Django ModelField for timezone-naive datetimes

fields.py

import datetime

from django.core import exceptions
from django.db.models import DateTimeField
from django.utils.dateparse import parse_date, parse_datetime
from django.utils.translation import ugettext_lazy as _

from south.modelsinspector import add_introspection_rules
add_introspection_rules([], ["^myproject\.myapp\.fields\.NaiveDateTimeField"])


class NaiveDateTimeField(DateTimeField):
    """ DateTimeField implementation which is explicitly timezone-naive.

    Note:
     - only tested for Postgres backend

    TODO: perhaps update default_error_messages to remove TZ info
    TODO: test support for other database backends

    """

    description = _("Timezone-naive date (with time)")

    def to_python(self, value):
        if value is None:
            return value
        if isinstance(value, datetime.datetime):
            return value
        if isinstance(value, datetime.date):
            return datetime.datetime(value.year, value.month, value.day)

        try:
            parsed = parse_datetime(value)
            if parsed is not None:
                return parsed
        except ValueError:
            raise exceptions.ValidationError(
                self.error_messages['invalid_datetime'],
                code='invalid_datetime',
                params={'value': value},
            )

        try:
            parsed = parse_date(value)
            if parsed is not None:
                return datetime.datetime(parsed.year, parsed.month, parsed.day)
        except ValueError:
            raise exceptions.ValidationError(
                self.error_messages['invalid_date'],
                code='invalid_date',
                params={'value': value},
            )

        raise exceptions.ValidationError(
            self.error_messages['invalid'],
            code='invalid',
            params={'value': value},
        )

    def db_type(self, connection):
        if connection.settings_dict['ENGINE'] == 'django.db.backends.mysql':
            return 'datetime'
        else:
            return 'timestamp'