diff --git a/django/forms/widgets.py b/django/forms/widgets.py
index 1ac64ac6b9..bfc4cb25d1 100644
--- a/django/forms/widgets.py
+++ b/django/forms/widgets.py
@@ -295,14 +295,21 @@ class DateTimeInput(Input):
         if format:
             self.format = format
 
-    def render(self, name, value, attrs=None):
+    def _format_value(self, value):
         if value is None:
-            value = ''
+            return ''
         elif hasattr(value, 'strftime'):
             value = datetime_safe.new_datetime(value)
-            value = value.strftime(self.format)
+            return value.strftime(self.format)
+        return value
+
+    def render(self, name, value, attrs=None):
+        value = self._format_value(value)
         return super(DateTimeInput, self).render(name, value, attrs)
 
+    def _has_changed(self, initial, data):
+        return super(DateTimeInput, self)._has_changed(self._format_value(initial), data)
+
 class TimeInput(Input):
     input_type = 'text'
 
@@ -400,11 +407,11 @@ class NullBooleanSelect(Select):
 
     def value_from_datadict(self, data, files, name):
         value = data.get(name, None)
-        return {u'2': True, 
-                True: True, 
-                'True': True, 
-                u'3': False, 
-                'False': False, 
+        return {u'2': True,
+                True: True,
+                'True': True,
+                u'3': False,
+                'False': False,
                 False: False}.get(value, None)
 
     def _has_changed(self, initial, data):
diff --git a/tests/regressiontests/forms/widgets.py b/tests/regressiontests/forms/widgets.py
index 51b3356bed..8f03cff271 100644
--- a/tests/regressiontests/forms/widgets.py
+++ b/tests/regressiontests/forms/widgets.py
@@ -1071,9 +1071,9 @@ included on both widgets.
 >>> w.render('date', datetime.datetime(2006, 1, 10, 7, 30))
 u'<input type="text" class="pretty" value="2006-01-10" name="date_0" /><input type="text" class="pretty" value="07:30:00" name="date_1" />'
 
->>> w._has_changed(datetime.datetime(2008, 5, 5, 12, 40, 00), [u'2008-05-05', u'12:40:00'])
+>>> w._has_changed(datetime.datetime(2008, 5, 6, 12, 40, 00), [u'2008-05-06', u'12:40:00'])
 False
->>> w._has_changed(datetime.datetime(2008, 5, 5, 12, 40, 00), [u'2008-05-05', u'12:41:00'])
+>>> w._has_changed(datetime.datetime(2008, 5, 6, 12, 40, 00), [u'2008-05-06', u'12:41:00'])
 True
 
 # DateTimeInput ###############################################################
@@ -1093,6 +1093,13 @@ u'<input type="text" name="date" value="2007-09-17 12:51:34" />'
 >>> w.render('date', datetime.datetime(2007, 9, 17, 12, 51))
 u'<input type="text" name="date" value="2007-09-17 12:51:00" />'
 
+Use 'format' to change the way a value is displayed.
+>>> w = DateTimeInput(format='%d/%m/%Y %H:%M')
+>>> w.render('date', d)
+u'<input type="text" name="date" value="17/09/2007 12:51" />'
+>>> w._has_changed(d, '17/09/2007 12:51')
+False
+
 # TimeInput ###################################################################
 
 >>> w = TimeInput()