diff --git a/resend/automations/_automation.py b/resend/automations/_automation.py
index 541f608..4e99be4 100644
--- a/resend/automations/_automation.py
+++ b/resend/automations/_automation.py
@@ -118,11 +118,11 @@ class AutomationRunStep(TypedDict):
     """
     started_at: Union[str, None]
     """
-    When the step started executing (ISO 8601 format), or None if not started.
+    When the step started executing, or None if not started.
     """
     completed_at: Union[str, None]
     """
-    When the step completed executing (ISO 8601 format), or None if not completed.
+    When the step completed executing, or None if not completed.
     """
     output: Any
     """
@@ -134,7 +134,7 @@ class AutomationRunStep(TypedDict):
     """
     created_at: str
     """
-    When the run step was created (ISO 8601 format).
+    When the run step was created.
     """
 
 
@@ -164,11 +164,11 @@ class AutomationListItem(TypedDict):
     """
     created_at: str
     """
-    When the automation was created (ISO 8601 format).
+    When the automation was created.
     """
     updated_at: str
     """
-    When the automation was last updated (ISO 8601 format).
+    When the automation was last updated.
     """
 
 
@@ -205,11 +205,11 @@ class Automation(TypedDict):
     """
     created_at: str
     """
-    When the automation was created (ISO 8601 format).
+    When the automation was created.
     """
     updated_at: str
     """
-    When the automation was last updated (ISO 8601 format).
+    When the automation was last updated.
     """
     steps: List[AutomationResponseStep]
     """
@@ -243,15 +243,15 @@ class AutomationRunListItem(TypedDict):
     """
     started_at: Union[str, None]
     """
-    When the run started (ISO 8601 format), or None.
+    When the run started, or None.
     """
     completed_at: Union[str, None]
     """
-    When the run completed (ISO 8601 format), or None.
+    When the run completed, or None.
     """
     created_at: str
     """
-    When the run was created (ISO 8601 format).
+    When the run was created.
     """
 
 
@@ -283,15 +283,15 @@ class AutomationRun(TypedDict):
     """
     started_at: Union[str, None]
     """
-    When the run started (ISO 8601 format), or None.
+    When the run started, or None.
     """
     completed_at: Union[str, None]
     """
-    When the run completed (ISO 8601 format), or None.
+    When the run completed, or None.
     """
     created_at: str
     """
-    When the run was created (ISO 8601 format).
+    When the run was created.
     """
     steps: List[AutomationRunStep]
     """
diff --git a/resend/contact_properties/_contact_property.py b/resend/contact_properties/_contact_property.py
index 73ea952..751d79c 100644
--- a/resend/contact_properties/_contact_property.py
+++ b/resend/contact_properties/_contact_property.py
@@ -11,7 +11,7 @@ class ContactProperty(TypedDict):
         id (str): The unique identifier for the contact property
         key (str): The key name of the property
         object (str): The object type, always "contact_property"
-        created_at (str): The ISO 8601 timestamp when the property was created
+        created_at (str): The timestamp when the property was created
         type (str): The data type of the property (e.g., "string", "number")
         fallback_value (Union[str, int, float, None]): The default value used when a contact doesn't have this property set
     """
@@ -30,7 +30,7 @@ class ContactProperty(TypedDict):
     """
     created_at: str
     """
-    The ISO 8601 timestamp when the property was created.
+    The timestamp when the property was created.
     """
     type: str
     """
diff --git a/resend/contacts/imports/_contact_import.py b/resend/contacts/imports/_contact_import.py
index 992d48d..96fd679 100644
--- a/resend/contacts/imports/_contact_import.py
+++ b/resend/contacts/imports/_contact_import.py
@@ -32,7 +32,7 @@ class ContactImport(BaseResponse):
         object (str): Always 'contact_import'.
         id (str): Unique identifier for the contact import.
         status (str): 'queued', 'in_progress', 'completed', or 'failed'.
-        created_at (str): ISO 8601 timestamp of when the import was created.
+        created_at (str): Timestamp of when the import was created.
         counts (ContactImportCounts): Row-level import statistics (present when status is completed or failed).
     """
 
diff --git a/resend/events/_event.py b/resend/events/_event.py
index 6ae9935..b19e5c9 100644
--- a/resend/events/_event.py
+++ b/resend/events/_event.py
@@ -41,11 +41,11 @@ class EventListItem(TypedDict):
     """
     created_at: str
     """
-    When the event was created (ISO 8601 format).
+    When the event was created.
     """
     updated_at: Union[str, None]
     """
-    When the event was last updated (ISO 8601 format), or None.
+    When the event was last updated, or None.
     """
 
 
@@ -80,9 +80,9 @@ class Event(TypedDict):
     """
     created_at: str
     """
-    When the event was created (ISO 8601 format).
+    When the event was created.
     """
     updated_at: Union[str, None]
     """
-    When the event was last updated (ISO 8601 format), or None.
+    When the event was last updated, or None.
     """
diff --git a/resend/webhooks/_webhook.py b/resend/webhooks/_webhook.py
index 0fc20c4..caf0aa5 100644
--- a/resend/webhooks/_webhook.py
+++ b/resend/webhooks/_webhook.py
@@ -100,7 +100,7 @@ class Webhook(TypedDict):
     """
     created_at: str
     """
-    When the webhook was created (ISO 8601 format)
+    When the webhook was created
     """
     status: WebhookStatus
     """
diff --git a/tests/api_keys_async_test.py b/tests/api_keys_async_test.py
index c258805..c1f8c6b 100644
--- a/tests/api_keys_async_test.py
+++ b/tests/api_keys_async_test.py
@@ -41,7 +41,7 @@ async def test_api_keys_list_async(self) -> None:
                     {
                         "id": "91f3200a-df72-4654-b0cd-f202395f5354",
                         "name": "Production",
-                        "created_at": "2023-04-08T00:11:13.110779+00:00",
+                        "created_at": "2023-04-08 00:11:13.110779+00",
                     }
                 ]
             }
@@ -51,7 +51,7 @@ async def test_api_keys_list_async(self) -> None:
         for key in keys["data"]:
             assert key["id"] == "91f3200a-df72-4654-b0cd-f202395f5354"
             assert key["name"] == "Production"
-            assert key["created_at"] == "2023-04-08T00:11:13.110779+00:00"
+            assert key["created_at"] == "2023-04-08 00:11:13.110779+00"
 
     async def test_should_list_api_key_async_raise_exception_when_no_content(
         self,
diff --git a/tests/api_keys_test.py b/tests/api_keys_test.py
index f9e1e42..2d5805f 100644
--- a/tests/api_keys_test.py
+++ b/tests/api_keys_test.py
@@ -37,8 +37,8 @@ def test_api_keys_list(self) -> None:
                     {
                         "id": "91f3200a-df72-4654-b0cd-f202395f5354",
                         "name": "Production",
-                        "created_at": "2023-04-08T00:11:13.110779+00:00",
-                        "last_used_at": "2023-04-08T12:00:00.000000+00:00",
+                        "created_at": "2023-04-08 00:11:13.110779+00",
+                        "last_used_at": "2023-04-08 12:00:00+00",
                     }
                 ],
             }
@@ -50,8 +50,8 @@ def test_api_keys_list(self) -> None:
         for key in keys["data"]:
             assert key["id"] == "91f3200a-df72-4654-b0cd-f202395f5354"
             assert key["name"] == "Production"
-            assert key["created_at"] == "2023-04-08T00:11:13.110779+00:00"
-            assert key["last_used_at"] == "2023-04-08T12:00:00.000000+00:00"
+            assert key["created_at"] == "2023-04-08 00:11:13.110779+00"
+            assert key["last_used_at"] == "2023-04-08 12:00:00+00"
 
     def test_api_keys_list_last_used_at_none(self) -> None:
         self.set_mock_json(
@@ -62,7 +62,7 @@ def test_api_keys_list_last_used_at_none(self) -> None:
                     {
                         "id": "91f3200a-df72-4654-b0cd-f202395f5354",
                         "name": "Production",
-                        "created_at": "2023-04-08T00:11:13.110779+00:00",
+                        "created_at": "2023-04-08 00:11:13.110779+00",
                         "last_used_at": None,
                     }
                 ],
@@ -86,12 +86,12 @@ def test_api_keys_list_with_pagination_params(self) -> None:
                     {
                         "id": "test-key-1",
                         "name": "Test Key 1",
-                        "created_at": "2023-04-08T00:11:13.110779+00:00",
+                        "created_at": "2023-04-08 00:11:13.110779+00",
                     },
                     {
                         "id": "test-key-2",
                         "name": "Test Key 2",
-                        "created_at": "2023-04-09T00:11:13.110779+00:00",
+                        "created_at": "2023-04-09 00:11:13.110779+00",
                     },
                 ],
             }
@@ -114,7 +114,7 @@ def test_api_keys_list_with_before_param(self) -> None:
                     {
                         "id": "test-key-3",
                         "name": "Test Key 3",
-                        "created_at": "2023-04-07T00:11:13.110779+00:00",
+                        "created_at": "2023-04-07 00:11:13.110779+00",
                     }
                 ],
             }
diff --git a/tests/async_response_headers_test.py b/tests/async_response_headers_test.py
index e83f19a..26d6005 100644
--- a/tests/async_response_headers_test.py
+++ b/tests/async_response_headers_test.py
@@ -87,7 +87,7 @@ async def test_received_email_async_headers_not_overwritten_by_http_headers(
         mock_client.request.return_value = (
             b'{"id": "email_456", "object": "received_email", '
             b'"from": "sender@example.com", "to": ["recipient@example.com"], '
-            b'"subject": "Hello", "created_at": "2024-01-01T00:00:00Z", '
+            b'"subject": "Hello", "created_at": "2024-01-01 00:00:00+00", '
             b'"message_id": "msg_123", "attachments": [], '
             b'"headers": {"List-Unsubscribe": "<mailto:unsub@example.com>", '
             b'"X-Custom": "value"}}',
diff --git a/tests/attachments_async_test.py b/tests/attachments_async_test.py
index 44cf282..e539598 100644
--- a/tests/attachments_async_test.py
+++ b/tests/attachments_async_test.py
@@ -20,7 +20,7 @@ async def test_sent_email_attachments_get_async(self) -> None:
                 "content_disposition": "inline",
                 "content_id": "img001",
                 "download_url": "https://cdn.resend.com/emails/test/attachments/test-id",
-                "expires_at": "2025-10-17T14:29:41.521Z",
+                "expires_at": "2025-10-17 14:29:41.521+00",
             }
         )
 
@@ -57,7 +57,7 @@ async def test_sent_email_attachments_list_async(self) -> None:
                         "content_disposition": "inline",
                         "size": 1024,
                         "download_url": "https://cdn.resend.com/emails/test/attachments/test-id",
-                        "expires_at": "2025-10-17T14:29:41.521Z",
+                        "expires_at": "2025-10-17 14:29:41.521+00",
                     }
                 ],
             }
diff --git a/tests/attachments_test.py b/tests/attachments_test.py
index 9f99f5b..34256f1 100644
--- a/tests/attachments_test.py
+++ b/tests/attachments_test.py
@@ -18,7 +18,7 @@ def test_receiving_get_attachment(self) -> None:
                 "content_disposition": "inline",
                 "content_id": "img001",
                 "download_url": "https://inbound-cdn.resend.com/4ef9a417-02e9-4d39-ad75-9611e0fcc33c/attachments/2a0c9ce0-3112-4728-976e-47ddcd16a318?some-params=example&signature=sig-123",
-                "expires_at": "2025-10-17T14:29:41.521Z",
+                "expires_at": "2025-10-17 14:29:41.521+00",
             }
         )
 
@@ -35,7 +35,7 @@ def test_receiving_get_attachment(self) -> None:
         assert attachment["content_disposition"] == "inline"
         assert attachment["content_id"] == "img001"
         assert "https://inbound-cdn.resend.com" in attachment["download_url"]
-        assert attachment["expires_at"] == "2025-10-17T14:29:41.521Z"
+        assert attachment["expires_at"] == "2025-10-17 14:29:41.521+00"
 
     def test_receiving_get_attachment_without_content_id(self) -> None:
         self.set_mock_json(
@@ -46,7 +46,7 @@ def test_receiving_get_attachment_without_content_id(self) -> None:
                 "content_type": "application/pdf",
                 "content_disposition": "attachment",
                 "download_url": "https://inbound-cdn.resend.com/test-email/attachments/test-attachment",
-                "expires_at": "2025-10-18T10:00:00.000Z",
+                "expires_at": "2025-10-18 10:00:00+00",
             }
         )
 
@@ -87,7 +87,7 @@ def test_receiving_list_attachments(self) -> None:
                         "content_id": "img001",
                         "size": 1024,
                         "download_url": "https://inbound-cdn.resend.com/test/attachments/2a0c9ce0?signature=sig-123",
-                        "expires_at": "2025-10-17T14:29:41.521Z",
+                        "expires_at": "2025-10-17 14:29:41.521+00",
                     },
                     {
                         "id": "3b1d0df1-4223-5839-a87f-58eecd27b429",
@@ -96,7 +96,7 @@ def test_receiving_list_attachments(self) -> None:
                         "content_disposition": "attachment",
                         "size": 2048,
                         "download_url": "https://inbound-cdn.resend.com/test/attachments/3b1d0df1?signature=sig-456",
-                        "expires_at": "2025-10-17T14:29:41.521Z",
+                        "expires_at": "2025-10-17 14:29:41.521+00",
                     },
                 ],
             }
@@ -115,7 +115,7 @@ def test_receiving_list_attachments(self) -> None:
         assert attachments["data"][0]["filename"] == "avatar.png"
         assert attachments["data"][0]["size"] == 1024
         assert "https://inbound-cdn.resend.com" in attachments["data"][0]["download_url"]
-        assert attachments["data"][0]["expires_at"] == "2025-10-17T14:29:41.521Z"
+        assert attachments["data"][0]["expires_at"] == "2025-10-17 14:29:41.521+00"
         assert attachments["data"][1]["id"] == "3b1d0df1-4223-5839-a87f-58eecd27b429"
         assert attachments["data"][1]["filename"] == "document.pdf"
 
