deps.livesettings',
 'keyedcache',
 'robots',
 'django_countries',
 'djcelery',
 'djkombu',
 'followit',
 'tinymce',
 'group_messaging',
 'compressor')
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'askbot.middleware.anon_user.ConnectToSessionMessagesMiddleware',
 'askbot.middleware.forum_mode.ForumModeMiddleware',
 'askbot.middleware.cancel.CancelActionMiddleware',
 'django.middleware.transaction.TransactionMiddleware',
 'askbot.middleware.view_log.ViewLogMiddleware',
 'askbot.middleware.spaceless.SpacelessMiddleware')


Traceback:
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
  111.                         response = callback(request, *callback_args, **callback_kwargs)
File "/usr/local/lib/python2.7/dist-packages/askbot/views/readers.py" in questions
  235.             'update_avatar_data': schedules.should_update_avatar_data(request),
File "/usr/local/lib/python2.7/dist-packages/askbot/schedules.py" in should_update_avatar_data
  11.         if (datetime.today() - user.last_login).days <= 1:

Exception Type: TypeError at /questions/
Exception Value: can't subtract offset-naive and offset-aware datetimes