diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 953026dcfe..6b38b2229e 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -443,6 +443,8 @@ class DateField(Field):
         Field.__init__(self, verbose_name, name, **kwargs)
 
     def to_python(self, value):
+        if value is None:
+            return value
         if isinstance(value, datetime.datetime):
             return value.date()
         if isinstance(value, datetime.date):
@@ -505,6 +507,8 @@ class DateField(Field):
 
 class DateTimeField(DateField):
     def to_python(self, value):
+        if value is None:
+            return value
         if isinstance(value, datetime.datetime):
             return value
         if isinstance(value, datetime.date):
diff --git a/tests/modeltests/validation/models.py b/tests/modeltests/validation/models.py
index a9a3d3f485..1066faca4f 100644
--- a/tests/modeltests/validation/models.py
+++ b/tests/modeltests/validation/models.py
@@ -146,4 +146,8 @@ u'john@example.com'
 >>> p.validate()
 {'email': ['Enter a valid e-mail address.']}
 
+# Make sure that Date and DateTime return validation errors and don't raise Python errors.
+>>> Person(name='John Doe', is_child=True, email='abc@def.com').validate()
+{'favorite_moment': ['This field is required.'], 'birthdate': ['This field is required.']}
+
 """}