diff --git a/src/pypaperless/models/utils/__init__.py b/src/pypaperless/models/utils/__init__.py
index 197b742..a0dfc20 100644
--- a/src/pypaperless/models/utils/__init__.py
+++ b/src/pypaperless/models/utils/__init__.py
@@ -39,7 +39,7 @@ def _str_to_date(datestr: str) -> date:
 
 def _dateobj_to_str(value: date | datetime) -> str:
     """Parse string from date objects."""
-    return value.isoformat().replace("+00:00", "Z")
+    return value.isoformat()
 
 
 def object_to_dict_value(value: Any) -> Any:
diff --git a/tests/data/v0_0_0.py b/tests/data/v0_0_0.py
index 6689b1c..f053fbd 100644
--- a/tests/data/v0_0_0.py
+++ b/tests/data/v0_0_0.py
@@ -45,7 +45,7 @@
             "matching_algorithm": 1,
             "is_insensitive": True,
             "document_count": 12,
-            "last_correspondence": "2022-10-18T00:00:00Z",
+            "last_correspondence": "2022-10-18T00:00:00+00:00",
             "owner": None,
             "user_can_change": True,
         },
@@ -57,7 +57,7 @@
             "matching_algorithm": 1,
             "is_insensitive": True,
             "document_count": 6,
-            "last_correspondence": "2006-03-07T23:00:00Z",
+            "last_correspondence": "2006-03-07T23:00:00+00:00",
             "owner": None,
             "user_can_change": True,
         },
@@ -69,7 +69,7 @@
             "matching_algorithm": 6,
             "is_insensitive": True,
             "document_count": 3,
-            "last_correspondence": "2022-03-11T00:00:00Z",
+            "last_correspondence": "2022-03-11T00:00:00+00:00",
             "owner": 3,
             "user_can_change": True,
         },
@@ -81,7 +81,7 @@
             "matching_algorithm": 1,
             "is_insensitive": True,
             "document_count": 6,
-            "last_correspondence": "2000-07-18T22:00:00Z",
+            "last_correspondence": "2000-07-18T22:00:00+00:00",
             "owner": None,
             "user_can_change": True,
         },
@@ -93,7 +93,7 @@
             "matching_algorithm": 2,
             "is_insensitive": True,
             "document_count": 20,
-            "last_correspondence": "2023-08-28T00:00:00Z",
+            "last_correspondence": "2023-08-28T00:00:00+00:00",
             "owner": None,
             "user_can_change": True,
         },
@@ -114,10 +114,10 @@
             "title": "Crazy Document",
             "content": "some OCRd text",
             "tags": [],
-            "created": "2011-06-22T00:00:00Z",
+            "created": "2011-06-22T00:00:00+00:00",
             "created_date": "2011-06-22",
-            "modified": "2023-08-08T06:06:35.495972Z",
-            "added": "2023-06-30T05:44:14.317925Z",
+            "modified": "2023-08-08T06:06:35.495972+00:00",
+            "added": "2023-06-30T05:44:14.317925+00:00",
             "archive_serial_number": None,
             "original_file_name": "Scan_2023-06-29_113857.pdf",
             "archived_file_name": "2011-06-22 filename.pdf",
@@ -134,10 +134,10 @@
             "title": "Salty Document",
             "content": "OCRd text from document",
             "tags": [1],
-            "created": "2022-01-07T00:00:00Z",
+            "created": "2022-01-07T00:00:00+00:00",
             "created_date": "2022-01-07",
-            "modified": "2023-12-13T16:15:02.148852Z",
-            "added": "2022-02-12T11:34:50.072000Z",
+            "modified": "2023-12-13T16:15:02.148852+00:00",
+            "added": "2022-02-12T11:34:50.072000+00:00",
             "archive_serial_number": 1,
             "original_file_name": None,
             "archived_file_name": "2022-01-07.pdf",
@@ -147,21 +147,21 @@
                 {
                     "id": 1,
                     "note": "Sample note 1.",
-                    "created": "2023-12-21T18:08:11.481206Z",
+                    "created": "2023-12-21T18:08:11.481206+00:00",
                     "document": 2,
                     "user": 1,
                 },
                 {
                     "id": 2,
                     "note": "Sample note 2.",
-                    "created": "2023-12-21T08:26:33.260968Z",