@@ -132,7 +132,7 @@ def test_receiving_list_attachments_with_pagination(self) -> None:
                         "content_disposition": "inline",
                         "size": 1024,
                         "download_url": "https://inbound-cdn.resend.com/test/attachments/2a0c9ce0?signature=sig-123",
-                        "expires_at": "2025-10-17T14:29:41.521Z",
+                        "expires_at": "2025-10-17 14:29:41.521+00",
                     },
                 ],
             }
diff --git a/tests/audiences_async_test.py b/tests/audiences_async_test.py
index bbbb8a9..d37b1d4 100644
--- a/tests/audiences_async_test.py
+++ b/tests/audiences_async_test.py
@@ -42,7 +42,7 @@ async def test_segments_get_async(self) -> None:
                 "object": "audience",
                 "id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                 "name": "Registered Users",
-                "created_at": "2023-10-06T22:59:55.977Z",
+                "created_at": "2023-10-06 22:59:55.977+00",
             }
         )
 
@@ -51,7 +51,7 @@ async def test_segments_get_async(self) -> None:
         )
         assert segment["id"] == "78261eea-8f8b-4381-83c6-79fa7120f1cf"
         assert segment["name"] == "Registered Users"
-        assert segment["created_at"] == "2023-10-06T22:59:55.977Z"
+        assert segment["created_at"] == "2023-10-06 22:59:55.977+00"
 
     async def test_should_get_segments_async_raise_exception_when_no_content(
         self,
@@ -94,7 +94,7 @@ async def test_segments_list_async(self) -> None:
                     {
                         "id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "name": "Registered Users",
-                        "created_at": "2023-10-06T22:59:55.977Z",
+                        "created_at": "2023-10-06 22:59:55.977+00",
                     }
                 ],
             }
@@ -147,7 +147,7 @@ async def test_audiences_get_async(self) -> None:
                 "object": "audience",
                 "id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                 "name": "Registered Users",
-                "created_at": "2023-10-06T22:59:55.977Z",
+                "created_at": "2023-10-06 22:59:55.977+00",
             }
         )
 
@@ -157,7 +157,7 @@ async def test_audiences_get_async(self) -> None:
             )
         assert audience["id"] == "78261eea-8f8b-4381-83c6-79fa7120f1cf"
         assert audience["name"] == "Registered Users"
-        assert audience["created_at"] == "2023-10-06T22:59:55.977Z"
+        assert audience["created_at"] == "2023-10-06 22:59:55.977+00"
 
     async def test_audiences_get_async_raises_when_no_content(
         self,
@@ -207,7 +207,7 @@ async def test_audiences_list_async(self) -> None:
                     {
                         "id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "name": "Registered Users",
-                        "created_at": "2023-10-06T22:59:55.977Z",
+                        "created_at": "2023-10-06 22:59:55.977+00",
                     }
                 ],
             }
diff --git a/tests/audiences_test.py b/tests/audiences_test.py
index d05a355..2a964e4 100644
--- a/tests/audiences_test.py
+++ b/tests/audiences_test.py
@@ -36,14 +36,14 @@ def test_audiences_get(self) -> None:
                 "object": "audience",
                 "id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                 "name": "Registered Users",
-                "created_at": "2023-10-06T22:59:55.977Z",
+                "created_at": "2023-10-06 22:59:55.977+00",
             }
         )
 
         audience = resend.Audiences.get(id="78261eea-8f8b-4381-83c6-79fa7120f1cf")
         assert audience["id"] == "78261eea-8f8b-4381-83c6-79fa7120f1cf"
         assert audience["name"] == "Registered Users"
-        assert audience["created_at"] == "2023-10-06T22:59:55.977Z"
+        assert audience["created_at"] == "2023-10-06 22:59:55.977+00"
 
     def test_should_get_audiences_raise_exception_when_no_content(self) -> None:
         self.set_mock_json(None)
@@ -80,7 +80,7 @@ def test_audiences_list(self) -> None:
                     {
                         "id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "name": "Registered Users",
-                        "created_at": "2023-10-06T22:59:55.977Z",
+                        "created_at": "2023-10-06 22:59:55.977+00",
                     }
                 ],
             }
@@ -106,12 +106,12 @@ def test_audiences_list_with_pagination_params(self) -> None:
                     {
                         "id": "audience-1",
                         "name": "First Audience",
-                        "created_at": "2023-10-06T22:59:55.977Z",
+                        "created_at": "2023-10-06 22:59:55.977+00",
                     },
                     {
                         "id": "audience-2",
                         "name": "Second Audience",
-                        "created_at": "2023-10-07T22:59:55.977Z",
+                        "created_at": "2023-10-07 22:59:55.977+00",
                     },
                 ],
             }
@@ -137,7 +137,7 @@ def test_audiences_list_with_before_param(self) -> None:
                     {
                         "id": "audience-3",
                         "name": "Third Audience",
-                        "created_at": "2023-10-05T22:59:55.977Z",
+                        "created_at": "2023-10-05 22:59:55.977+00",
                     }
                 ],
             }
diff --git a/tests/automations_async_test.py b/tests/automations_async_test.py
index 7b8cfda..6dbe0bc 100644
--- a/tests/automations_async_test.py
+++ b/tests/automations_async_test.py
@@ -56,8 +56,8 @@ async def test_automations_get_async(self) -> None:
                 "id": "b6d24b8e-af0b-4c3c-be0c-359bbd97381e",
                 "name": "Welcome Sequence",
                 "status": "enabled",
-                "created_at": "2024-01-01T00:00:00.000Z",
-                "updated_at": "2024-01-02T00:00:00.000Z",
+                "created_at": "2024-01-01 00:00:00+00",
+                "updated_at": "2024-01-02 00:00:00+00",
                 "steps": [],
                 "connections": [],
             }
@@ -155,8 +155,8 @@ async def test_automations_list_async(self) -> None:
                         "id": "b6d24b8e-af0b-4c3c-be0c-359bbd97381e",
                         "name": "Welcome Sequence",
                         "status": "enabled",
-                        "created_at": "2024-01-01T00:00:00.000Z",
-                        "updated_at": "2024-01-02T00:00:00.000Z",
+                        "created_at": "2024-01-01 00:00:00+00",
+                        "updated_at": "2024-01-02 00:00:00+00",
                     },
                 ],
             }
@@ -182,9 +182,9 @@ async def test_automations_list_runs_async(self) -> None:
                     {
                         "id": "run_123",
                         "status": "completed",
-                        "started_at": "2024-01-01T10:00:00.000Z",
-                        "completed_at": "2024-01-01T10:05:00.000Z",
-                        "created_at": "2024-01-01T09:59:00.000Z",
+                        "started_at": "2024-01-01 10:00:00+00",
+                        "completed_at": "2024-01-01 10:05:00+00",
+                        "created_at": "2024-01-01 09:59:00+00",
                     },
                 ],
             }
@@ -211,9 +211,9 @@ async def test_automations_get_run_async(self) -> None:
                 "object": "automation_run",
                 "id": "run_123",
                 "status": "completed",
-                "started_at": "2024-01-01T10:00:00.000Z",
-                "completed_at": "2024-01-01T10:05:00.000Z",
-                "created_at": "2024-01-01T09:59:00.000Z",
+                "started_at": "2024-01-01 10:00:00+00",
+                "completed_at": "2024-01-01 10:05:00+00",
+                "created_at": "2024-01-01 09:59:00+00",
                 "steps": [],
             }
         )
diff --git a/tests/automations_test.py b/tests/automations_test.py
index 9f09243..020f1c6 100644
--- a/tests/automations_test.py
+++ b/tests/automations_test.py
@@ -65,8 +65,8 @@ def test_automations_get(self) -> None:
                 "id": "b6d24b8e-af0b-4c3c-be0c-359bbd97381e",
                 "name": "Welcome Sequence",
                 "status": "enabled",
-                "created_at": "2024-01-01T00:00:00.000Z",
-                "updated_at": "2024-01-02T00:00:00.000Z",
+                "created_at": "2024-01-01 00:00:00+00",
+                "updated_at": "2024-01-02 00:00:00+00",
                 "steps": [
                     {
                         "key": "trigger_1",
@@ -83,8 +83,8 @@ def test_automations_get(self) -> None:
         assert automation["id"] == "b6d24b8e-af0b-4c3c-be0c-359bbd97381e"
         assert automation["name"] == "Welcome Sequence"
         assert automation["status"] == "enabled"
-        assert automation["created_at"] == "2024-01-01T00:00:00.000Z"
-        assert automation["updated_at"] == "2024-01-02T00:00:00.000Z"
+        assert automation["created_at"] == "2024-01-01 00:00:00+00"
+        assert automation["updated_at"] == "2024-01-02 00:00:00+00"
         assert len(automation["steps"]) == 1
         assert automation["steps"][0]["key"] == "trigger_1"
         assert automation["steps"][0]["type"] == "trigger"
@@ -159,15 +159,15 @@ def test_automations_list(self) -> None:
                         "id": "b6d24b8e-af0b-4c3c-be0c-359bbd97381e",
                         "name": "Welcome Sequence",
                         "status": "enabled",
-                        "created_at": "2024-01-01T00:00:00.000Z",
-                        "updated_at": "2024-01-02T00:00:00.000Z",
+                        "created_at": "2024-01-01 00:00:00+00",
+                        "updated_at": "2024-01-02 00:00:00+00",
                     },
                     {
                         "id": "c7e35c9f-bf1c-5d4d-cf1d-460cce08492f",
                         "name": "Onboarding Flow",
                         "status": "disabled",
-                        "created_at": "2024-02-01T00:00:00.000Z",
-                        "updated_at": "2024-02-02T00:00:00.000Z",
+                        "created_at": "2024-02-01 00:00:00+00",
+                        "updated_at": "2024-02-02 00:00:00+00",
                     },
                 ],
             }
@@ -182,7 +182,7 @@ def test_automations_list(self) -> None:
         assert first["id"] == "b6d24b8e-af0b-4c3c-be0c-359bbd97381e"
         assert first["name"] == "Welcome Sequence"
         assert first["status"] == "enabled"
-        assert first["created_at"] == "2024-01-01T00:00:00.000Z"
+        assert first["created_at"] == "2024-01-01 00:00:00+00"
 
         second = automations["data"][1]
         assert second["id"] == "c7e35c9f-bf1c-5d4d-cf1d-460cce08492f"
@@ -198,8 +198,8 @@ def test_automations_list_with_status_filter(self) -> None:
                         "id": "b6d24b8e-af0b-4c3c-be0c-359bbd97381e",
                         "name": "Welcome Sequence",
                         "status": "enabled",
-                        "created_at": "2024-01-01T00:00:00.000Z",
-                        "updated_at": "2024-01-02T00:00:00.000Z",
+                        "created_at": "2024-01-01 00:00:00+00",
+                        "updated_at": "2024-01-02 00:00:00+00",
                     },
                 ],
             }
@@ -221,8 +221,8 @@ def test_automations_list_with_pagination_params(self) -> None:
                         "id": "b6d24b8e-af0b-4c3c-be0c-359bbd97381e",
                         "name": "Welcome Sequence",
                         "status": "enabled",
-                        "created_at": "2024-01-01T00:00:00.000Z",
-                        "updated_at": "2024-01-02T00:00:00.000Z",
+                        "created_at": "2024-01-01 00:00:00+00",
+                        "updated_at": "2024-01-02 00:00:00+00",
                     },
                 ],
             }
@@ -245,16 +245,16 @@ def test_automations_list_runs(self) -> None:
                     {
                         "id": "run_123",
                         "status": "completed",
-                        "started_at": "2024-01-01T10:00:00.000Z",
-                        "completed_at": "2024-01-01T10:05:00.000Z",
-                        "created_at": "2024-01-01T09:59:00.000Z",
+                        "started_at": "2024-01-01 10:00:00+00",
+                        "completed_at": "2024-01-01 10:05:00+00",
+                        "created_at": "2024-01-01 09:59:00+00",
                     },
                     {
                         "id": "run_456",
                         "status": "running",
-                        "started_at": "2024-01-02T10:00:00.000Z",
+                        "started_at": "2024-01-02 10:00:00+00",
                         "completed_at": None,
-                        "created_at": "2024-01-02T09:59:00.000Z",
+                        "created_at": "2024-01-02 09:59:00+00",
                     },
                 ],
             }
@@ -268,8 +268,8 @@ def test_automations_list_runs(self) -> None:
         first = runs["data"][0]
         assert first["id"] == "run_123"
         assert first["status"] == "completed"
-        assert first["started_at"] == "2024-01-01T10:00:00.000Z"
-        assert first["completed_at"] == "2024-01-01T10:05:00.000Z"
+        assert first["started_at"] == "2024-01-01 10:00:00+00"
+        assert first["completed_at"] == "2024-01-01 10:05:00+00"
 
