diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index bc6042ae59..8b000d3c2a 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -411,7 +411,7 @@ class DateField(Field):
     def get_db_prep_lookup(self, lookup_type, value):
         if lookup_type == 'range':
             value = [str(v) for v in value]
-        elif lookup_type in ('exact', 'gt', 'gte', 'lt', 'lte', 'ne'):
+        elif lookup_type in ('exact', 'gt', 'gte', 'lt', 'lte', 'ne') and hasattr(value, 'strftime'):
             value = value.strftime('%Y-%m-%d')
         else:
             value = str(value)
diff --git a/tests/modeltests/lookup/models.py b/tests/modeltests/lookup/models.py
index e0c4850ba2..a2c0a14158 100644
--- a/tests/modeltests/lookup/models.py
+++ b/tests/modeltests/lookup/models.py
@@ -58,6 +58,10 @@ Article 4
 >>> Article.objects.filter(headline__startswith='Blah blah').count()
 0L
 
+# Date and date/time lookups can also be done with strings.
+>>> Article.objects.filter(pub_date__exact='2005-07-27 00:00:00').count()
+3L
+
 # in_bulk() takes a list of IDs and returns a dictionary mapping IDs
 # to objects.
 >>> Article.objects.in_bulk([1, 2])