From c65c959d15e241ef71cdc80b9a75be2a2e5c74db Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 24 Feb 2026 19:06:26 +0000
Subject: [PATCH 1/4] Initial plan


From 44aca2e1b266adc099ca97cfc70253c93b8df4f8 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 24 Feb 2026 19:15:34 +0000
Subject: [PATCH 2/4] Add start_time and end_time parameters to OpenTelemetry
 scope classes

This change implements support for custom start and end times on OpenTelemetry spans,
mirroring the Node.js PR #205. Changes include:

- Add TimeInput type alias supporting int (nanoseconds), float (seconds), tuple (HrTime), and datetime
- Update OpenTelemetryScope base class with start_time and end_time constructor parameters
- Add set_end_time() method for setting end time after construction
- Update InferenceScope, InvokeAgentScope, ExecuteToolScope, and OutputScope to forward parameters
- Add comprehensive unit tests for custom start/end time functionality

Co-authored-by: nikhilNava <211831449+nikhilNava@users.noreply.github.com>
---
 .../observability/core/__init__.py            |   4 +-
 .../observability/core/execute_tool_scope.py  |  22 +-
 .../observability/core/inference_scope.py     |  16 +-
 .../observability/core/invoke_agent_scope.py  |  20 +-
 .../observability/core/opentelemetry_scope.py | 104 ++++++-
 .../core/spans_scopes/output_scope.py         |  14 +-
 .../core/test_custom_start_end_time.py        | 253 ++++++++++++++++++
 7 files changed, 421 insertions(+), 12 deletions(-)
 create mode 100644 tests/observability/core/test_custom_start_end_time.py

diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/__init__.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/__init__.py
index e19cf8e9..47245187 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/__init__.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/__init__.py
@@ -24,7 +24,7 @@
 from .invoke_agent_details import InvokeAgentDetails
 from .invoke_agent_scope import InvokeAgentScope
 from .middleware.baggage_builder import BaggageBuilder
-from .opentelemetry_scope import OpenTelemetryScope
+from .opentelemetry_scope import OpenTelemetryScope, TimeInput
 from .request import Request
 from .source_metadata import SourceMetadata
 from .tenant_details import TenantDetails
@@ -47,6 +47,8 @@
     "SpanProcessor",
     # Base scope class
     "OpenTelemetryScope",
+    # Type aliases
+    "TimeInput",
     # Specific scope classes
     "ExecuteToolScope",
     "InvokeAgentScope",
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py
index f502cee0..6a5ab8d2 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py
@@ -15,7 +15,7 @@
     SERVER_ADDRESS_KEY,
     SERVER_PORT_KEY,
 )
-from .opentelemetry_scope import OpenTelemetryScope
+from .opentelemetry_scope import OpenTelemetryScope, TimeInput
 from .request import Request
 from .tenant_details import TenantDetails
 from .tool_call_details import ToolCallDetails
@@ -31,6 +31,8 @@ def start(
         tenant_details: TenantDetails,
         request: Request | None = None,
         parent_id: str | None = None,
+        start_time: TimeInput = None,
+        end_time: TimeInput = None,
     ) -> "ExecuteToolScope":
         """Creates and starts a new scope for tool execution tracing.
 
@@ -41,11 +43,18 @@ def start(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
+            start_time: Optional explicit start time (ms epoch, Date, or HrTime). Useful when
+                recording a tool call after execution has already completed.
+            end_time: Optional explicit end time (ms epoch, Date, or HrTime). When provided,
+                the span will use this timestamp when disposed instead of the current
+                wall-clock time.
 
         Returns:
             A new ExecuteToolScope instance
         """
-        return ExecuteToolScope(details, agent_details, tenant_details, request, parent_id)
+        return ExecuteToolScope(
+            details, agent_details, tenant_details, request, parent_id, start_time, end_time
+        )
 
     def __init__(
         self,
@@ -54,6 +63,8 @@ def __init__(
         tenant_details: TenantDetails,
         request: Request | None = None,
         parent_id: str | None = None,
+        start_time: TimeInput = None,
+        end_time: TimeInput = None,
     ):
         """Initialize the tool execution scope.
 
