How django time zone works with model.field's auto_now_add

I suppose time zone management was added to Django 1.4, so the problem is quite new.

I used a simple model

class Sample(models.Model):
    ...
    date_generated = models.DateTimeField(auto_now_add = True)

When I try to retrieve a newly created record its fails.

min_datetime = datetime.now() - timedelta(seconds = 300)
sample = Sample.objects.get(date_generated__gte = min_datetime)

and the server issues a warning.

DateTimeField received a naive DateTime (2012-06-29 15:02:15.074000) while time zone support is active.

I figured out two solutions to that problem.

1. Disable time zone management in settings.py

    USE_TZ = False 
   

but this is not always desirable. 2. changing

    date_generated = models.DateTimeField(auto_now_add = True) 

to

    date_generated = models.DateTimeField(default=datetime.now()) 

is the solution that keeps time zone management working