         second = runs["data"][1]
         assert second["id"] == "run_456"
@@ -285,9 +285,9 @@ def test_automations_list_runs_with_status_filter(self) -> None:
                     {
                         "id": "run_123",
                         "status": "completed",
-                        "started_at": "2024-01-01T10:00:00.000Z",
-                        "completed_at": "2024-01-01T10:05:00.000Z",
-                        "created_at": "2024-01-01T09:59:00.000Z",
+                        "started_at": "2024-01-01 10:00:00+00",
+                        "completed_at": "2024-01-01 10:05:00+00",
+                        "created_at": "2024-01-01 09:59:00+00",
                     },
                 ],
             }
@@ -306,29 +306,29 @@ def test_automations_get_run(self) -> None:
                 "object": "automation_run",
                 "id": "run_123",
                 "status": "completed",
-                "started_at": "2024-01-01T10:00:00.000Z",
-                "completed_at": "2024-01-01T10:05:00.000Z",
-                "created_at": "2024-01-01T09:59:00.000Z",
+                "started_at": "2024-01-01 10:00:00+00",
+                "completed_at": "2024-01-01 10:05:00+00",
+                "created_at": "2024-01-01 09:59:00+00",
                 "steps": [
                     {
                         "key": "trigger_1",
                         "type": "trigger",
                         "status": "completed",
-                        "started_at": "2024-01-01T10:00:00.000Z",
-                        "completed_at": "2024-01-01T10:00:01.000Z",
+                        "started_at": "2024-01-01 10:00:00+00",
+                        "completed_at": "2024-01-01 10:00:01+00",
                         "output": None,
                         "error": None,
-                        "created_at": "2024-01-01T09:59:00.000Z",
+                        "created_at": "2024-01-01 09:59:00+00",
                     },
                     {
                         "key": "email_1",
                         "type": "send_email",
                         "status": "completed",
-                        "started_at": "2024-01-01T10:01:00.000Z",
-                        "completed_at": "2024-01-01T10:01:02.000Z",
+                        "started_at": "2024-01-01 10:01:00+00",
+                        "completed_at": "2024-01-01 10:01:02+00",
                         "output": None,
                         "error": None,
-                        "created_at": "2024-01-01T09:59:00.000Z",
+                        "created_at": "2024-01-01 09:59:00+00",
                     },
                 ],
             }
@@ -340,8 +340,8 @@ def test_automations_get_run(self) -> None:
         assert run["object"] == "automation_run"
         assert run["id"] == "run_123"
         assert run["status"] == "completed"
-        assert run["started_at"] == "2024-01-01T10:00:00.000Z"
-        assert run["completed_at"] == "2024-01-01T10:05:00.000Z"
+        assert run["started_at"] == "2024-01-01 10:00:00+00"
+        assert run["completed_at"] == "2024-01-01 10:05:00+00"
         assert len(run["steps"]) == 2
         assert run["steps"][0]["key"] == "trigger_1"
         assert run["steps"][0]["type"] == "trigger"
diff --git a/tests/broadcasts_async_test.py b/tests/broadcasts_async_test.py
index c1e6f23..1f4a759 100644
--- a/tests/broadcasts_async_test.py
+++ b/tests/broadcasts_async_test.py
@@ -76,7 +76,7 @@ async def test_broadcasts_get_async(self) -> None:
                 "reply_to": None,
                 "preview_text": "Check out our latest announcements",
                 "status": "draft",
-                "created_at": "2024-12-01T19:32:22.980Z",
+                "created_at": "2024-12-01 19:32:22.98+00",
                 "scheduled_at": None,
                 "sent_at": None,
             }
@@ -93,7 +93,7 @@ async def test_broadcasts_get_async(self) -> None:
         assert broadcast["reply_to"] is None
         assert broadcast["preview_text"] == "Check out our latest announcements"
         assert broadcast["status"] == "draft"
-        assert broadcast["created_at"] == "2024-12-01T19:32:22.980Z"
+        assert broadcast["created_at"] == "2024-12-01 19:32:22.98+00"
         assert broadcast["scheduled_at"] is None
         assert broadcast["sent_at"] is None
 
@@ -158,7 +158,7 @@ async def test_broadcasts_list_async(self) -> None:
                         "id": "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794",
                         "audience_id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "status": "draft",
-                        "created_at": "2024-11-01T15:13:31.723Z",
+                        "created_at": "2024-11-01 15:13:31.723+00",
                         "scheduled_at": None,
                         "sent_at": None,
                     },
@@ -166,9 +166,9 @@ async def test_broadcasts_list_async(self) -> None:
                         "id": "559ac32e-9ef5-46fb-82a1-b76b840c0f7b",
                         "audience_id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "status": "sent",
-                        "created_at": "2024-12-01T19:32:22.980Z",
-                        "scheduled_at": "2024-12-02T19:32:22.980Z",
-                        "sent_at": "2024-12-02T19:32:22.980Z",
+                        "created_at": "2024-12-01 19:32:22.98+00",
+                        "scheduled_at": "2024-12-02 19:32:22.98+00",
+                        "sent_at": "2024-12-02 19:32:22.98+00",
                     },
                 ],
             }
@@ -184,7 +184,7 @@ async def test_broadcasts_list_async(self) -> None:
         assert broadcast["id"] == "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794"
         assert broadcast["audience_id"] == "78261eea-8f8b-4381-83c6-79fa7120f1cf"
         assert broadcast["status"] == "draft"
-        assert broadcast["created_at"] == "2024-11-01T15:13:31.723Z"
+        assert broadcast["created_at"] == "2024-11-01 15:13:31.723+00"
         assert broadcast["scheduled_at"] is None
         assert broadcast["sent_at"] is None
 
@@ -192,9 +192,9 @@ async def test_broadcasts_list_async(self) -> None:
         assert broadcast["id"] == "559ac32e-9ef5-46fb-82a1-b76b840c0f7b"
         assert broadcast["audience_id"] == "78261eea-8f8b-4381-83c6-79fa7120f1cf"
         assert broadcast["status"] == "sent"
-        assert broadcast["created_at"] == "2024-12-01T19:32:22.980Z"
-        assert broadcast["scheduled_at"] == "2024-12-02T19:32:22.980Z"
-        assert broadcast["sent_at"] == "2024-12-02T19:32:22.980Z"
+        assert broadcast["created_at"] == "2024-12-01 19:32:22.98+00"
+        assert broadcast["scheduled_at"] == "2024-12-02 19:32:22.98+00"
+        assert broadcast["sent_at"] == "2024-12-02 19:32:22.98+00"
 
     async def test_should_list_broadcasts_async_raise_exception_when_no_content(
         self,
diff --git a/tests/broadcasts_test.py b/tests/broadcasts_test.py
index 6e2c1dd..4b1332c 100644
--- a/tests/broadcasts_test.py
+++ b/tests/broadcasts_test.py
@@ -42,7 +42,7 @@ def test_broadcasts_get(self) -> None:
                 "reply_to": None,
                 "preview_text": "Check out our latest announcements",
                 "status": "draft",
-                "created_at": "2024-12-01T19:32:22.980Z",
+                "created_at": "2024-12-01 19:32:22.98+00",
                 "scheduled_at": None,
                 "sent_at": None,
                 "html": "<p>Hello World</p>",
@@ -59,7 +59,7 @@ def test_broadcasts_get(self) -> None:
         assert broadcast["reply_to"] is None
         assert broadcast["preview_text"] == "Check out our latest announcements"
         assert broadcast["status"] == "draft"
-        assert broadcast["created_at"] == "2024-12-01T19:32:22.980Z"
+        assert broadcast["created_at"] == "2024-12-01 19:32:22.98+00"
         assert broadcast["scheduled_at"] is None
         assert broadcast["sent_at"] is None
         assert broadcast["html"] == "<p>Hello World</p>"
@@ -124,7 +124,7 @@ def test_broadcasts_list(self) -> None:
                         "id": "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794",
                         "audience_id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "status": "draft",
-                        "created_at": "2024-11-01T15:13:31.723Z",
+                        "created_at": "2024-11-01 15:13:31.723+00",
                         "scheduled_at": None,
                         "sent_at": None,
                     },
@@ -132,9 +132,9 @@ def test_broadcasts_list(self) -> None:
                         "id": "559ac32e-9ef5-46fb-82a1-b76b840c0f7b",
                         "audience_id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "status": "sent",
-                        "created_at": "2024-12-01T19:32:22.980Z",
-                        "scheduled_at": "2024-12-02T19:32:22.980Z",
-                        "sent_at": "2024-12-02T19:32:22.980Z",
+                        "created_at": "2024-12-01 19:32:22.98+00",
+                        "scheduled_at": "2024-12-02 19:32:22.98+00",
+                        "sent_at": "2024-12-02 19:32:22.98+00",
                     },
                 ],
             }
@@ -149,7 +149,7 @@ def test_broadcasts_list(self) -> None:
         assert broadcast["id"] == "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794"
         assert broadcast["audience_id"] == "78261eea-8f8b-4381-83c6-79fa7120f1cf"
         assert broadcast["status"] == "draft"
-        assert broadcast["created_at"] == "2024-11-01T15:13:31.723Z"
+        assert broadcast["created_at"] == "2024-11-01 15:13:31.723+00"
         assert broadcast["scheduled_at"] is None
         assert broadcast["sent_at"] is None
 
@@ -157,9 +157,9 @@ def test_broadcasts_list(self) -> None:
         assert broadcast["id"] == "559ac32e-9ef5-46fb-82a1-b76b840c0f7b"
         assert broadcast["audience_id"] == "78261eea-8f8b-4381-83c6-79fa7120f1cf"
         assert broadcast["status"] == "sent"
-        assert broadcast["created_at"] == "2024-12-01T19:32:22.980Z"
-        assert broadcast["scheduled_at"] == "2024-12-02T19:32:22.980Z"
-        assert broadcast["sent_at"] == "2024-12-02T19:32:22.980Z"
+        assert broadcast["created_at"] == "2024-12-01 19:32:22.98+00"
+        assert broadcast["scheduled_at"] == "2024-12-02 19:32:22.98+00"
+        assert broadcast["sent_at"] == "2024-12-02 19:32:22.98+00"
 
     def test_broadcasts_list_with_pagination_params(self) -> None:
         self.set_mock_json(
@@ -171,7 +171,7 @@ def test_broadcasts_list_with_pagination_params(self) -> None:
                         "id": "broadcast-1",
                         "audience_id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "status": "draft",
-                        "created_at": "2024-11-01T15:13:31.723Z",
+                        "created_at": "2024-11-01 15:13:31.723+00",
                         "scheduled_at": None,
                         "sent_at": None,
                     },
@@ -179,9 +179,9 @@ def test_broadcasts_list_with_pagination_params(self) -> None:
                         "id": "broadcast-2",
                         "audience_id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "status": "sent",
-                        "created_at": "2024-12-01T19:32:22.980Z",
-                        "scheduled_at": "2024-12-02T19:32:22.980Z",
-                        "sent_at": "2024-12-02T19:32:22.980Z",
+                        "created_at": "2024-12-01 19:32:22.98+00",
+                        "scheduled_at": "2024-12-02 19:32:22.98+00",
+                        "sent_at": "2024-12-02 19:32:22.98+00",
                     },
                 ],
             }
@@ -210,7 +210,7 @@ def test_broadcasts_list_with_before_param(self) -> None:
                         "id": "broadcast-3",
                         "audience_id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "status": "draft",
-                        "created_at": "2024-10-01T15:13:31.723Z",
+                        "created_at": "2024-10-01 15:13:31.723+00",
                         "scheduled_at": None,
                         "sent_at": None,
                     }
diff --git a/tests/contact_imports_test.py b/tests/contact_imports_test.py
index d502aff..3dc1d0c 100644
--- a/tests/contact_imports_test.py
+++ b/tests/contact_imports_test.py
@@ -43,7 +43,7 @@ def test_get_contact_import(self) -> None:
                 "object": "contact_import",
                 "id": "479e3145-dd38-476b-932c-529ceb705947",
                 "status": "completed",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "counts": {
                     "total": 100,
                     "created": 80,
@@ -78,7 +78,7 @@ def test_list_contact_imports(self) -> None:
                         "object": "contact_import",
                         "id": "479e3145-dd38-476b-932c-529ceb705947",
                         "status": "completed",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                     }
                 ],
             }
diff --git a/tests/contact_properties_async_test.py b/tests/contact_properties_async_test.py
index f33c4be..491defd 100644
--- a/tests/contact_properties_async_test.py
+++ b/tests/contact_properties_async_test.py
@@ -47,7 +47,7 @@ async def test_contact_properties_get_async(self) -> None:
                 "id": "prop_123456",
                 "key": "age",
                 "object": "contact_property",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "type": "number",
                 "fallback_value": 0,
             }
@@ -78,7 +78,7 @@ async def test_contact_properties_list_async(self) -> None:
                         "id": "prop_123456",
                         "key": "age",
                         "object": "contact_property",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "type": "number",
                         "fallback_value": 0,
                     }
diff --git a/tests/contact_properties_test.py b/tests/contact_properties_test.py
index 7c56c3c..fc069a4 100644
--- a/tests/contact_properties_test.py
+++ b/tests/contact_properties_test.py
@@ -47,7 +47,7 @@ def test_contact_properties_list(self) -> None:
                         "id": "prop_123456",
                         "key": "age",
                         "object": "contact_property",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "type": "number",
                         "fallback_value": 0,
                     }
@@ -82,7 +82,7 @@ def test_contact_properties_list_with_pagination(self) -> None:
                         "id": "prop_1",
                         "key": "age",
                         "object": "contact_property",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "type": "number",
                         "fallback_value": 0,
                     },
@@ -90,7 +90,7 @@ def test_contact_properties_list_with_pagination(self) -> None:
                         "id": "prop_2",
                         "key": "city",
                         "object": "contact_property",
-                        "created_at": "2023-10-07T23:47:56.678Z",
+                        "created_at": "2023-10-07 23:47:56.678+00",
                         "type": "string",
                         "fallback_value": "Unknown",
                     },
@@ -117,7 +117,7 @@ def test_contact_properties_get(self) -> None:
                 "id": "prop_123456",
                 "key": "age",
                 "object": "contact_property",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "type": "number",
                 "fallback_value": 0,
             }
diff --git a/tests/contacts_async_test.py b/tests/contacts_async_test.py
index d503935..ff140d8 100644
--- a/tests/contacts_async_test.py
+++ b/tests/contacts_async_test.py
@@ -110,7 +110,7 @@ async def test_contacts_get_async(self) -> None:
                 "email": "steve.wozniak@gmail.com",
                 "first_name": "Steve",
                 "last_name": "Wozniak",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "unsubscribed": False,
             }
         )
@@ -123,7 +123,7 @@ async def test_contacts_get_async(self) -> None:
         assert contact["email"] == "steve.wozniak@gmail.com"
         assert contact["first_name"] == "Steve"
         assert contact["last_name"] == "Wozniak"
-        assert contact["created_at"] == "2023-10-06T23:47:56.678Z"
+        assert contact["created_at"] == "2023-10-06 23:47:56.678+00"
         assert contact["unsubscribed"] is False
 