@@ -64,6 +75,11 @@ def __init__(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
+            start_time: Optional explicit start time (ms epoch, Date, or HrTime). Useful when
+                recording a tool call after execution has already completed.
+            end_time: Optional explicit end time (ms epoch, Date, or HrTime). When provided,
+                the span will use this timestamp when disposed instead of the current
+                wall-clock time.
         """
         super().__init__(
             kind="Internal",
@@ -72,6 +88,8 @@ def __init__(
             agent_details=agent_details,
             tenant_details=tenant_details,
             parent_id=parent_id,
+            start_time=start_time,
+            end_time=end_time,
         )
 
         # Extract details using deconstruction-like approach
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py
index 79294ea6..df7fc1db 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py
@@ -19,7 +19,7 @@
     GEN_AI_USAGE_OUTPUT_TOKENS_KEY,
 )
 from .inference_call_details import InferenceCallDetails
-from .opentelemetry_scope import OpenTelemetryScope
+from .opentelemetry_scope import OpenTelemetryScope, TimeInput
 from .request import Request
 from .tenant_details import TenantDetails
 from .utils import safe_json_dumps
@@ -35,6 +35,8 @@ def start(
         tenant_details: TenantDetails,
         request: Request | None = None,
         parent_id: str | None = None,
+        start_time: TimeInput = None,
+        end_time: TimeInput = None,
     ) -> "InferenceScope":
         """Creates and starts a new scope for inference tracing.
 
@@ -45,11 +47,15 @@ def start(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
+            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
+            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
 
         Returns:
             A new InferenceScope instance
         """
-        return InferenceScope(details, agent_details, tenant_details, request, parent_id)
+        return InferenceScope(
+            details, agent_details, tenant_details, request, parent_id, start_time, end_time
+        )
 
     def __init__(
         self,
@@ -58,6 +64,8 @@ def __init__(
         tenant_details: TenantDetails,
         request: Request | None = None,
         parent_id: str | None = None,
+        start_time: TimeInput = None,
+        end_time: TimeInput = None,
     ):
         """Initialize the inference scope.
 
@@ -68,6 +76,8 @@ def __init__(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
+            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
+            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
         """
 
         super().__init__(
@@ -77,6 +87,8 @@ def __init__(
             agent_details=agent_details,
             tenant_details=tenant_details,
             parent_id=parent_id,
+            start_time=start_time,
+            end_time=end_time,
         )
 
         if request:
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py
index f9bf82ee..df08bf21 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py
@@ -32,7 +32,7 @@
 )
 from .invoke_agent_details import InvokeAgentDetails
 from .models.caller_details import CallerDetails
-from .opentelemetry_scope import OpenTelemetryScope
+from .opentelemetry_scope import OpenTelemetryScope, TimeInput
 from .request import Request
 from .tenant_details import TenantDetails
 from .utils import safe_json_dumps, validate_and_normalize_ip
@@ -50,6 +50,8 @@ def start(
         request: Request | None = None,
         caller_agent_details: AgentDetails | None = None,
         caller_details: CallerDetails | None = None,
+        start_time: TimeInput = None,
+        end_time: TimeInput = None,
     ) -> "InvokeAgentScope":
         """Create and start a new scope for agent invocation tracing.
 
@@ -60,12 +62,20 @@ def start(
             request: Optional request details for additional context
             caller_agent_details: Optional details of the caller agent
             caller_details: Optional details of the non-agentic caller
+            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
+            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
 
         Returns:
             A new InvokeAgentScope instance
         """
         return InvokeAgentScope(
-            invoke_agent_details, tenant_details, request, caller_agent_details, caller_details
+            invoke_agent_details,
+            tenant_details,
+            request,
+            caller_agent_details,
+            caller_details,
+            start_time,
+            end_time,
         )
 
     def __init__(
@@ -75,6 +85,8 @@ def __init__(
         request: Request | None = None,
         caller_agent_details: AgentDetails | None = None,
         caller_details: CallerDetails | None = None,
+        start_time: TimeInput = None,
+        end_time: TimeInput = None,
     ):
         """Initialize the agent invocation scope.
 
@@ -84,6 +96,8 @@ def __init__(
             request: Optional request details for additional context
             caller_agent_details: Optional details of the caller agent
             caller_details: Optional details of the non-agentic caller
+            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
+            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
         """
         activity_name = INVOKE_AGENT_OPERATION_NAME
         if invoke_agent_details.details.agent_name:
@@ -97,6 +111,8 @@ def __init__(
             activity_name=activity_name,
             agent_details=invoke_agent_details.details,
             tenant_details=tenant_details,
+            start_time=start_time,
+            end_time=end_time,
         )
 
         endpoint, _, session_id = (
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py
index 90b3e84b..55066934 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py
@@ -6,6 +6,7 @@
 import logging
 import os
 import time
+from datetime import datetime
 from threading import Lock
 from typing import TYPE_CHECKING, Any
 
@@ -48,6 +49,12 @@
 # Create logger for this module - inherits from 'microsoft_agents_a365.observability.core'
 logger = logging.getLogger(__name__)
 
