Python: Fix: AgentRunResponse.created_at returns local datetime labeled as UTC (#2590)

* Initial plan

* Fix created_at to use UTC datetime and add unit tests

Co-authored-by: moonbox3 <35585003+moonbox3@users.noreply.github.com>

* Address code review feedback: move datetime imports to top of test files

Co-authored-by: moonbox3 <35585003+moonbox3@users.noreply.github.com>

* Add UTC timestamp test for OpenAIResponsesClient._create_response_content

Co-authored-by: moonbox3 <35585003+moonbox3@users.noreply.github.com>

* Fix lint issue

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: moonbox3 <35585003+moonbox3@users.noreply.github.com>
Co-authored-by: Evan Mattson <evan.mattson@microsoft.com>

python/packages/core/agent_framework/_workflows/_agent.py

@@ -5,7 +5,7 @@ import logging
 import uuid
 from collections.abc import AsyncIterable
 from dataclasses import dataclass
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import TYPE_CHECKING, Any, ClassVar, TypedDict, cast
 
 from agent_framework import (
@@ -269,7 +269,7 @@ class WorkflowAgent(BaseAgent):
                     author_name=self.name,
                     response_id=response_id,
                     message_id=str(uuid.uuid4()),
-                    created_at=datetime.now().strftime("%Y-%m-%dT%H:%M:%S.%fZ"),
+                    created_at=datetime.now(tz=timezone.utc).strftime("%Y-%m-%dT%H:%M:%S.%fZ"),
                 )
             case _:
                 # Ignore workflow-internal events

python/packages/core/agent_framework/openai/_chat_client.py

@@ -3,7 +3,7 @@
 import json
 import sys
 from collections.abc import AsyncIterable, Awaitable, Callable, Mapping, MutableMapping, MutableSequence, Sequence
-from datetime import datetime
+from datetime import datetime, timezone
 from itertools import chain
 from typing import Any, TypeVar
 
@@ -214,7 +214,7 @@ class OpenAIBaseChatClient(OpenAIBase, BaseChatClient):
             messages.append(ChatMessage(role="assistant", contents=contents))
         return ChatResponse(
             response_id=response.id,
-            created_at=datetime.fromtimestamp(response.created).strftime("%Y-%m-%dT%H:%M:%S.%fZ"),
+            created_at=datetime.fromtimestamp(response.created, tz=timezone.utc).strftime("%Y-%m-%dT%H:%M:%S.%fZ"),
             usage_details=self._usage_details_from_openai(response.usage) if response.usage else None,
             messages=messages,
             model_id=response.model,
@@ -249,7 +249,7 @@ class OpenAIBaseChatClient(OpenAIBase, BaseChatClient):
             if text_content := self._parse_text_from_choice(choice):
                 contents.append(text_content)
         return ChatResponseUpdate(
-            created_at=datetime.fromtimestamp(chunk.created).strftime("%Y-%m-%dT%H:%M:%S.%fZ"),
+            created_at=datetime.fromtimestamp(chunk.created, tz=timezone.utc).strftime("%Y-%m-%dT%H:%M:%S.%fZ"),
             contents=contents,
             role=Role.ASSISTANT,
             model_id=chunk.model,

python/packages/core/agent_framework/openai/_responses_client.py

@@ -1,7 +1,7 @@
 # Copyright (c) Microsoft. All rights reserved.
 
 from collections.abc import AsyncIterable, Awaitable, Callable, Mapping, MutableMapping, MutableSequence, Sequence
-from datetime import datetime
+from datetime import datetime, timezone
 from itertools import chain
 from typing import Any, TypeVar
 
@@ -815,7 +815,9 @@ class OpenAIBaseResponsesClient(OpenAIBase, BaseChatClient):
         response_message = ChatMessage(role="assistant", contents=contents)
         args: dict[str, Any] = {
             "response_id": response.id,
-            "created_at": datetime.fromtimestamp(response.created_at).strftime("%Y-%m-%dT%H:%M:%S.%fZ"),
+            "created_at": datetime.fromtimestamp(response.created_at, tz=timezone.utc).strftime(
+                "%Y-%m-%dT%H:%M:%S.%fZ"
+            ),
             "messages": response_message,
             "model_id": response.model,
             "additional_properties": metadata,

python/packages/core/tests/core/test_types.py

@@ -2,6 +2,7 @@
 
 import base64
 from collections.abc import AsyncIterable
+from datetime import datetime, timezone
 from typing import Any
 
 import pytest
@@ -936,6 +937,52 @@ def test_agent_run_response_update_str_method(text_content: TextContent) -> None
     assert str(update) == "Test content"
 