     async def test_contacts_get_async_by_email(self) -> None:
@@ -134,7 +134,7 @@ async def test_contacts_get_async_by_email(self) -> None:
                 "email": "steve@woz.com",
                 "first_name": "Steve",
                 "last_name": "Wozniak",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "unsubscribed": False,
             }
         )
@@ -147,7 +147,7 @@ async def test_contacts_get_async_by_email(self) -> None:
         assert contact["email"] == "steve@woz.com"
         assert contact["first_name"] == "Steve"
         assert contact["last_name"] == "Wozniak"
-        assert contact["created_at"] == "2023-10-06T23:47:56.678Z"
+        assert contact["created_at"] == "2023-10-06 23:47:56.678+00"
         assert contact["unsubscribed"] is False
 
     async def test_contacts_get_async_encodes_email_identifier(self) -> None:
@@ -156,7 +156,7 @@ async def test_contacts_get_async_encodes_email_identifier(self) -> None:
                 "object": "contact",
                 "id": "e169aa45-1ecf-4183-9955-b1499d5701d3",
                 "email": "team/a?b@example.com",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "unsubscribed": False,
             }
         )
@@ -276,7 +276,7 @@ async def test_contacts_list_async(self) -> None:
                         "email": "steve.wozniak@gmail.com",
                         "first_name": "Steve",
                         "last_name": "Wozniak",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "unsubscribed": False,
                     }
                 ],
@@ -290,7 +290,7 @@ async def test_contacts_list_async(self) -> None:
         assert contacts["data"][0]["email"] == "steve.wozniak@gmail.com"
         assert contacts["data"][0]["first_name"] == "Steve"
         assert contacts["data"][0]["last_name"] == "Wozniak"
-        assert contacts["data"][0]["created_at"] == "2023-10-06T23:47:56.678Z"
+        assert contacts["data"][0]["created_at"] == "2023-10-06 23:47:56.678+00"
         assert contacts["data"][0]["unsubscribed"] is False
 
     async def test_should_list_contacts_async_raise_exception_when_no_content(
@@ -313,7 +313,7 @@ async def test_contacts_list_async_by_segment_id(self) -> None:
                         "email": "steve.wozniak@gmail.com",
                         "first_name": "Steve",
                         "last_name": "Wozniak",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "unsubscribed": False,
                     }
                 ],
diff --git a/tests/contacts_segments_async_test.py b/tests/contacts_segments_async_test.py
index 7482156..7498e22 100644
--- a/tests/contacts_segments_async_test.py
+++ b/tests/contacts_segments_async_test.py
@@ -118,12 +118,12 @@ async def test_contact_segments_list_async(self) -> None:
                     {
                         "id": "segment-1",
                         "name": "Segment 1",
-                        "created_at": "2023-10-06T22:59:55.977Z",
+                        "created_at": "2023-10-06 22:59:55.977+00",
                     },
                     {
                         "id": "segment-2",
                         "name": "Segment 2",
-                        "created_at": "2023-10-07T22:59:55.977Z",
+                        "created_at": "2023-10-07 22:59:55.977+00",
                     },
                 ],
             }
diff --git a/tests/contacts_segments_test.py b/tests/contacts_segments_test.py
index a103d3a..290f167 100644
--- a/tests/contacts_segments_test.py
+++ b/tests/contacts_segments_test.py
@@ -101,12 +101,12 @@ def test_contact_segments_list(self) -> None:
                     {
                         "id": "segment-1",
                         "name": "Segment 1",
-                        "created_at": "2023-10-06T22:59:55.977Z",
+                        "created_at": "2023-10-06 22:59:55.977+00",
                     },
                     {
                         "id": "segment-2",
                         "name": "Segment 2",
-                        "created_at": "2023-10-07T22:59:55.977Z",
+                        "created_at": "2023-10-07 22:59:55.977+00",
                     },
                 ],
             }
@@ -133,7 +133,7 @@ def test_contact_segments_list_with_email(self) -> None:
                     {
                         "id": "segment-3",
                         "name": "Segment 3",
-                        "created_at": "2023-10-08T22:59:55.977Z",
+                        "created_at": "2023-10-08 22:59:55.977+00",
                     }
                 ],
             }
@@ -176,7 +176,7 @@ def test_contact_segments_list_with_pagination(self) -> None:
                     {
                         "id": "segment-4",
                         "name": "Segment 4",
-                        "created_at": "2023-10-09T22:59:55.977Z",
+                        "created_at": "2023-10-09 22:59:55.977+00",
                     }
                 ],
             }
diff --git a/tests/contacts_test.py b/tests/contacts_test.py
index ebb1f49..49841fc 100644
--- a/tests/contacts_test.py
+++ b/tests/contacts_test.py
@@ -82,7 +82,7 @@ def test_contacts_get(self) -> None:
                 "email": "steve.wozniak@gmail.com",
                 "first_name": "Steve",
                 "last_name": "Wozniak",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "unsubscribed": False,
             }
         )
@@ -95,7 +95,7 @@ def test_contacts_get(self) -> None:
         assert contact["email"] == "steve.wozniak@gmail.com"
         assert contact.get("first_name") == "Steve"
         assert contact.get("last_name") == "Wozniak"
-        assert contact["created_at"] == "2023-10-06T23:47:56.678Z"
+        assert contact["created_at"] == "2023-10-06 23:47:56.678+00"
         assert contact["unsubscribed"] is False
 
     def test_contacts_get_by_email(self) -> None:
@@ -106,7 +106,7 @@ def test_contacts_get_by_email(self) -> None:
                 "email": "steve@woz.com",
                 "first_name": "Steve",
                 "last_name": "Wozniak",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "unsubscribed": False,
             }
         )
@@ -119,7 +119,7 @@ def test_contacts_get_by_email(self) -> None:
         assert contact["email"] == "steve@woz.com"
         assert contact["first_name"] == "Steve"
         assert contact["last_name"] == "Wozniak"
-        assert contact["created_at"] == "2023-10-06T23:47:56.678Z"
+        assert contact["created_at"] == "2023-10-06 23:47:56.678+00"
         assert contact["unsubscribed"] is False
 
     def test_contacts_get_encodes_email_identifier(self) -> None:
@@ -128,7 +128,7 @@ def test_contacts_get_encodes_email_identifier(self) -> None:
                 "object": "contact",
                 "id": "e169aa45-1ecf-4183-9955-b1499d5701d3",
                 "email": "team/a?b@example.com",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "unsubscribed": False,
             }
         )
@@ -229,7 +229,7 @@ def test_contacts_list(self) -> None:
                         "email": "steve.wozniak@gmail.com",
                         "first_name": "Steve",
                         "last_name": "Wozniak",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "unsubscribed": False,
                     }
                 ],
@@ -245,7 +245,7 @@ def test_contacts_list(self) -> None:
         assert contacts["data"][0]["email"] == "steve.wozniak@gmail.com"
         assert contacts["data"][0].get("first_name") == "Steve"
         assert contacts["data"][0].get("last_name") == "Wozniak"
-        assert contacts["data"][0]["created_at"] == "2023-10-06T23:47:56.678Z"
+        assert contacts["data"][0]["created_at"] == "2023-10-06 23:47:56.678+00"
         assert contacts["data"][0]["unsubscribed"] is False
 
     def test_should_list_contacts_raise_exception_when_no_content(self) -> None:
@@ -264,7 +264,7 @@ def test_contacts_list_with_pagination_params(self) -> None:
                         "email": "contact1@example.com",
                         "first_name": "Contact",
                         "last_name": "One",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "unsubscribed": False,
                     },
                     {
@@ -272,7 +272,7 @@ def test_contacts_list_with_pagination_params(self) -> None:
                         "email": "contact2@example.com",
                         "first_name": "Contact",
                         "last_name": "Two",
-                        "created_at": "2023-10-07T23:47:56.678Z",
+                        "created_at": "2023-10-07 23:47:56.678+00",
                         "unsubscribed": False,
                     },
                 ],
@@ -303,7 +303,7 @@ def test_contacts_list_with_before_param(self) -> None:
                         "email": "contact3@example.com",
                         "first_name": "Contact",
                         "last_name": "Three",
-                        "created_at": "2023-10-05T23:47:56.678Z",
+                        "created_at": "2023-10-05 23:47:56.678+00",
                         "unsubscribed": False,
                     }
                 ],
@@ -375,7 +375,7 @@ def test_contacts_get_global(self) -> None:
                 "email": "global@example.com",
                 "first_name": "Global",
                 "last_name": "Contact",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
                 "unsubscribed": False,
                 "properties": {"tier": "premium"},
             }
@@ -397,7 +397,7 @@ def test_contacts_list_global(self) -> None:
                         "email": "global1@example.com",
                         "first_name": "Global",
                         "last_name": "One",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "unsubscribed": False,
                         "properties": {"tier": "free"},
                     },
@@ -406,7 +406,7 @@ def test_contacts_list_global(self) -> None:
                         "email": "global2@example.com",
                         "first_name": "Global",
                         "last_name": "Two",
-                        "created_at": "2023-10-07T23:47:56.678Z",
+                        "created_at": "2023-10-07 23:47:56.678+00",
                         "unsubscribed": False,
                         "properties": {"tier": "premium"},
                     },
@@ -432,7 +432,7 @@ def test_contacts_list_by_segment_id(self) -> None:
                         "email": "steve.wozniak@gmail.com",
                         "first_name": "Steve",
                         "last_name": "Wozniak",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "unsubscribed": False,
                     }
                 ],
@@ -458,7 +458,7 @@ def test_contacts_list_by_segment_id_with_pagination(self) -> None:
                         "email": "contact1@example.com",
                         "first_name": "Contact",
                         "last_name": "One",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                         "unsubscribed": False,
                     }
                 ],
diff --git a/tests/domain_claims_async_test.py b/tests/domain_claims_async_test.py
index 25f60a2..0f72957 100644
--- a/tests/domain_claims_async_test.py
+++ b/tests/domain_claims_async_test.py
@@ -27,8 +27,8 @@ async def test_domain_claims_create_async(self) -> None:
                 },
                 "blocked_reason": None,
                 "failure_reason": None,
-                "created_at": "2026-06-16T17:12:02.059593+00:00",
-                "expires_at": "2026-06-23T17:12:02.059593+00:00",
+                "created_at": "2026-06-16 17:12:02.059593+00",
+                "expires_at": "2026-06-23 17:12:02.059593+00",
             }
         )
 
@@ -81,8 +81,8 @@ async def test_domain_claims_get_async(self) -> None:
                 "region": "us-east-1",
                 "blocked_reason": "grace_period",
                 "failure_reason": None,
-                "created_at": "2026-06-16T17:12:02.059593+00:00",
-                "expires_at": "2026-06-23T17:12:02.059593+00:00",
+                "created_at": "2026-06-16 17:12:02.059593+00",
+                "expires_at": "2026-06-23 17:12:02.059593+00",
             }
         )
 
diff --git a/tests/domain_claims_test.py b/tests/domain_claims_test.py
index 0a4d1a5..1ac3b0b 100644
--- a/tests/domain_claims_test.py
+++ b/tests/domain_claims_test.py
@@ -23,8 +23,8 @@ def test_domain_claims_create(self) -> None:
                 },
                 "blocked_reason": None,
                 "failure_reason": None,
-                "created_at": "2026-06-16T17:12:02.059593+00:00",
-                "expires_at": "2026-06-23T17:12:02.059593+00:00",
+                "created_at": "2026-06-16 17:12:02.059593+00",
+                "expires_at": "2026-06-23 17:12:02.059593+00",
             }
         )
 
