Django migration from `time without time zone` to `timestamp with time zone`

migration.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.db import models, migrations


class Migration(migrations.Migration):

    dependencies = [
        ('offers', '0001_initial'),
    ]

    operations = [
        migrations.RunSQL(
            sql="""
            ALTER TABLE offers_offer
            ALTER COLUMN time TYPE timestamp with time zone
            USING to_timestamp('2014-04-01 ' || time, 'YYYY-MM-DD HH24:MI:SS');
            """,
            reverse_sql="""
            ALTER TABLE offers_offer
            ALTER COLUMN time TYPE time without time zone;
            """,
            state_operations=[migrations.AlterField(
                model_name='offer',
                name='time',
                field=models.DateTimeField(verbose_name='Offer time'),
                preserve_default=True
            )]
        ),
    ]