 
+def test_agent_run_response_update_created_at() -> None:
+    """Test that AgentRunResponseUpdate properly handles created_at timestamps."""
+    # Test with a properly formatted UTC timestamp
+    utc_timestamp = "2024-12-01T00:31:30.000000Z"
+    update = AgentRunResponseUpdate(
+        contents=[TextContent(text="test")],
+        role=Role.ASSISTANT,
+        created_at=utc_timestamp,
+    )
+    assert update.created_at == utc_timestamp
+    assert update.created_at.endswith("Z"), "Timestamp should end with 'Z' for UTC"
+
+    # Verify that we can generate a proper UTC timestamp
+    now_utc = datetime.now(tz=timezone.utc)
+    formatted_utc = now_utc.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
+    update_with_now = AgentRunResponseUpdate(
+        contents=[TextContent(text="test")],
+        role=Role.ASSISTANT,
+        created_at=formatted_utc,
+    )
+    assert update_with_now.created_at == formatted_utc
+    assert update_with_now.created_at.endswith("Z")
+
+
+def test_agent_run_response_created_at() -> None:
+    """Test that AgentRunResponse properly handles created_at timestamps."""
+    # Test with a properly formatted UTC timestamp
+    utc_timestamp = "2024-12-01T00:31:30.000000Z"
+    response = AgentRunResponse(
+        messages=[ChatMessage(role=Role.ASSISTANT, text="Hello")],
+        created_at=utc_timestamp,
+    )
+    assert response.created_at == utc_timestamp
+    assert response.created_at.endswith("Z"), "Timestamp should end with 'Z' for UTC"
+
+    # Verify that we can generate a proper UTC timestamp
+    now_utc = datetime.now(tz=timezone.utc)
+    formatted_utc = now_utc.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
+    response_with_now = AgentRunResponse(
+        messages=[ChatMessage(role=Role.ASSISTANT, text="Hello")],
+        created_at=formatted_utc,
+    )
+    assert response_with_now.created_at == formatted_utc
+    assert response_with_now.created_at.endswith("Z")
+
+
 # region ErrorContent
 
 

python/packages/core/tests/openai/test_openai_chat_client_base.py

@@ -1,6 +1,7 @@
 # Copyright (c) Microsoft. All rights reserved.
 