@@ -84,8 +84,8 @@ def test_domain_claims_get(self) -> None:
                 "region": "us-east-1",
                 "blocked_reason": "grace_period",
                 "failure_reason": None,
-                "created_at": "2026-06-16T17:12:02.059593+00:00",
-                "expires_at": "2026-06-23T17:12:02.059593+00:00",
+                "created_at": "2026-06-16 17:12:02.059593+00",
+                "expires_at": "2026-06-23 17:12:02.059593+00",
             }
         )
 
diff --git a/tests/domains_async_test.py b/tests/domains_async_test.py
index 2db4ac4..c9f900b 100644
--- a/tests/domains_async_test.py
+++ b/tests/domains_async_test.py
@@ -15,7 +15,7 @@ async def test_domains_create_async(self) -> None:
             {
                 "id": "4dd369bc-aa82-4ff3-97de-514ae3000ee0",
                 "name": "example.com",
-                "created_at": "2023-03-28T17:12:02.059593+00:00",
+                "created_at": "2023-03-28 17:12:02.059593+00",
                 "status": "not_started",
                 "records": [
                     {
@@ -73,7 +73,7 @@ async def test_domains_create_async(self) -> None:
         assert domain["id"] == "4dd369bc-aa82-4ff3-97de-514ae3000ee0"
         assert domain["name"] == "example.com"
         assert domain["status"] == "not_started"
-        assert domain["created_at"] == "2023-03-28T17:12:02.059593+00:00"
+        assert domain["created_at"] == "2023-03-28 17:12:02.059593+00"
         assert domain["region"] == "us-east-1"
 
     async def test_should_create_domains_async_raise_exception_when_no_content(
@@ -93,7 +93,7 @@ async def test_domains_get_async(self) -> None:
                 "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
                 "name": "example.com",
                 "status": "not_started",
-                "created_at": "2023-04-26T20:21:26.347412+00:00",
+                "created_at": "2023-04-26 20:21:26.347412+00",
                 "region": "us-east-1",
             }
         )
@@ -104,7 +104,7 @@ async def test_domains_get_async(self) -> None:
         assert domain["id"] == "d91cd9bd-1176-453e-8fc1-35364d380206"
         assert domain["name"] == "example.com"
         assert domain["status"] == "not_started"
-        assert domain["created_at"] == "2023-04-26T20:21:26.347412+00:00"
+        assert domain["created_at"] == "2023-04-26 20:21:26.347412+00"
         assert domain["region"] == "us-east-1"
 
     async def test_should_get_domains_async_raise_exception_when_no_content(
@@ -124,7 +124,7 @@ async def test_domains_list_async(self) -> None:
                         "id": "4dd369bc-aa82-4ff3-97de-514ae3000ee0",
                         "name": "example.com",
                         "status": "not_started",
-                        "created_at": "2023-03-28T17:12:02.059593+00:00",
+                        "created_at": "2023-03-28 17:12:02.059593+00",
                         "region": "us-east-1",
                     }
                 ]
@@ -136,7 +136,7 @@ async def test_domains_list_async(self) -> None:
             assert domain["id"] == "4dd369bc-aa82-4ff3-97de-514ae3000ee0"
             assert domain["name"] == "example.com"
             assert domain["status"] == "not_started"
-            assert domain["created_at"] == "2023-03-28T17:12:02.059593+00:00"
+            assert domain["created_at"] == "2023-03-28 17:12:02.059593+00"
             assert domain["region"] == "us-east-1"
 
     async def test_should_list_domains_async_raise_exception_when_no_content(
@@ -151,7 +151,7 @@ async def test_domains_create_async_with_tracking_subdomain(self) -> None:
             {
                 "id": "4dd369bc-aa82-4ff3-97de-514ae3000ee0",
                 "name": "example.com",
-                "created_at": "2023-03-28T17:12:02.059593+00:00",
+                "created_at": "2023-03-28 17:12:02.059593+00",
                 "status": "not_started",
                 "open_tracking": True,
                 "click_tracking": True,
@@ -220,7 +220,7 @@ async def test_domains_get_async_with_tracking_fields(self) -> None:
                 "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
                 "name": "example.com",
                 "status": "not_started",
-                "created_at": "2023-04-26T20:21:26.347412+00:00",
+                "created_at": "2023-04-26 20:21:26.347412+00",
                 "region": "us-east-1",
                 "open_tracking": True,
                 "click_tracking": True,
@@ -267,7 +267,7 @@ async def test_domains_update_async(self) -> None:
                 "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
                 "name": "example.com",
                 "status": "not_started",
-                "created_at": "2023-04-26T20:21:26.347412+00:00",
+                "created_at": "2023-04-26 20:21:26.347412+00",
                 "region": "us-east-1",
             }
         )
@@ -282,7 +282,7 @@ async def test_domains_update_async(self) -> None:
         assert domain["id"] == "d91cd9bd-1176-453e-8fc1-35364d380206"
         assert domain["name"] == "example.com"
         assert domain["status"] == "not_started"
-        assert domain["created_at"] == "2023-04-26T20:21:26.347412+00:00"
+        assert domain["created_at"] == "2023-04-26 20:21:26.347412+00"
         assert domain["region"] == "us-east-1"
 
     async def test_domains_update_async_with_tracking_subdomain(self) -> None:
@@ -318,7 +318,7 @@ async def test_domains_remove_async(self) -> None:
                 "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
                 "name": "example.com",
                 "status": "not_started",
-                "created_at": "2023-04-26T20:21:26.347412+00:00",
+                "created_at": "2023-04-26 20:21:26.347412+00",
                 "region": "us-east-1",
             }
         )
@@ -329,7 +329,7 @@ async def test_domains_remove_async(self) -> None:
         assert domain["id"] == "d91cd9bd-1176-453e-8fc1-35364d380206"
         assert domain["name"] == "example.com"
         assert domain["status"] == "not_started"
-        assert domain["created_at"] == "2023-04-26T20:21:26.347412+00:00"
+        assert domain["created_at"] == "2023-04-26 20:21:26.347412+00"
         assert domain["region"] == "us-east-1"
 
     async def test_should_remove_domains_async_raise_exception_when_no_content(
@@ -348,7 +348,7 @@ async def test_domains_verify_async(self) -> None:
                 "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
                 "name": "example.com",
                 "status": "verified",
-                "created_at": "2023-04-26T20:21:26.347412+00:00",
+                "created_at": "2023-04-26 20:21:26.347412+00",
                 "region": "us-east-1",
             }
         )
@@ -359,7 +359,7 @@ async def test_domains_verify_async(self) -> None:
         assert domain["id"] == "d91cd9bd-1176-453e-8fc1-35364d380206"
         assert domain["name"] == "example.com"
         assert domain["status"] == "verified"
-        assert domain["created_at"] == "2023-04-26T20:21:26.347412+00:00"
+        assert domain["created_at"] == "2023-04-26 20:21:26.347412+00"
         assert domain["region"] == "us-east-1"
 
     async def test_should_verify_domains_async_raise_exception_when_no_content(
diff --git a/tests/domains_test.py b/tests/domains_test.py
index 8694662..53ae913 100644
--- a/tests/domains_test.py
+++ b/tests/domains_test.py
@@ -11,7 +11,7 @@ def test_domains_create(self) -> None:
             {
                 "id": "4dd369bc-aa82-4ff3-97de-514ae3000ee0",
                 "name": "example.com",
-                "created_at": "2023-03-28T17:12:02.059593+00:00",
+                "created_at": "2023-03-28 17:12:02.059593+00",
                 "status": "not_started",
                 "records": [
                     {
@@ -71,7 +71,7 @@ def test_domains_create(self) -> None:
         assert domain["id"] == "4dd369bc-aa82-4ff3-97de-514ae3000ee0"
         assert domain["name"] == "example.com"
         assert domain["status"] == "not_started"
-        assert domain["created_at"] == "2023-03-28T17:12:02.059593+00:00"
+        assert domain["created_at"] == "2023-03-28 17:12:02.059593+00"
         assert domain["region"] == "us-east-1"
 
     def test_should_create_domains_raise_exception_when_no_content(self) -> None:
@@ -89,7 +89,7 @@ def test_domains_get(self) -> None:
                 "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
                 "name": "example.com",
                 "status": "not_started",
-                "created_at": "2023-04-26T20:21:26.347412+00:00",
+                "created_at": "2023-04-26 20:21:26.347412+00",
                 "region": "us-east-1",
             }
         )
@@ -100,7 +100,7 @@ def test_domains_get(self) -> None:
         assert domain["id"] == "d91cd9bd-1176-453e-8fc1-35364d380206"
         assert domain["name"] == "example.com"
         assert domain["status"] == "not_started"
-        assert domain["created_at"] == "2023-04-26T20:21:26.347412+00:00"
+        assert domain["created_at"] == "2023-04-26 20:21:26.347412+00"
         assert domain["region"] == "us-east-1"
 
     def test_should_get_domains_raise_exception_when_no_content(self) -> None:
@@ -120,7 +120,7 @@ def test_domains_list(self) -> None:
                         "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
                         "name": "example.com",
                         "status": "not_started",
-                        "created_at": "2023-04-26T20:21:26.347412+00:00",
+                        "created_at": "2023-04-26 20:21:26.347412+00",
                         "region": "us-east-1",
                     }
                 ],
@@ -133,7 +133,7 @@ def test_domains_list(self) -> None:
         assert domains["data"][0]["id"] == "d91cd9bd-1176-453e-8fc1-35364d380206"
         assert domains["data"][0]["name"] == "example.com"
         assert domains["data"][0]["status"] == "not_started"
-        assert domains["data"][0]["created_at"] == "2023-04-26T20:21:26.347412+00:00"
+        assert domains["data"][0]["created_at"] == "2023-04-26 20:21:26.347412+00"
         assert domains["data"][0]["region"] == "us-east-1"
 
