diff --git a/model_utils/fields.py b/model_utils/fields.py
index 989c166..49a3185 100644
--- a/model_utils/fields.py
+++ b/model_utils/fields.py
@@ -33,14 +33,26 @@ class AutoLastModifiedField(AutoCreatedField):
     By default, sets editable=False and default=datetime.now.
 
     """
+    def get_default(self):
+        """Return the default value for this field."""
+        if not hasattr(self, "_default"):
+            self._default = self._get_default()
+        return self._default
 
     def pre_save(self, model_instance, add):
         value = now()
-        if not model_instance.pk:
-            for field in model_instance._meta.get_fields():
-                if isinstance(field, AutoCreatedField):
-                    value = getattr(model_instance, field.name)
-                    break
+        if add:
+            current_value = getattr(model_instance, self.attname, self.get_default())
+            if current_value != self.get_default():
+                # when creating an instance and the modified date is set
+                # don't change the value, assume the developer wants that
+                # control.
+                value = getattr(model_instance, self.attname)
+            else:
+                for field in model_instance._meta.get_fields():
+                    if isinstance(field, AutoCreatedField):
+                        value = getattr(model_instance, field.name)
+                        break
         setattr(model_instance, self.attname, value)
         return value
 
diff --git a/tests/test_models/test_timestamped_model.py b/tests/test_models/test_timestamped_model.py
index cac07f3..9fc884f 100644
--- a/tests/test_models/test_timestamped_model.py
+++ b/tests/test_models/test_timestamped_model.py
@@ -1,6 +1,6 @@
 from __future__ import unicode_literals
 
-from datetime import datetime
+from datetime import datetime, timedelta
 
 from freezegun import freeze_time
 
@@ -30,3 +30,66 @@ class TimeStampedModelTests(TestCase):
             t1.save()
 
         self.assertEqual(t1.modified, datetime(2016, 1, 2))
+
+    def test_overriding_created_via_object_creation_also_uses_creation_date_for_modified(self):
+        """
+        Setting the created date when first creating an object
+        should be permissable.
+        """
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1 = TimeStamp.objects.create(created=different_date)
+        self.assertEqual(t1.created, different_date)
+        self.assertEqual(t1.modified, different_date)
+
+
+    def test_overriding_modified_via_object_creation(self):
+        """
+        Setting the modified date explicitly should be possible when
+        first creating an object, but not thereafter.
+        """
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1 = TimeStamp.objects.create(modified=different_date)
+        self.assertEqual(t1.modified, different_date)
+        self.assertNotEqual(t1.created, different_date)
+
+    def test_overriding_created_after_object_created(self):
+        """
+        The created date may be changed post-create
+        """
+        t1 = TimeStamp.objects.create()
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1.created = different_date
+        t1.save()
+        self.assertEqual(t1.created, different_date)
+
+    def test_overriding_modified_after_object_created(self):
+        """
+        The modified date should always be updated when the object
+        is saved, regardless of attempts to change it.
+        """
+        t1 = TimeStamp.objects.create()
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1.modified = different_date
+        t1.save()
+        self.assertNotEqual(t1.modified, different_date)
+
+    def test_overrides_using_save(self):
+        """
+        The first time an object is saved, allow modification of both
+        created and modified fields.
+        After that, only created may be modified manually.
+        """
+        t1 = TimeStamp()
+        different_date = datetime.today() - timedelta(weeks=52)
+        t1.created = different_date
+        t1.modified = different_date
+        t1.save()
+        self.assertEqual(t1.created, different_date)
+        self.assertEqual(t1.modified, different_date)
+        different_date2 = datetime.today() - timedelta(weeks=26)
+        t1.created = different_date2
+        t1.modified = different_date2
+        t1.save()
+        self.assertEqual(t1.created, different_date2)
+        self.assertNotEqual(t1.modified, different_date2)
+        self.assertNotEqual(t1.modified, different_date)