Resolving ValidationError: [u"'' value has an invalid date format. It must be in YYYY-MM-DD format."] in Django 1.9.2?
<p>Earlier I created two fields &amp; migrated everything. after that I tried to add three fields <code>title</code>,<code>about</code>,<code>birthdate</code> into the model.
I created a model like this :</p>

<pre><code>from __future__ import unicode_literals
from django.utils import timezone
from django.db import models

# Create your models here.

class APP1Model(models.Model):
    name = models.CharField(max_length=120)
    percentage = models.CharField(max_length=120)
    title = models.CharField(max_length=100,default='Title')
    birth_date = models.DateTimeField(blank=True, null=True)
    about = models.TextField(max_length=100,null=True,default='About Yourself')

    def __unicode__(self):
        return self.name
</code></pre>

<p>But when I try to migrate in python shell, it is showing a validation error like this:</p>

<pre><code>Operations to perform:
  Apply all migrations: admin, contenttypes, auth, app1, sessions
Running migrations:
  Applying app1.0005_auto_20160217_1346...Traceback (most recent call last):
  File "manage.py", line 10, in &lt;module&gt;
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 345, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 348, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 399, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 200, in handle
    executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 92, in migrate
    self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 121, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 198, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py", line 123, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/fields.py", line 62, in database_forwards
    field,
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/sqlite3/schema.py", line 221, in add_field
    self._remake_table(model, create_fields=[field])
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/sqlite3/schema.py", line 103, in _remake_table
    self.effective_default(field)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/schema.py", line 210, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/__init__.py", line 728, in get_db_prep_save
    prepared=False)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/__init__.py", line 1301, in get_db_prep_value
    value = self.get_prep_value(value)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/__init__.py", line 1296, in get_prep_value
    return self.to_python(value)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/__init__.py", line 1273, in to_python
    params={'value': value},
django.core.exceptions.ValidationError: [u"'' value has an invalid date format. It must be in YYYY-MM-DD format."]
</code></pre>

<p>How to rectify this? I tried all solution i read here but it doesn't work?</p>

<p>I am using Django: 1.9.2</p>

<p>My migration File</p>

<pre><code>from __future__ import unicode_literals

from django.db import migrations, models
</code></pre>

<p>class Migration(migrations.Migration):</p>

<pre><code>dependencies = [
    ('app1', '0004_auto_20160217_0427'),
]

operations = [
    migrations.AddField(
        model_name='app1model',
        name='about',
        field=models.TextField(default='About Yourself', max_length=100, null=True),
    ),
    migrations.AddField(
        model_name='app1model',
        name='birth_date',
        field=models.DateField(blank=True, default='', null=True),
    ),
    migrations.AddField(
        model_name='app1model',
        name='title',
        field=models.CharField(default='', max_length=100),
    ),
]
</code></pre>