title: Django DateTime field to generate timestamp fields withOUT timezone
body: <p>I am working on a Django application where I need all the postgres represented datetime fields to be saved in UTC (as they should). When I'm creating models with DateTime fields they database representation is generated as "<em>timestamp with time zone</em>". 
  Although I can manually alter the tables to remove the timezone from the fields, I was wondering if the DateTime model field has the ability to not do that - i.e., create "<em>timestamp with out time zone</em>" for some fields.
  Is that possible? Or do I have to alter them tables? 
  Thanks,
  Harel</p>