title: Django datetime migration error
body: <p>I don't think anything in my model has changed. I have reverted it back to times when it was all fully functional and I still get the following errors.</p>
  
  <p>There are my models:</p>
  
  <pre><code>class UserProfile(models.Model):
      # This line is required. Links UserProfile to a User model instance.
      user = models.OneToOneField(User)
  
      # The additional attributes we wish to include.
      website = models.URLField(blank=True)
      picture = models.ImageField(upload_to='profile_images', blank=True)
  
  
      # Override the __unicode__() method to return out something meaningful!
      def __unicode__(self):
          return self.user.username
  
  
  # Could create more post classes, or introduce foreign keys. Unsure as of now.
  class Post(models.Model):
      title = models.CharField(max_length = 140)
      body = models.TextField()
      date = models.DateTimeField(blank=True)
  
      INTRODUCTION = 'I'
      STORIES = 'S'
      CATEGORY_CHOICES = (
          (STORIES, 'Stories'),  # Variable name and display value
          (INTRODUCTION, 'Introduce Yourself'),
      )
  
      category = models.CharField(max_length=1,
                                  choices=CATEGORY_CHOICES,
                                  default=INTRODUCTION)
  
  
      def __unicode__(self):
          return self.title
  
  
  class Photo(models.Model):
      title = models.CharField(max_length = 140)
      photo = models.ImageField(upload_to='user_images', blank=True, null=True)
      date = models.DateTimeField(blank=True)
  
      description = models.TextField()
  
      def __unicode__(self):
          return self.title
  </code></pre>
  
  <p>Upon running manage.py migrate I am confronted with the following error. Having checked the other answers, it seems it was something to do with datetime being used incorrectly but even if I remove date and the DateTime field altogether the error still persists. Does anyone have any ideas?</p>
  
  <p>Thank very much for your help.</p>
  
  <pre><code>Operations to perform:
    Apply all migrations: contenttypes, admin, sessions, auth, blog
  Running migrations:
    Applying blog.0007_auto_20141201_0034...Traceback (most recent call last):
    File "manage.py", line 10, in &lt;module&gt;
      execute_from_command_line(sys.argv)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
      utility.execute()
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/__init__.py", line 377, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/base.py", line 288, in run_from_argv
      self.execute(*args, **options.__dict__)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/base.py", line 338, in execute
      output = self.handle(*args, **options)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/commands/migrate.py", line 160, in handle
      executor.migrate(targets, plan, fake=options.get("fake", False))
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/migrations/executor.py", line 63, in migrate
      self.apply_migration(migration, fake=fake)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/migrations/executor.py", line 97, in apply_migration
      migration.apply(project_state, schema_editor)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/migrations/migration.py", line 107, in apply
      operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/migrations/operations/fields.py", line 37, in database_forwards
      field,
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/backends/sqlite3/schema.py", line 160, in add_field
      self._remake_table(model, create_fields=[field])
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/backends/sqlite3/schema.py", line 74, in _remake_table
      self.effective_default(field)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/backends/schema.py", line 183, in effective_default
      default = field.get_db_prep_save(default, self.connection)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/fields/__init__.py", line 627, in get_db_prep_save
      prepared=False)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/fields/__init__.py", line 1286, in get_db_prep_value
      value = self.get_prep_value(value)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/fields/__init__.py", line 1269, in get_prep_value
      value = super(DateTimeField, self).get_prep_value(value)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/fields/__init__.py", line 1171, in get_prep_value
      return self.to_python(value)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/fields/__init__.py", line 1228, in to_python
      parsed = parse_datetime(value)
    File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/utils/dateparse.py", line 70, in parse_datetime
      match = datetime_re.match(value)
  TypeError: expected string or buffer
  </code></pre>
  
  <p>Here is 'blog.0007...' migration that seems to be failing. To clarify what is going on I was attempting to add a few attributes in order to tell who posted, and at what time etc. Clearly something is not going according to plan..</p>
  
  <pre><code># -*- coding: utf-8 -*-
  from __future__ import unicode_literals
  
  from django.db import models, migrations
  from django.conf import settings
  
  
  class Migration(migrations.Migration):
  
      dependencies = [
          migrations.swappable_dependency(settings.AUTH_USER_MODEL),
          ('blog', '0006_auto_20141201_0027'),
      ]
  
      operations = [
          migrations.AddField(
              model_name='post',
              name='created_by',
              field=models.ForeignKey(default=0, related_name='created_by', to=settings.AUTH_USER_MODEL),
              preserve_default=False,
          ),
          migrations.AddField(
              model_name='post',
              name='created_on',
              field=models.DateTimeField(default=0, auto_now_add=True),
              preserve_default=False,
          ),
          migrations.AddField(
              model_name='post',
              name='edited_by',
              field=models.ForeignKey(default=0, related_name='edited_by', to=settings.AUTH_USER_MODEL),
              preserve_default=False,
          ),
          migrations.AddField(
              model_name='post',
              name='edited_on',
              field=models.DateTimeField(default=0, auto_now=True),
              preserve_default=False,
          ),
          migrations.AddField(
              model_name='post',
              name='published',
              field=models.BooleanField(default=None),
              preserve_default=True,
          ),
      ]
  </code></pre>