Index: django/forms/fields.py
===================================================================
--- django/forms/fields.py	(revision 9536)
+++ django/forms/fields.py	(working copy)
@@ -381,7 +381,11 @@
             # components: date and time.
             if len(value) != 2:
                 raise ValidationError(self.error_messages['invalid'])
-            value = '%s %s' % tuple(value)
+            # To support input formats consisting of a date component only.
+            if value[1] in EMPTY_VALUES:
+                value = value[0]
+            else:
+                value = '%s %s' % tuple(value)
         for format in self.input_formats:
             try:
                 return datetime.datetime(*time.strptime(value, format)[:6])
Index: tests/regressiontests/forms/fields.py
===================================================================
--- tests/regressiontests/forms/fields.py	(revision 9536)
+++ tests/regressiontests/forms/fields.py	(working copy)
@@ -601,6 +601,16 @@
 ...
 ValidationError: [u'Enter a valid date/time.']
 
+DateTimeField supports list input:
+>>> f.clean(['2008-11-22', '14:30'])
+datetime.datetime(2008, 11, 22, 14, 30)
+>>> f.clean(['2008-11-22', ''])
+datetime.datetime(2008, 11, 22, 0, 0)
+>>> f.clean(['2008-11-22'])
+Traceback (most recent call last):
+...
+ValidationError: [u'Enter a valid date/time.']
+
 DateField accepts an optional input_formats parameter:
 >>> f = DateTimeField(input_formats=['%Y %m %d %I:%M %p'])
 >>> f.clean(datetime.date(2006, 10, 25))