diff --git a/netbox/dcim/models/devices.py b/netbox/dcim/models/devices.py
index 31c7b1a1f..6e090e33d 100644
--- a/netbox/dcim/models/devices.py
+++ b/netbox/dcim/models/devices.py
@@ -199,7 +199,7 @@ class DeviceType(ImageAttachmentsMixin, PrimaryModel, WeightMixin):
 
     clone_fields = (
         'manufacturer', 'default_platform', 'u_height', 'is_full_depth', 'subdevice_role', 'airflow', 'weight',
-        'weight_unit', 'end_of_life',
+        'weight_unit',
     )
     prerequisite_models = (
         'dcim.Manufacturer',
diff --git a/netbox/dcim/models/modules.py b/netbox/dcim/models/modules.py
index 4d6407e6b..69aaa482e 100644
--- a/netbox/dcim/models/modules.py
+++ b/netbox/dcim/models/modules.py
@@ -141,7 +141,7 @@ class ModuleType(ImageAttachmentsMixin, PrimaryModel, WeightMixin):
         to_field='module_type'
     )
 
-    clone_fields = ('profile', 'manufacturer', 'weight', 'weight_unit', 'airflow', 'end_of_life')
+    clone_fields = ('profile', 'manufacturer', 'weight', 'weight_unit', 'airflow')
     prerequisite_models = (
         'dcim.Manufacturer',
     )
diff --git a/netbox/utilities/testing/base.py b/netbox/utilities/testing/base.py
index 23dac73c8..4cf6b841b 100644
--- a/netbox/utilities/testing/base.py
+++ b/netbox/utilities/testing/base.py
@@ -6,7 +6,7 @@ from django.contrib.contenttypes.models import ContentType
 from django.contrib.postgres.fields import ArrayField, RangeField
 from django.core.exceptions import FieldDoesNotExist
 from django.db import transaction
-from django.db.models import DateField, JSONField, ManyToManyField, ManyToManyRel
+from django.db.models import DateField, DateTimeField, JSONField, ManyToManyField, ManyToManyRel
 from django.forms.models import model_to_dict
 from django.test import Client
 from django.test import TestCase as _TestCase
@@ -214,8 +214,9 @@ class ModelTestCase(TestCase):
                 elif type(value) is IPNetwork:
                     model_dict[key] = str(value)
 
-                # Convert date values to ISO 8601 strings (as rendered by the REST API)
-                elif type(field) is DateField and value is not None:
+                # Convert date values to ISO 8601 strings (as rendered by the REST API). DateTimeField
+                # subclasses DateField, so exclude it here to preserve existing datetime handling.
+                elif isinstance(field, DateField) and not isinstance(field, DateTimeField) and value is not None:
                     model_dict[key] = value.isoformat()
 
                 # Normalize arrays of numeric ranges (e.g. VLAN IDs or port ranges).