+                    "created": "2023-12-21T08:26:33.260968+00:00",
                     "document": 2,
                     "user": 2,
                 },
                 {
                     "id": 3,
                     "note": "Sample note 3.",
-                    "created": "2023-12-21T08:26:31.782811Z",
+                    "created": "2023-12-21T08:26:31.782811+00:00",
                     "document": 2,
                     "user": 3,
                 },
@@ -194,10 +194,10 @@
             "title": "Crazy Document",
             "content": "some OCRd text",
             "tags": [],
-            "created": "2011-06-22T00:00:00Z",
+            "created": "2011-06-22T00:00:00+00:00",
             "created_date": "2011-06-22",
-            "modified": "2023-08-08T06:06:35.495972Z",
-            "added": "2023-06-30T05:44:14.317925Z",
+            "modified": "2023-08-08T06:06:35.495972+00:00",
+            "added": "2023-06-30T05:44:14.317925+00:00",
             "archive_serial_number": None,
             "original_file_name": "Scan_2023-06-29_113857.pdf",
             "archived_file_name": "2011-06-22 filename.pdf",
@@ -646,7 +646,7 @@
         "id": 1,
         "task_id": "11112222-aaaa-bbbb-cccc-333344445555",
         "task_file_name": "a.png",
-        "date_created": "2023-12-16T13:06:29.107815Z",
+        "date_created": "2023-12-16T13:06:29.107815+00:00",
         "date_done": None,
         "type": "file",
         "status": "STARTED",
@@ -658,8 +658,8 @@
         "id": 2,
         "task_id": "ffffeeee-9999-8888-7777-ddddccccbbbb",
         "task_file_name": "b.png",
-        "date_created": "2023-12-16T13:06:26.117158Z",
-        "date_done": "2023-12-16T13:06:29.859669Z",
+        "date_created": "2023-12-16T13:06:26.117158+00:00",
+        "date_done": "2023-12-16T13:06:29.859669+00:00",
         "type": "file",
         "status": "SUCCESS",
         "result": "Success. New document id 1780 created",
@@ -670,8 +670,8 @@
         "id": 3,
         "task_id": "abcdef12-3456-7890-abcd-ef1234567890",
         "task_file_name": "c.png",
-        "date_created": "2023-12-16T13:04:28.175624Z",
-        "date_done": "2023-12-16T13:04:32.318797Z",
+        "date_created": "2023-12-16T13:04:28.175624+00:00",
+        "date_done": "2023-12-16T13:04:32.318797+00:00",
         "type": "file",
         "status": "SUCCESS",
         "result": "Success. New document id 1779 created",
@@ -693,7 +693,7 @@
             "password": "**********",
             "first_name": "",
             "last_name": "",
-            "date_joined": "2022-02-11T22:28:25Z",
+            "date_joined": "2022-02-11T22:28:25+00:00",
             "is_staff": True,
             "is_active": False,
             "is_superuser": False,
@@ -708,7 +708,7 @@
             "password": "**********",
             "first_name": "Alpha",
             "last_name": "Centauri",
-            "date_joined": "2023-06-27T15:59:01.975496Z",
+            "date_joined": "2023-06-27T15:59:01.975496+00:00",
             "is_staff": False,
             "is_active": True,
             "is_superuser": False,
@@ -759,7 +759,7 @@
             "password": "**********",
             "first_name": "Omega",
             "last_name": "Weapon",
-            "date_joined": "2022-02-14T13:42:54Z",
+            "date_joined": "2022-02-14T13:42:54+00:00",
             "is_staff": True,
             "is_active": True,
             "is_superuser": True,
@@ -899,7 +899,7 @@
             "password": "**********",
             "first_name": "",
             "last_name": "",
-            "date_joined": "2023-06-27T15:56:39.754859Z",
+            "date_joined": "2023-06-27T15:56:39.754859+00:00",
             "is_staff": False,
             "is_active": True,
             "is_superuser": False,
diff --git a/tests/data/v1_17_0.py b/tests/data/v1_17_0.py
index fd7513d..9c5c300 100644
--- a/tests/data/v1_17_0.py
+++ b/tests/data/v1_17_0.py
@@ -4,7 +4,7 @@
     {
         "id": 1,
         "note": "Sample note 1.",
-        "created": "2023-12-21T18:08:11.481206Z",
+        "created": "2023-12-21T18:08:11.481206+00:00",
         "user": {
             "id": 1,