     def test_should_list_domains_raise_exception_when_no_content(self) -> None:
@@ -185,7 +185,7 @@ def test_domains_create_with_tracking_subdomain(self) -> None:
             {
                 "id": "4dd369bc-aa82-4ff3-97de-514ae3000ee0",
                 "name": "example.com",
-                "created_at": "2023-03-28T17:12:02.059593+00:00",
+                "created_at": "2023-03-28 17:12:02.059593+00",
                 "status": "not_started",
                 "open_tracking": True,
                 "click_tracking": True,
@@ -256,7 +256,7 @@ def test_domains_get_with_tracking_fields(self) -> None:
                 "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
                 "name": "example.com",
                 "status": "not_started",
-                "created_at": "2023-04-26T20:21:26.347412+00:00",
+                "created_at": "2023-04-26 20:21:26.347412+00",
                 "region": "us-east-1",
                 "open_tracking": True,
                 "click_tracking": True,
@@ -348,14 +348,14 @@ def test_domains_list_with_pagination_params(self) -> None:
                         "id": "domain-1",
                         "name": "example1.com",
                         "status": "verified",
-                        "created_at": "2023-04-26T20:21:26.347412+00:00",
+                        "created_at": "2023-04-26 20:21:26.347412+00",
                         "region": "us-east-1",
                     },
                     {
                         "id": "domain-2",
                         "name": "example2.com",
                         "status": "not_started",
-                        "created_at": "2023-04-27T20:21:26.347412+00:00",
+                        "created_at": "2023-04-27 20:21:26.347412+00",
                         "region": "us-west-2",
                     },
                 ],
@@ -380,7 +380,7 @@ def test_domains_list_with_before_param(self) -> None:
                         "id": "domain-3",
                         "name": "example3.com",
                         "status": "verified",
-                        "created_at": "2023-04-25T20:21:26.347412+00:00",
+                        "created_at": "2023-04-25 20:21:26.347412+00",
                         "region": "eu-west-1",
                     }
                 ],
diff --git a/tests/emails_test.py b/tests/emails_test.py
index cc94caa..b7f492b 100644
--- a/tests/emails_test.py
+++ b/tests/emails_test.py
@@ -43,7 +43,7 @@ def test_email_get(self) -> None:
                 "message_id": "<111-222-333@email.example.com>",
                 "to": ["james@bond.com"],
                 "from": "onboarding@resend.dev",
-                "created_at": "2023-04-03T22:13:42.674981+00:00",
+                "created_at": "2023-04-03 22:13:42.674981+00",
                 "subject": "Hello World",
                 "html": "Congrats on sending your <strong>first email</strong>!",
                 "text": None,
@@ -150,7 +150,7 @@ def test_email_list(self) -> None:
                         "message_id": "<111-222-333@email.example.com>",
                         "to": ["james@bond.com"],
                         "from": "onboarding@resend.dev",
-                        "created_at": "2023-04-03T22:13:42.674981+00:00",
+                        "created_at": "2023-04-03 22:13:42.674981+00",
                         "subject": "Hello World",
                         "html": "Congrats on sending your <strong>first email</strong>!",
                         "text": None,
@@ -164,7 +164,7 @@ def test_email_list(self) -> None:
                         "message_id": "<222-333-444@email.example.com>",
                         "to": ["test@example.com"],
                         "from": "hello@resend.dev",
-                        "created_at": "2023-04-04T10:15:42.674981+00:00",
+                        "created_at": "2023-04-04 10:15:42.674981+00",
                         "subject": "Test Email",
                         "html": "This is a test email",
                         "text": "This is a test email",
@@ -195,7 +195,7 @@ def test_email_list_with_params(self) -> None:
                         "id": "4ef9a417-02e9-4d39-ad75-9611e0fcc33c",
                         "to": ["james@bond.com"],
                         "from": "onboarding@resend.dev",
-                        "created_at": "2023-04-03T22:13:42.674981+00:00",
+                        "created_at": "2023-04-03 22:13:42.674981+00",
                         "subject": "Hello World",
                         "html": "Congrats on sending your <strong>first email</strong>!",
                         "text": None,
@@ -248,7 +248,7 @@ def test_receiving_get(self) -> None:
                 "id": "67d9bcdb-5a02-42d7-8da9-0d6feea18cff",
                 "to": ["received@example.com"],
                 "from": "sender@example.com",
-                "created_at": "2023-04-07T23:13:52.669661+00:00",
+                "created_at": "2023-04-07 23:13:52.669661+00",
                 "subject": "Test inbound email",
                 "html": "<p>hello world</p>",
                 "text": "hello world",
@@ -296,7 +296,7 @@ def test_receiving_get_with_no_attachments(self) -> None:
                 "id": "67d9bcdb-5a02-42d7-8da9-0d6feea18cff",
                 "to": ["received@example.com"],
                 "from": "sender@example.com",
-                "created_at": "2023-04-07T23:13:52.669661+00:00",
+                "created_at": "2023-04-07 23:13:52.669661+00",
                 "subject": "Test inbound email",
                 "html": None,
                 "text": "hello world",
@@ -328,7 +328,7 @@ def test_receiving_get_with_nullable_attachment_fields(self) -> None:
                 "id": "67d9bcdb-5a02-42d7-8da9-0d6feea18cff",
                 "to": ["received@example.com"],
                 "from": "sender@example.com",
-                "created_at": "2023-04-07T23:13:52.669661+00:00",
+                "created_at": "2023-04-07 23:13:52.669661+00",
                 "subject": "Signed inbound email",
                 "html": None,
                 "text": "hello world",
@@ -380,7 +380,7 @@ def test_receiving_get_with_html_format_cid(self) -> None:
                 "id": "67d9bcdb-5a02-42d7-8da9-0d6feea18cff",
                 "to": ["received@example.com"],
                 "from": "sender@example.com",
-                "created_at": "2023-04-07T23:13:52.669661+00:00",
+                "created_at": "2023-04-07 23:13:52.669661+00",
                 "subject": "Test inbound email",
                 "html": '<img src="cid:img001" />',
                 "text": "hello world",
@@ -408,7 +408,7 @@ def test_receiving_get_with_html_format_data_uri(self) -> None:
                 "id": "67d9bcdb-5a02-42d7-8da9-0d6feea18cff",
                 "to": ["received@example.com"],
                 "from": "sender@example.com",
-                "created_at": "2023-04-07T23:13:52.669661+00:00",
+                "created_at": "2023-04-07 23:13:52.669661+00",
                 "subject": "Test inbound email",
                 "html": '<img src="data:image/png;base64,abc" />',
                 "text": "hello world",
@@ -620,7 +620,7 @@ def test_receiving_get_email_headers_not_overwritten_by_http_headers(self) -> No
         mock_client.request.return_value = (
             b'{"object":"inbound","id":"67d9bcdb-5a02-42d7-8da9-0d6feea18cff",'
             b'"to":["received@example.com"],"from":"sender@example.com",'
-            b'"created_at":"2023-04-07T23:13:52.669661+00:00","subject":"Test",'
+            b'"created_at":"2023-04-07 23:13:52.669661+00","subject":"Test",'
             b'"html":null,"text":"hello","bcc":null,"cc":null,"reply_to":null,'
             b'"message_id":"<msg123>","headers":{"X-Custom":"email-value"},'
             b'"attachments":[]}',
diff --git a/tests/events_async_test.py b/tests/events_async_test.py
index 6c1e765..064cf53 100644
--- a/tests/events_async_test.py
+++ b/tests/events_async_test.py
@@ -38,7 +38,7 @@ async def test_events_get_async(self) -> None:
                 "id": "56261eea-8f8b-4381-83c6-79fa7120f1cf",
                 "name": "user.signed_up",
                 "schema": {"plan": "string"},
-                "created_at": "2024-01-01T00:00:00.000Z",
+                "created_at": "2024-01-01 00:00:00+00",
                 "updated_at": None,
             }
         )
@@ -129,7 +129,7 @@ async def test_events_list_async(self) -> None:
                         "id": "56261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "name": "user.signed_up",
                         "schema": None,
-                        "created_at": "2024-01-01T00:00:00.000Z",
+                        "created_at": "2024-01-01 00:00:00+00",
                         "updated_at": None,
                     },
                 ],
diff --git a/tests/events_test.py b/tests/events_test.py
index d6e3514..c543917 100644
--- a/tests/events_test.py
+++ b/tests/events_test.py
@@ -46,7 +46,7 @@ def test_events_get_by_id(self) -> None:
                 "id": "56261eea-8f8b-4381-83c6-79fa7120f1cf",
                 "name": "user.signed_up",
                 "schema": {"plan": "string"},
-                "created_at": "2024-01-01T00:00:00.000Z",
+                "created_at": "2024-01-01 00:00:00+00",
                 "updated_at": None,
             }
         )
@@ -56,7 +56,7 @@ def test_events_get_by_id(self) -> None:
         assert event["id"] == "56261eea-8f8b-4381-83c6-79fa7120f1cf"
         assert event["name"] == "user.signed_up"
         assert event["schema"] == {"plan": "string"}
-        assert event["created_at"] == "2024-01-01T00:00:00.000Z"
+        assert event["created_at"] == "2024-01-01 00:00:00+00"
         assert event["updated_at"] is None
 
     def test_events_get_by_name(self) -> None:
@@ -66,7 +66,7 @@ def test_events_get_by_name(self) -> None:
                 "id": "56261eea-8f8b-4381-83c6-79fa7120f1cf",
                 "name": "user.signed_up",
                 "schema": None,
-                "created_at": "2024-01-01T00:00:00.000Z",
+                "created_at": "2024-01-01 00:00:00+00",
                 "updated_at": None,
             }
         )
@@ -189,15 +189,15 @@ def test_events_list(self) -> None:
                         "id": "56261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "name": "user.signed_up",
                         "schema": {"plan": "string"},
-                        "created_at": "2024-01-01T00:00:00.000Z",
+                        "created_at": "2024-01-01 00:00:00+00",
                         "updated_at": None,
                     },
                     {
                         "id": "67372ffb-9g9c-5492-94d7-80gb8231g2dg",
                         "name": "user.upgraded",
                         "schema": None,
-                        "created_at": "2024-02-01T00:00:00.000Z",
-                        "updated_at": "2024-02-15T00:00:00.000Z",
+                        "created_at": "2024-02-01 00:00:00+00",
+                        "updated_at": "2024-02-15 00:00:00+00",
                     },
                 ],
             }
@@ -217,7 +217,7 @@ def test_events_list(self) -> None:
         second = events["data"][1]
         assert second["name"] == "user.upgraded"
         assert second["schema"] is None
-        assert second["updated_at"] == "2024-02-15T00:00:00.000Z"
+        assert second["updated_at"] == "2024-02-15 00:00:00+00"
 
     def test_events_list_with_pagination_params(self) -> None:
         self.set_mock_json(
@@ -229,7 +229,7 @@ def test_events_list_with_pagination_params(self) -> None:
                         "id": "56261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "name": "user.signed_up",
                         "schema": None,
-                        "created_at": "2024-01-01T00:00:00.000Z",
+                        "created_at": "2024-01-01 00:00:00+00",
                         "updated_at": None,
                     }
                 ],
diff --git a/tests/logs_async_test.py b/tests/logs_async_test.py
index 3883454..494c55b 100644
--- a/tests/logs_async_test.py
+++ b/tests/logs_async_test.py
@@ -15,7 +15,7 @@ async def test_logs_get_async(self) -> None:
             {
                 "object": "log",
                 "id": "37e4414c-5e25-4dbc-a071-43552a4bd53b",
-                "created_at": "2024-01-01T00:00:00.000000+00:00",
+                "created_at": "2024-01-01 00:00:00+00",
                 "endpoint": "/emails",
                 "method": "POST",
                 "response_status": 200,
@@ -49,7 +49,7 @@ async def test_logs_list_async(self) -> None:
                 "data": [
                     {
                         "id": "37e4414c-5e25-4dbc-a071-43552a4bd53b",
-                        "created_at": "2024-01-01T00:00:00.000000+00:00",
+                        "created_at": "2024-01-01 00:00:00+00",
                         "endpoint": "/emails",
                         "method": "POST",
                         "response_status": 200,
@@ -81,7 +81,7 @@ async def test_logs_list_async_with_pagination_params(self) -> None:
                 "data": [
                     {
                         "id": "log-id-1",
-                        "created_at": "2024-01-01T00:00:00.000000+00:00",
+                        "created_at": "2024-01-01 00:00:00+00",
                         "endpoint": "/emails",
                         "method": "POST",
                         "response_status": 200,
diff --git a/tests/logs_test.py b/tests/logs_test.py
index 3a7ba8b..39e88eb 100644
--- a/tests/logs_test.py
+++ b/tests/logs_test.py
@@ -11,7 +11,7 @@ def test_logs_get(self) -> None:
             {
                 "object": "log",
                 "id": "37e4414c-5e25-4dbc-a071-43552a4bd53b",
-                "created_at": "2024-01-01T00:00:00.000000+00:00",
+                "created_at": "2024-01-01 00:00:00+00",
                 "endpoint": "/emails",
                 "method": "POST",
                 "response_status": 200,
@@ -26,7 +26,7 @@ def test_logs_get(self) -> None:
         )
         assert log["object"] == "log"
         assert log["id"] == "37e4414c-5e25-4dbc-a071-43552a4bd53b"
-        assert log["created_at"] == "2024-01-01T00:00:00.000000+00:00"
+        assert log["created_at"] == "2024-01-01 00:00:00+00"
         assert log["endpoint"] == "/emails"
         assert log["method"] == "POST"
         assert log["response_status"] == 200
@@ -47,7 +47,7 @@ def test_logs_list(self) -> None:
                 "data": [
                     {
                         "id": "37e4414c-5e25-4dbc-a071-43552a4bd53b",
-                        "created_at": "2024-01-01T00:00:00.000000+00:00",
+                        "created_at": "2024-01-01 00:00:00+00",
                         "endpoint": "/emails",
                         "method": "POST",
                         "response_status": 200,
@@ -63,7 +63,7 @@ def test_logs_list(self) -> None:
         assert len(logs["data"]) == 1
         log = logs["data"][0]
         assert log["id"] == "37e4414c-5e25-4dbc-a071-43552a4bd53b"
-        assert log["created_at"] == "2024-01-01T00:00:00.000000+00:00"
+        assert log["created_at"] == "2024-01-01 00:00:00+00"
         assert log["endpoint"] == "/emails"
         assert log["method"] == "POST"
         assert log["response_status"] == 200
@@ -82,7 +82,7 @@ def test_logs_list_with_pagination_params(self) -> None:
                 "data": [
                     {
                         "id": "log-id-1",
-                        "created_at": "2024-01-01T00:00:00.000000+00:00",
+                        "created_at": "2024-01-01 00:00:00+00",
                         "endpoint": "/emails",
                         "method": "POST",
                         "response_status": 200,
@@ -90,7 +90,7 @@ def test_logs_list_with_pagination_params(self) -> None:
                     },
                     {
                         "id": "log-id-2",
-                        "created_at": "2024-01-02T00:00:00.000000+00:00",
+                        "created_at": "2024-01-02 00:00:00+00",
                         "endpoint": "/domains",
                         "method": "GET",
                         "response_status": 200,
@@ -116,7 +116,7 @@ def test_logs_list_with_before_param(self) -> None:
                 "data": [
                     {
                         "id": "log-id-3",
-                        "created_at": "2024-01-03T00:00:00.000000+00:00",
+                        "created_at": "2024-01-03 00:00:00+00",
                         "endpoint": "/api-keys",
                         "method": "DELETE",
                         "response_status": 200,
diff --git a/tests/oauth_grants_async_test.py b/tests/oauth_grants_async_test.py
index 2ea82a4..0dc0472 100644
--- a/tests/oauth_grants_async_test.py
+++ b/tests/oauth_grants_async_test.py
@@ -20,7 +20,7 @@ async def test_oauth_grants_list_async(self) -> None:
                         "id": "650e8400-e29b-41d4-a716-446655440001",
                         "client_id": "430eed87-632a-4ea6-90db-0aace67ec228",
                         "scopes": ["emails:send"],
-                        "created_at": "2023-06-21T06:10:36.144Z",
+                        "created_at": "2023-06-21 06:10:36.144+00",
                         "revoked_at": None,
                         "revoked_reason": None,
                         "client": {
diff --git a/tests/oauth_grants_test.py b/tests/oauth_grants_test.py
index 031b45b..e09fa72 100644
--- a/tests/oauth_grants_test.py
+++ b/tests/oauth_grants_test.py
@@ -16,7 +16,7 @@ def test_oauth_grants_list(self) -> None:
                         "id": "650e8400-e29b-41d4-a716-446655440001",
                         "client_id": "430eed87-632a-4ea6-90db-0aace67ec228",
                         "scopes": ["emails:send"],
-                        "created_at": "2023-06-21T06:10:36.144Z",
+                        "created_at": "2023-06-21 06:10:36.144+00",
                         "revoked_at": None,
                         "revoked_reason": None,
                         "client": {
@@ -35,7 +35,7 @@ def test_oauth_grants_list(self) -> None:
             assert grant["id"] == "650e8400-e29b-41d4-a716-446655440001"
             assert grant["client_id"] == "430eed87-632a-4ea6-90db-0aace67ec228"
             assert grant["scopes"] == ["emails:send"]
-            assert grant["created_at"] == "2023-06-21T06:10:36.144Z"
+            assert grant["created_at"] == "2023-06-21 06:10:36.144+00"
             assert grant["revoked_at"] is None
             assert grant["revoked_reason"] is None
             assert grant["client"]["name"] == "Resend CLI"
@@ -51,8 +51,8 @@ def test_oauth_grants_list_revoked_grant(self) -> None:
                         "id": "650e8400-e29b-41d4-a716-446655440002",
                         "client_id": "430eed87-632a-4ea6-90db-0aace67ec228",
                         "scopes": ["emails:send", "domains:read"],
-                        "created_at": "2023-06-20T06:10:36.144Z",
-                        "revoked_at": "2023-06-22T06:10:36.144Z",
+                        "created_at": "2023-06-20 06:10:36.144+00",
+                        "revoked_at": "2023-06-22 06:10:36.144+00",
                         "revoked_reason": "revoked_from_api",
                         "client": {
                             "name": "Resend CLI",
@@ -65,7 +65,7 @@ def test_oauth_grants_list_revoked_grant(self) -> None:
 
         grants: resend.OAuthGrants.ListResponse = resend.OAuthGrants.list()
         grant = grants["data"][0]
-        assert grant["revoked_at"] == "2023-06-22T06:10:36.144Z"
+        assert grant["revoked_at"] == "2023-06-22 06:10:36.144+00"
         assert grant["revoked_reason"] == "revoked_from_api"
         assert grant["client"]["logo_uri"] is None
 
