datetime object, when rendered to Django template, was always 6 minutes off.

timezone_and_django.py

class LocalDateTimeField(with_metaclass(models.SubfieldBase, models.DateTimeField)):
    '''A hack/workaround version of DateTimeField that considers the datetime
    from the database as local time.
    '''
    def to_python(self, value):
        from django.utils.dateformat import format
        value = models.DateTimeField.to_python(self, value)
        if isinstance(value, datetime):
            print('-' + repr(value))
            print(strftime('%Y-%m-%d %H:%M:%S.%f', value.timetuple()))
            print(format(value, 'd F Y, H:i'))
            value = value.replace(tzinfo=get_default_timezone())
            print('+' + repr(value))
            print(strftime('%Y-%m-%d %H:%M:%S.%f', value.timetuple()))
            print(format(value, 'd F Y, H:i'))
        return value

# I have a model with a LocalDateTimeField.

obj = MyModel.objects.get(id=1234)

repr(obj.datefield)
# datetime.datetime(2014, 7, 3, 17, 7, 3, tzinfo=<DstTzInfo 'America/Sao_Paulo' LMT-1 day, 20:54:00 STD>)

from django.template import Context,Template
templ = Template('Date: {{ d|date:"d F Y, H:i:s" }}')
templ.render(Context({'d': obj.datefield}))
# 'Date: 03 July 2014, 17:13:03'
# WTF?
# Why the object is 17:07:03 and the printed version from the template is 17:13:03


# The normalize() method was changing the time:
# https://bazaar.launchpad.net/~stub/pytz/devel/view/head:/src/pytz/tzinfo.py#L238

dt.tzinfo._utcoffset
# datetime.timedelta(-1, 75240)

75240 / 60 / 60
# 20.9 hours! WAT?


# Reason: https://stackoverflow.com/questions/18255024/pytz-utcoffset-has-a-wrong-value-for-iran
#
# THIS IS WRONG, don't use it:
# value = value.replace(tzinfo=get_default_timezone())
#
# Solution:
value = get_current_timezone().localize(value.replace(tzinfo=None))
# datetime.datetime(2014, 7, 3, 17, 7, 3, tzinfo=<DstTzInfo 'America/Sao_Paulo' BRT-1 day, 21:00:00 STD>)
# Note it is now BRT, and not LMT.

# See also:
# https://github.com/django/django/blob/1.6.5/django/utils/timezone.py#L298