             "username": "test",
@@ -15,7 +15,7 @@
     {
         "id": 2,
         "note": "Sample note 2.",
-        "created": "2023-12-21T08:26:33.260968Z",
+        "created": "2023-12-21T08:26:33.260968+00:00",
         "user": {
             "id": 2,
             "username": "test",
@@ -26,7 +26,7 @@
     {
         "id": 3,
         "note": "Sample note 3.",
-        "created": "2023-12-21T08:26:31.782811Z",
+        "created": "2023-12-21T08:26:31.782811+00:00",
         "user": {
             "id": 3,
             "username": "test",
diff --git a/tests/data/v2_0_0.py b/tests/data/v2_0_0.py
index a590c3a..e9860f1 100644
--- a/tests/data/v2_0_0.py
+++ b/tests/data/v2_0_0.py
@@ -54,39 +54,39 @@
     "results": [
         {
             "id": 1,
-            "created": "2023-12-11T14:06:49.096456Z",
-            "expiration": "2023-12-18T14:06:49.064000Z",
+            "created": "2023-12-11T14:06:49.096456+00:00",
+            "expiration": "2023-12-18T14:06:49.064000+00:00",
             "slug": "GMIFR9WVPe7a0FAltmrAdmVsrrTzH6Z9yFi2jufhi5yCTAMWfF",
             "document": 1,
             "file_version": "original",
         },
         {
             "id": 2,
-            "created": "2023-12-11T14:06:53.583496Z",
-            "expiration": "2024-01-10T14:06:53.558000Z",
+            "created": "2023-12-11T14:06:53.583496+00:00",
+            "expiration": "2024-01-10T14:06:53.558000+00:00",
             "slug": "Px2h3mrkIvExyTE8M8usrTLv3jtTb4MnLJ4eTAxcjy2FUmuDLq",
             "document": 2,
             "file_version": "original",
         },
         {
             "id": 3,
-            "created": "2023-12-11T14:06:55.984583Z",
+            "created": "2023-12-11T14:06:55.984583+00:00",
             "expiration": None,
-            "slug": "bDnxeQ4UmlFVUYCDrb1KBLbE4HVSW8jw3CLElcwPyAncV5eiIz",
+            "slug": "bDnxeQ4UmlFVUYCDrb1KBLbE4HVSW8jw3CLElcwPyAncV5eiI+00:00",
             "document": 1,
             "file_version": "original",
         },
         {
             "id": 4,
-            "created": "2023-12-11T14:07:01.448813Z",
-            "expiration": "2023-12-12T14:07:01.423000Z",
+            "created": "2023-12-11T14:07:01.448813+00:00",
+            "expiration": "2023-12-12T14:07:01.423000+00:00",
             "slug": "HfzHhDzA03ZQg4t4TAlOuup59qgQA18Zjbb9eOE06PZ8KTjgOb",
             "document": 2,
             "file_version": "archive",
         },
         {
             "id": 5,
-            "created": "2023-12-11T14:11:50.710369Z",
+            "created": "2023-12-11T14:11:50.710369+00:00",
             "expiration": None,
             "slug": "7PIGEZbeFv5yIrnpSVwj1QeXiJu0IZCiEWGIV4aUHQrfUQtXne",
             "document": 1,
@@ -94,7 +94,7 @@
         },
         {
             "id": 6,
-            "created": "2023-12-11T14:11:50.710369Z",
+            "created": "2023-12-11T14:11:50.710369+00:00",
             "expiration": None,
             "slug": "7PIGEZbeFv5yIrnpSVwj1QeXiJu0IZCiEWGIV4aUHQrfUQtXne",
             "document": 1,
@@ -102,7 +102,7 @@
         },
         {
             "id": 7,
-            "created": "2023-12-11T14:11:50.710369Z",
+            "created": "2023-12-11T14:11:50.710369+00:00",
             "expiration": None,
             "slug": "7PIGEZbeFv5yIrnpSVwj1QeXiJu0IZCiEWGIV4aUHQrfUQtXne",
             "document": 1,
@@ -110,7 +110,7 @@
         },
         {
             "id": 8,
-            "created": "2023-12-11T14:11:50.710369Z",
+            "created": "2023-12-11T14:11:50.710369+00:00",
             "expiration": None,
             "slug": "7PIGEZbeFv5yIrnpSVwj1QeXiJu0IZCiEWGIV4aUHQrfUQtXne",
             "document": 1,
diff --git a/tests/data/v2_6_0.py b/tests/data/v2_6_0.py
index fc3fc12..afc337f 100644
--- a/tests/data/v2_6_0.py
+++ b/tests/data/v2_6_0.py
@@ -29,7 +29,7 @@
         "index_last_modified": "2024-03-06T07:10:55.370884+01:00",
         "index_error": None,
         "classifier_status": "OK",
-        "classifier_last_trained": "2024-03-06T07:05:01.281804Z",
+        "classifier_last_trained": "2024-03-06T07:05:01.281804+00:00",
         "classifier_error": None,
     },
 }