This fixes failing tests when the timezone is different than utc

There were several problems:
* Time.now returns the systems time, not the users time
* fixtures do not translate dates from timezone to utc, but stores the
  date verbatim
* calling a controller will set the timezone to the preference of the
  current_user. So it could be changed while you do not realize this. I
  fixed the failing test, but problems could be elsewhere

config/environments/test.rb

@@ -34,8 +34,6 @@ Rails.application.configure do
   # Print deprecation notices to the stderr.
   config.active_support.deprecation = :stderr
 
-  config.time_zone = 'UTC'
-
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
 end