@@ -84,7 +84,7 @@ def test_oauth_grants_list_with_pagination_params(self) -> None:
                         "id": "grant-1",
                         "client_id": "client-1",
                         "scopes": ["emails:send"],
-                        "created_at": "2023-06-21T06:10:36.144Z",
+                        "created_at": "2023-06-21 06:10:36.144+00",
                         "revoked_at": None,
                         "revoked_reason": None,
                         "client": {"name": "Resend CLI", "logo_uri": None},
@@ -93,7 +93,7 @@ def test_oauth_grants_list_with_pagination_params(self) -> None:
                         "id": "grant-2",
                         "client_id": "client-1",
                         "scopes": ["emails:send"],
-                        "created_at": "2023-06-20T06:10:36.144Z",
+                        "created_at": "2023-06-20 06:10:36.144+00",
                         "revoked_at": None,
                         "revoked_reason": None,
                         "client": {"name": "Resend CLI", "logo_uri": None},
@@ -123,7 +123,7 @@ def test_oauth_grants_list_with_before_param(self) -> None:
                         "id": "grant-3",
                         "client_id": "client-1",
                         "scopes": ["emails:send"],
-                        "created_at": "2023-06-19T06:10:36.144Z",
+                        "created_at": "2023-06-19 06:10:36.144+00",
                         "revoked_at": None,
                         "revoked_reason": None,
                         "client": {"name": "Resend CLI", "logo_uri": None},
diff --git a/tests/receiving_async_test.py b/tests/receiving_async_test.py
index 5b7dfb5..ff210a8 100644
--- a/tests/receiving_async_test.py
+++ b/tests/receiving_async_test.py
@@ -19,7 +19,7 @@ async def test_receiving_get_async(self) -> None:
                 "from": "sender@example.com",
                 "to": ["recipient@example.com"],
                 "subject": "Test subject",
-                "created_at": "2024-01-01T00:00:00Z",
+                "created_at": "2024-01-01 00:00:00+00",
                 "received_for": ["forwarded@example.com"],
             }
         )
@@ -39,7 +39,7 @@ async def test_receiving_get_async_with_html_format_cid(self) -> None:
                 "from": "sender@example.com",
                 "to": ["recipient@example.com"],
                 "subject": "Test subject",
-                "created_at": "2024-01-01T00:00:00Z",
+                "created_at": "2024-01-01 00:00:00+00",
             }
         )
 
@@ -61,7 +61,7 @@ async def test_receiving_get_async_with_html_format_data_uri(self) -> None:
                 "from": "sender@example.com",
                 "to": ["recipient@example.com"],
                 "subject": "Test subject",
-                "created_at": "2024-01-01T00:00:00Z",
+                "created_at": "2024-01-01 00:00:00+00",
             }
         )
 
@@ -95,7 +95,7 @@ async def test_receiving_list_async(self) -> None:
                         "from": "sender@example.com",
                         "to": ["recipient@example.com"],
                         "subject": "Test subject",
-                        "created_at": "2024-01-01T00:00:00Z",
+                        "created_at": "2024-01-01 00:00:00+00",
                     }
                 ],
             }
@@ -126,7 +126,7 @@ async def test_receiving_attachments_get_async(self) -> None:
                 "content_disposition": "inline",
                 "content_id": "img001",
                 "download_url": "https://inbound-cdn.resend.com/test/attachments/test-id",
-                "expires_at": "2025-10-17T14:29:41.521Z",
+                "expires_at": "2025-10-17 14:29:41.521+00",
             }
         )
 
@@ -164,7 +164,7 @@ async def test_receiving_attachments_list_async(self) -> None:
                         "content_id": "img001",
                         "size": 1024,
                         "download_url": "https://inbound-cdn.resend.com/test/attachments/2a0c9ce0?signature=sig-123",
-                        "expires_at": "2025-10-17T14:29:41.521Z",
+                        "expires_at": "2025-10-17 14:29:41.521+00",
                     },
                     {
                         "id": "3b1d0df1-4223-5839-a87f-58eecd27b429",
@@ -173,7 +173,7 @@ async def test_receiving_attachments_list_async(self) -> None:
                         "content_disposition": "attachment",
                         "size": 2048,
                         "download_url": "https://inbound-cdn.resend.com/test/attachments/3b1d0df1?signature=sig-456",
-                        "expires_at": "2025-10-17T14:29:41.521Z",
+                        "expires_at": "2025-10-17 14:29:41.521+00",
                     },
                 ],
             }
diff --git a/tests/response_test.py b/tests/response_test.py
index 32e1d34..ae9b693 100644
--- a/tests/response_test.py
+++ b/tests/response_test.py
@@ -19,7 +19,7 @@ def test_list_response_supports_dict_access(self) -> None:
                         "content_disposition": "inline",
                         "size": 1024,
                         "download_url": "https://cdn.resend.com/att-1",
-                        "expires_at": "2025-10-17T14:29:41.521Z",
+                        "expires_at": "2025-10-17 14:29:41.521+00",
                     },
                 ],
             }
@@ -45,7 +45,7 @@ def test_list_response_supports_attribute_access(self) -> None:
                         "content_disposition": "inline",
                         "size": 1024,
                         "download_url": "https://cdn.resend.com/att-1",
-                        "expires_at": "2025-10-17T14:29:41.521Z",
+                        "expires_at": "2025-10-17 14:29:41.521+00",
                     },
                 ],
             }
diff --git a/tests/segments_test.py b/tests/segments_test.py
index baf3122..7f3c9fa 100644
--- a/tests/segments_test.py
+++ b/tests/segments_test.py
@@ -36,14 +36,14 @@ def test_segments_get(self) -> None:
                 "object": "audience",
                 "id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                 "name": "Registered Users",
-                "created_at": "2023-10-06T22:59:55.977Z",
+                "created_at": "2023-10-06 22:59:55.977+00",
             }
         )
 
         segment = resend.Segments.get(id="78261eea-8f8b-4381-83c6-79fa7120f1cf")
         assert segment["id"] == "78261eea-8f8b-4381-83c6-79fa7120f1cf"
         assert segment["name"] == "Registered Users"
-        assert segment["created_at"] == "2023-10-06T22:59:55.977Z"
+        assert segment["created_at"] == "2023-10-06 22:59:55.977+00"
 
     def test_should_get_segments_raise_exception_when_no_content(self) -> None:
         self.set_mock_json(None)
@@ -80,7 +80,7 @@ def test_segments_list(self) -> None:
                     {
                         "id": "78261eea-8f8b-4381-83c6-79fa7120f1cf",
                         "name": "Registered Users",
-                        "created_at": "2023-10-06T22:59:55.977Z",
+                        "created_at": "2023-10-06 22:59:55.977+00",
                     }
                 ],
             }
@@ -106,12 +106,12 @@ def test_segments_list_with_pagination_params(self) -> None:
                     {
                         "id": "segment-1",
                         "name": "First Segment",
-                        "created_at": "2023-10-06T22:59:55.977Z",
+                        "created_at": "2023-10-06 22:59:55.977+00",
                     },
                     {
                         "id": "segment-2",
                         "name": "Second Segment",
-                        "created_at": "2023-10-07T22:59:55.977Z",
+                        "created_at": "2023-10-07 22:59:55.977+00",
                     },
                 ],
             }
@@ -137,7 +137,7 @@ def test_segments_list_with_before_param(self) -> None:
                     {
                         "id": "segment-3",
                         "name": "Third Segment",
-                        "created_at": "2023-10-05T22:59:55.977Z",
+                        "created_at": "2023-10-05 22:59:55.977+00",
                     }
                 ],
             }
diff --git a/tests/suppressions_async_test.py b/tests/suppressions_async_test.py
index ba28c69..7828319 100644
--- a/tests/suppressions_async_test.py
+++ b/tests/suppressions_async_test.py
@@ -45,14 +45,14 @@ async def test_suppressions_list_async(self) -> None:
                         "email": "bounced@example.com",
                         "origin": "bounce",
                         "source_id": "479e3145-dd38-476b-932c-529ceb705947",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                     },
                     {
                         "id": "fd61172c-cafc-40f5-b049-b45947779a29",
                         "email": "manual@example.com",
                         "origin": "manual",
                         "source_id": None,
-                        "created_at": "2023-10-07T23:47:56.678Z",
+                        "created_at": "2023-10-07 23:47:56.678+00",
                     },
                 ],
             }
@@ -98,7 +98,7 @@ async def test_suppressions_get_async(self) -> None:
                 "email": "bounced@example.com",
                 "origin": "bounce",
                 "source_id": "479e3145-dd38-476b-932c-529ceb705947",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
             }
         )
 
@@ -117,7 +117,7 @@ async def test_suppressions_get_async_with_null_source_id(self) -> None:
                 "email": "manual@example.com",
                 "origin": "manual",
                 "source_id": None,
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
             }
         )
 
@@ -133,7 +133,7 @@ async def test_suppressions_get_async_encodes_email_identifier(self) -> None:
                 "email": "user+tag@example.com",
                 "origin": "manual",
                 "source_id": None,
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
             }
         )
 
diff --git a/tests/suppressions_test.py b/tests/suppressions_test.py
index 0b37133..4ffe655 100644
--- a/tests/suppressions_test.py
+++ b/tests/suppressions_test.py
@@ -43,14 +43,14 @@ def test_suppressions_list(self) -> None:
                         "email": "bounced@example.com",
                         "origin": "bounce",
                         "source_id": "479e3145-dd38-476b-932c-529ceb705947",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                     },
                     {
                         "id": "fd61172c-cafc-40f5-b049-b45947779a29",
                         "email": "manual@example.com",
                         "origin": "manual",
                         "source_id": None,
-                        "created_at": "2023-10-07T23:47:56.678Z",
+                        "created_at": "2023-10-07 23:47:56.678+00",
                     },
                 ],
             }
@@ -65,7 +65,7 @@ def test_suppressions_list(self) -> None:
         assert bounced["email"] == "bounced@example.com"
         assert bounced["origin"] == "bounce"
         assert bounced["source_id"] == "479e3145-dd38-476b-932c-529ceb705947"
-        assert bounced["created_at"] == "2023-10-06T23:47:56.678Z"
+        assert bounced["created_at"] == "2023-10-06 23:47:56.678+00"
 
         manual = suppressions["data"][1]
         assert manual["origin"] == "manual"
@@ -82,7 +82,7 @@ def test_suppressions_list_entries_have_no_object_field(self) -> None:
                         "email": "bounced@example.com",
                         "origin": "bounce",
                         "source_id": "479e3145-dd38-476b-932c-529ceb705947",
-                        "created_at": "2023-10-06T23:47:56.678Z",
+                        "created_at": "2023-10-06 23:47:56.678+00",
                     }
                 ],
             }
@@ -126,7 +126,7 @@ def test_suppressions_get(self) -> None:
                 "email": "bounced@example.com",
                 "origin": "bounce",
                 "source_id": "479e3145-dd38-476b-932c-529ceb705947",
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
             }
         )
 
@@ -147,7 +147,7 @@ def test_suppressions_get_with_null_source_id(self) -> None:
                 "email": "manual@example.com",
                 "origin": "manual",
                 "source_id": None,
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
             }
         )
 
@@ -163,7 +163,7 @@ def test_suppressions_get_encodes_email_identifier(self) -> None:
                 "email": "user+tag@example.com",
                 "origin": "manual",
                 "source_id": None,
-                "created_at": "2023-10-06T23:47:56.678Z",
+                "created_at": "2023-10-06 23:47:56.678+00",
             }
         )
 
diff --git a/tests/templates_async_test.py b/tests/templates_async_test.py
index 66b5e59..75f8129 100644
--- a/tests/templates_async_test.py
+++ b/tests/templates_async_test.py
@@ -72,9 +72,9 @@ async def test_templates_get_async(self) -> None:
                         "fallback_value": 25,
                     },
                 ],
-                "created_at": "2024-01-15T10:30:00.000Z",
-                "updated_at": "2024-01-15T10:30:00.000Z",
-                "published_at": "2024-01-15T11:00:00.000Z",
+                "created_at": "2024-01-15 10:30:00+00",
+                "updated_at": "2024-01-15 10:30:00+00",
+                "published_at": "2024-01-15 11:00:00+00",
             }
         )
 