 from copy import deepcopy
+from datetime import datetime, timezone
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
@@ -370,3 +371,75 @@ async def test_get_streaming_no_stream(
                 messages=chat_history,
             )
         ]
+
+
+# region UTC Timestamp Tests
+
+
+def test_chat_response_created_at_uses_utc(openai_unit_test_env: dict[str, str]):
+    """Test that ChatResponse.created_at uses UTC timestamp, not local time.
+
+    This is a regression test for the issue where created_at was using local time
+    but labeling it as UTC (with 'Z' suffix).
+    """
+    from agent_framework import ChatOptions
+
+    # Use a specific Unix timestamp: 1733011890 = 2024-12-01T00:31:30Z (UTC)
+    # This ensures we test that the timestamp is actually converted to UTC
+    utc_timestamp = 1733011890
+
+    mock_response = ChatCompletion(
+        id="test_id",
+        choices=[
+            Choice(index=0, message=ChatCompletionMessage(content="test", role="assistant"), finish_reason="stop")
+        ],
+        created=utc_timestamp,
+        model="test",
+        object="chat.completion",
+    )
+
+    client = OpenAIChatClient()
+    response = client._create_chat_response(mock_response, ChatOptions())
+
+    # Verify that created_at is correctly formatted as UTC
+    assert response.created_at is not None
+    assert response.created_at.endswith("Z"), "Timestamp should end with 'Z' for UTC"
+
+    # Parse the timestamp and verify it matches UTC time
+    expected_utc_time = datetime.fromtimestamp(utc_timestamp, tz=timezone.utc)
+    expected_formatted = expected_utc_time.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
+    assert response.created_at == expected_formatted, (
+        f"Expected UTC timestamp {expected_formatted}, got {response.created_at}"
+    )
+
+
+def test_chat_response_update_created_at_uses_utc(openai_unit_test_env: dict[str, str]):
+    """Test that ChatResponseUpdate.created_at uses UTC timestamp, not local time.
+
+    This is a regression test for the issue where created_at was using local time
+    but labeling it as UTC (with 'Z' suffix).
+    """
+    # Use a specific Unix timestamp: 1733011890 = 2024-12-01T00:31:30Z (UTC)
+    utc_timestamp = 1733011890
+
+    mock_chunk = ChatCompletionChunk(
+        id="test_id",
+        choices=[ChunkChoice(index=0, delta=ChunkChoiceDelta(content="test", role="assistant"), finish_reason="stop")],
+        created=utc_timestamp,
+        model="test",
+        object="chat.completion.chunk",
+    )
+
+    client = OpenAIChatClient()
+    response_update = client._create_chat_response_update(mock_chunk)
+
+    # Verify that created_at is correctly formatted as UTC
+    assert response_update.created_at is not None
+    assert response_update.created_at.endswith("Z"), "Timestamp should end with 'Z' for UTC"
+
+    # Parse the timestamp and verify it matches UTC time
+    expected_utc_time = datetime.fromtimestamp(utc_timestamp, tz=timezone.utc)
+    expected_formatted = expected_utc_time.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
+    assert response_update.created_at == expected_formatted, (
+        f"Expected UTC timestamp {expected_formatted}, got {response_update.created_at}"
+    )

python/packages/core/tests/openai/test_openai_responses_client.py

@@ -3,6 +3,7 @@
 import asyncio
 import base64
 import os
+from datetime import datetime, timezone
 from typing import Annotated
 from unittest.mock import MagicMock, patch
 
@@ -684,6 +685,51 @@ def test_create_response_content_with_mcp_approval_request() -> None:
     assert req.function_call.additional_properties["server_label"] == "My_MCP"
 
 
+def test_responses_client_created_at_uses_utc(openai_unit_test_env: dict[str, str]) -> None:
+    """Test that ChatResponse from responses client uses UTC timestamp.
+
+    This is a regression test for the issue where created_at was using local time
+    but labeling it as UTC (with 'Z' suffix).
+    """
+    client = OpenAIResponsesClient()
+
+    # Use a specific Unix timestamp: 1733011890 = 2024-12-01T00:31:30Z (UTC)
+    utc_timestamp = 1733011890
+
+    mock_response = MagicMock()
+    mock_response.output_parsed = None
+    mock_response.metadata = {}
+    mock_response.usage = None
+    mock_response.id = "test-id"
+    mock_response.model = "test-model"
+    mock_response.created_at = utc_timestamp
+
+    mock_message_content = MagicMock()
+    mock_message_content.type = "output_text"
+    mock_message_content.text = "Test response"
+    mock_message_content.annotations = None
+
+    mock_message_item = MagicMock()
+    mock_message_item.type = "message"
+    mock_message_item.content = [mock_message_content]
+
+    mock_response.output = [mock_message_item]
+
+    with patch.object(client, "_get_metadata_from_response", return_value={}):
+        response = client._create_response_content(mock_response, chat_options=ChatOptions())  # type: ignore
+
+    # Verify that created_at is correctly formatted as UTC
+    assert response.created_at is not None
+    assert response.created_at.endswith("Z"), "Timestamp should end with 'Z' for UTC"
+
+    # Parse the timestamp and verify it matches UTC time
+    expected_utc_time = datetime.fromtimestamp(utc_timestamp, tz=timezone.utc)
+    expected_formatted = expected_utc_time.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
+    assert response.created_at == expected_formatted, (
+        f"Expected UTC timestamp {expected_formatted}, got {response.created_at}"
+    )
+
+
 def test_tools_to_response_tools_with_raw_image_generation() -> None:
     """Test that raw image_generation tool dict is handled correctly with parameter mapping."""
     client = OpenAIResponsesClient(model_id="test-model", api_key="test-key")