@@ -196,9 +196,9 @@ async def test_templates_list_async(self) -> None:
                         "id": "template-1",
                         "name": "welcome-email",
                         "status": "published",
-                        "published_at": "2024-01-15T11:00:00.000Z",
-                        "created_at": "2024-01-15T10:30:00.000Z",
-                        "updated_at": "2024-01-15T10:30:00.000Z",
+                        "published_at": "2024-01-15 11:00:00+00",
+                        "created_at": "2024-01-15 10:30:00+00",
+                        "updated_at": "2024-01-15 10:30:00+00",
                         "alias": "welcome",
                     }
                 ],
diff --git a/tests/templates_test.py b/tests/templates_test.py
index ca1550d..f2f598b 100644
--- a/tests/templates_test.py
+++ b/tests/templates_test.py
@@ -79,9 +79,9 @@ def test_templates_get(self) -> None:
                         "fallback_value": 25,
                     },
                 ],
-                "created_at": "2024-01-15T10:30:00.000Z",
-                "updated_at": "2024-01-15T10:30:00.000Z",
-                "published_at": "2024-01-15T11:00:00.000Z",
+                "created_at": "2024-01-15 10:30:00+00",
+                "updated_at": "2024-01-15 10:30:00+00",
+                "published_at": "2024-01-15 11:00:00+00",
             }
         )
 
@@ -105,9 +105,9 @@ def test_templates_get(self) -> None:
         assert template["variables"][1]["key"] == "AGE"
         assert template["variables"][1]["type"] == "number"
         assert template["variables"][1]["fallback_value"] == 25
-        assert template["created_at"] == "2024-01-15T10:30:00.000Z"
-        assert template["updated_at"] == "2024-01-15T10:30:00.000Z"
-        assert template["published_at"] == "2024-01-15T11:00:00.000Z"
+        assert template["created_at"] == "2024-01-15 10:30:00+00"
+        assert template["updated_at"] == "2024-01-15 10:30:00+00"
+        assert template["published_at"] == "2024-01-15 11:00:00+00"
 
     def test_templates_update(self) -> None:
         self.set_mock_json(
@@ -171,9 +171,9 @@ def test_templates_list(self) -> None:
                         "id": "template-1",
                         "name": "welcome-email",
                         "status": "published",
-                        "published_at": "2024-01-15T11:00:00.000Z",
-                        "created_at": "2024-01-15T10:30:00.000Z",
-                        "updated_at": "2024-01-15T10:30:00.000Z",
+                        "published_at": "2024-01-15 11:00:00+00",
+                        "created_at": "2024-01-15 10:30:00+00",
+                        "updated_at": "2024-01-15 10:30:00+00",
                         "alias": "welcome",
                     },
                     {
@@ -181,8 +181,8 @@ def test_templates_list(self) -> None:
                         "name": "goodbye-email",
                         "status": "draft",
                         "published_at": None,
-                        "created_at": "2024-01-16T10:30:00.000Z",
-                        "updated_at": "2024-01-16T10:30:00.000Z",
+                        "created_at": "2024-01-16 10:30:00+00",
+                        "updated_at": "2024-01-16 10:30:00+00",
                         "alias": "goodbye",
                     },
                 ],
@@ -198,9 +198,9 @@ def test_templates_list(self) -> None:
         assert template["id"] == "template-1"
         assert template["name"] == "welcome-email"
         assert template["status"] == "published"
-        assert template["published_at"] == "2024-01-15T11:00:00.000Z"
-        assert template["created_at"] == "2024-01-15T10:30:00.000Z"
-        assert template["updated_at"] == "2024-01-15T10:30:00.000Z"
+        assert template["published_at"] == "2024-01-15 11:00:00+00"
+        assert template["created_at"] == "2024-01-15 10:30:00+00"
+        assert template["updated_at"] == "2024-01-15 10:30:00+00"
         assert template["alias"] == "welcome"
 
         template = templates["data"][1]
@@ -208,8 +208,8 @@ def test_templates_list(self) -> None:
         assert template["name"] == "goodbye-email"
         assert template["status"] == "draft"
         assert template["published_at"] is None
-        assert template["created_at"] == "2024-01-16T10:30:00.000Z"
-        assert template["updated_at"] == "2024-01-16T10:30:00.000Z"
+        assert template["created_at"] == "2024-01-16 10:30:00+00"
+        assert template["updated_at"] == "2024-01-16 10:30:00+00"
         assert template["alias"] == "goodbye"
 
     def test_templates_list_with_pagination_params(self) -> None:
@@ -222,9 +222,9 @@ def test_templates_list_with_pagination_params(self) -> None:
                         "id": "template-1",
                         "name": "welcome-email",
                         "status": "published",
-                        "published_at": "2024-01-15T11:00:00.000Z",
-                        "created_at": "2024-01-15T10:30:00.000Z",
-                        "updated_at": "2024-01-15T10:30:00.000Z",
+                        "published_at": "2024-01-15 11:00:00+00",
+                        "created_at": "2024-01-15 10:30:00+00",
+                        "updated_at": "2024-01-15 10:30:00+00",
                         "alias": "welcome",
                     }
                 ],
@@ -252,8 +252,8 @@ def test_templates_list_with_before_param(self) -> None:
                         "name": "password-reset",
                         "status": "draft",
                         "published_at": None,
-                        "created_at": "2024-01-14T10:30:00.000Z",
-                        "updated_at": "2024-01-14T10:30:00.000Z",
+                        "created_at": "2024-01-14 10:30:00+00",
+                        "updated_at": "2024-01-14 10:30:00+00",
                         "alias": "password-reset",
                     }
                 ],
diff --git a/tests/topics_async_test.py b/tests/topics_async_test.py
index 073662e..9ea0d88 100644
--- a/tests/topics_async_test.py
+++ b/tests/topics_async_test.py
@@ -42,7 +42,7 @@ async def test_topics_get_async(self) -> None:
                 "name": "Weekly Newsletter",
                 "description": "Weekly newsletter for our subscribers",
                 "default_subscription": "opt_in",
-                "created_at": "2023-04-08T00:11:13.110779+00:00",
+                "created_at": "2023-04-08 00:11:13.110779+00",
             }
         )
 
@@ -121,7 +121,7 @@ async def test_topics_list_async(self) -> None:
                         "name": "Weekly Newsletter",
                         "description": "Weekly newsletter for our subscribers",
                         "default_subscription": "opt_in",
-                        "created_at": "2023-04-08T00:11:13.110779+00:00",
+                        "created_at": "2023-04-08 00:11:13.110779+00",
                     }
                 ],
             }
diff --git a/tests/topics_test.py b/tests/topics_test.py
index 7c0dc96..8099c85 100644
--- a/tests/topics_test.py
+++ b/tests/topics_test.py
@@ -51,7 +51,7 @@ def test_topics_get(self) -> None:
                 "name": "Weekly Newsletter",
                 "description": "Weekly newsletter for our subscribers",
                 "default_subscription": "opt_in",
-                "created_at": "2023-04-08T00:11:13.110779+00:00",
+                "created_at": "2023-04-08 00:11:13.110779+00",
             }
         )
 
@@ -60,7 +60,7 @@ def test_topics_get(self) -> None:
         assert topic["name"] == "Weekly Newsletter"
         assert topic["description"] == "Weekly newsletter for our subscribers"
         assert topic["default_subscription"] == "opt_in"
-        assert topic["created_at"] == "2023-04-08T00:11:13.110779+00:00"
+        assert topic["created_at"] == "2023-04-08 00:11:13.110779+00"
 
     def test_should_get_topics_raise_exception_when_no_content(self) -> None:
         self.set_mock_json(None)
@@ -155,7 +155,7 @@ def test_topics_list(self) -> None:
                         "name": "Weekly Newsletter",
                         "description": "Weekly newsletter for our subscribers",
                         "default_subscription": "opt_in",
-                        "created_at": "2023-04-08T00:11:13.110779+00:00",
+                        "created_at": "2023-04-08 00:11:13.110779+00",
                     }
                 ],
             }
@@ -187,14 +187,14 @@ def test_topics_list_with_pagination_params(self) -> None:
                         "name": "First Topic",
                         "description": "First topic description",
                         "default_subscription": "opt_in",
-                        "created_at": "2023-04-08T00:11:13.110779+00:00",
+                        "created_at": "2023-04-08 00:11:13.110779+00",
                     },
                     {
                         "id": "topic-2",
                         "name": "Second Topic",
                         "description": "Second topic description",
                         "default_subscription": "opt_out",
-                        "created_at": "2023-04-09T00:11:13.110779+00:00",
+                        "created_at": "2023-04-09 00:11:13.110779+00",
                     },
                 ],
             }
@@ -222,7 +222,7 @@ def test_topics_list_with_before_param(self) -> None:
                         "name": "Third Topic",
                         "description": "Third topic description",
                         "default_subscription": "opt_in",
-                        "created_at": "2023-04-07T00:11:13.110779+00:00",
+                        "created_at": "2023-04-07 00:11:13.110779+00",
                     }
                 ],
             }
diff --git a/tests/webhooks_async_test.py b/tests/webhooks_async_test.py
index 84b0516..4109caf 100644
--- a/tests/webhooks_async_test.py
+++ b/tests/webhooks_async_test.py
@@ -43,7 +43,7 @@ async def test_webhooks_get_async(self) -> None:
             {
                 "id": "wh_123",
                 "object": "webhook",
-                "created_at": "2024-01-01T00:00:00Z",
+                "created_at": "2024-01-01 00:00:00+00",
                 "status": "enabled",
                 "endpoint": "https://example.com/webhook",
                 "events": ["email.sent"],
@@ -93,7 +93,7 @@ async def test_webhooks_list_async(self) -> None:
                     {
                         "id": "wh_123",
                         "object": "webhook",
-                        "created_at": "2024-01-01T00:00:00Z",
+                        "created_at": "2024-01-01 00:00:00+00",
                         "status": "enabled",
                         "endpoint": "https://example.com/webhook",
                         "events": ["email.sent"],
diff --git a/tests/webhooks_test.py b/tests/webhooks_test.py
index 45fbe73..f82ec20 100644
--- a/tests/webhooks_test.py
+++ b/tests/webhooks_test.py
@@ -32,7 +32,7 @@ def test_webhooks_get(self) -> None:
         webhook_response = {
             "id": "wh_123",
             "object": "webhook",
-            "created_at": "2024-01-01T00:00:00Z",
+            "created_at": "2024-01-01 00:00:00+00",
             "status": "enabled",
             "endpoint": "https://example.com/webhook",
             "events": ["email.sent"],
@@ -65,7 +65,7 @@ def test_webhooks_list(self) -> None:
                 {
                     "id": "wh_123",
                     "object": "webhook",
-                    "created_at": "2024-01-01T00:00:00Z",
+                    "created_at": "2024-01-01 00:00:00+00",
                     "status": "enabled",
                     "endpoint": "https://example.com/webhook",
                     "events": ["email.sent"],
@@ -119,7 +119,7 @@ def test_verify_valid_webhook(self) -> None:
             '{"type":"email.sent","created_at":"2026-02-22T23:41:12.126Z",'
             '"data":{"email_id":"123","message_id":"<111@example.com>",'
             '"from":"Acme <onboarding@resend.dev>","to":["delivered@resend.dev"],'
-            '"subject":"Hello","created_at":"2026-02-22T23:41:11.894719+00:00"}}'
+            '"subject":"Hello","created_at":"2026-02-22T23:41:11.894Z"}}'
         )
 
         signature = self._generate_test_signature(secret, msg_id, timestamp, payload)
@@ -299,7 +299,7 @@ def test_verify_returns_received_email_payload(self) -> None:
         timestamp = str(int(time.time()))
         payload = (
             '{"type":"email.received","created_at":"2026-02-22T23:41:12.126Z",'
-            '"data":{"email_id":"567","created_at":"2026-02-22T23:41:11.894719+00:00",'
+            '"data":{"email_id":"567","created_at":"2026-02-22T23:41:11.894Z",'
             '"from":"onboarding@resend.dev","to":["delivered@resend.dev"],'
             '"bcc":[],"cc":[],"received_for":["forwarded@example.com"],'
             '"message_id":"<111-222-333@email.example.com>",'
@@ -331,7 +331,7 @@ def test_verify_returns_bounced_payload(self) -> None:
             '{"type":"email.bounced","created_at":"2026-02-22T23:41:12.126Z",'
             '"data":{"email_id":"123","message_id":"<111@example.com>",'
             '"from":"Acme <onboarding@resend.dev>","to":["bounced@resend.dev"],'
-            '"subject":"Hello","created_at":"2026-02-22T23:41:11.894719+00:00",'
+            '"subject":"Hello","created_at":"2026-02-22T23:41:11.894Z",'
             '"bounce":{"diagnosticCode":"smtp; 550 5.1.1 user unknown",'
             '"message":"The recipient does not exist.",'
             '"subType":"General","type":"Permanent"}}}'