+# TimeInput is a type alias for types that can be used as span timestamps.
+# OpenTelemetry Python SDK accepts int (nanoseconds since epoch), float (seconds since epoch),
+# or a tuple of (seconds, nanoseconds) as HrTime.
+# We extend this to also accept datetime objects for convenience.
+TimeInput = int | float | tuple[int, int] | datetime | None
+
 
 class OpenTelemetryScope:
     """Base class for OpenTelemetry tracing scopes in the SDK."""
@@ -80,6 +87,8 @@ def __init__(
         agent_details: "AgentDetails | None" = None,
         tenant_details: "TenantDetails | None" = None,
         parent_id: str | None = None,
+        start_time: TimeInput = None,
+        end_time: TimeInput = None,
     ):
         """Initialize the OpenTelemetry scope.
 
@@ -91,9 +100,20 @@ def __init__(
             tenant_details: Optional tenant details
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
+            start_time: Optional explicit start time. Can be:
+                - int: nanoseconds since epoch
+                - float: seconds since epoch
+                - tuple[int, int]: HrTime as (seconds, nanoseconds)
+                - datetime: Python datetime object
+                Useful when recording an operation after it has already completed.
+            end_time: Optional explicit end time in the same format as start_time.
+                When provided, the span will use this timestamp when disposed
+                instead of the current wall-clock time.
         """
         self._span: Span | None = None
-        self._start_time = time.time()
+        self._wall_clock_start_ms = time.time() * 1000  # milliseconds
+        self._custom_start_time: TimeInput = start_time
+        self._custom_end_time: TimeInput = end_time
         self._has_ended = False
         self._error_type: str | None = None
         self._exception: Exception | None = None
@@ -119,7 +139,15 @@ def __init__(
             parent_context = parse_parent_id_to_context(parent_id)
             span_context = parent_context if parent_context else context.get_current()
 
-            self._span = tracer.start_span(activity_name, kind=activity_kind, context=span_context)
+            # Convert custom start time to OTel-compatible format (nanoseconds since epoch)
+            otel_start_time = self._time_input_to_ns(start_time) if start_time else None
+
+            self._span = tracer.start_span(
+                activity_name,
+                kind=activity_kind,
+                context=span_context,
+                start_time=otel_start_time,
+            )
 
             # Log span creation
             if self._span:
@@ -230,6 +258,71 @@ def record_attributes(self, attributes: dict[str, Any] | list[tuple[str, Any]])
             if key and key.strip():
                 self._span.set_attribute(key, value)
 
+    @staticmethod
+    def _time_input_to_ns(t: TimeInput) -> int | None:
+        """Convert a TimeInput value to nanoseconds since epoch.
+
+        OpenTelemetry Python SDK accepts int (nanoseconds since epoch) for span
+        start_time and end_time parameters.
+
+        Args:
+            t: TimeInput value which can be:
+                - int: nanoseconds since epoch (returned as-is)
+                - float: seconds since epoch
+                - tuple[int, int]: HrTime as (seconds, nanoseconds)
+                - datetime: Python datetime object
+
+        Returns:
+            Nanoseconds since epoch, or None if input is None
+        """
+        if t is None:
+            return None
+        if isinstance(t, int):
+            # Assume nanoseconds if it's an integer
+            return t
+        if isinstance(t, float):
+            # Convert seconds to nanoseconds
+            return int(t * 1_000_000_000)
+        if isinstance(t, tuple) and len(t) == 2:
+            # HrTime: (seconds, nanoseconds)
+            seconds, nanos = t
+            return seconds * 1_000_000_000 + nanos
+        if isinstance(t, datetime):
+            return int(t.timestamp() * 1_000_000_000)
+        logger.warning(
+            f"_time_input_to_ns received unexpected TimeInput "
+            f"(type={type(t).__name__}); returning None"
+        )
+        return None
+
+    @staticmethod
+    def _time_input_to_ms(t: TimeInput) -> float | None:
+        """Convert a TimeInput value to milliseconds since epoch.
+
+        Used for duration calculations.
+
+        Args:
+            t: TimeInput value (see _time_input_to_ns for accepted types)
+
+        Returns:
+            Milliseconds since epoch, or None if input is None
+        """
+        ns = OpenTelemetryScope._time_input_to_ns(t)
+        return ns / 1_000_000 if ns is not None else None
+
+    def set_end_time(self, end_time: TimeInput) -> None:
+        """Set a custom end time for the scope.
+
+        When set, dispose() will pass this value to span.end() instead of using
+        the current wall-clock time. This is useful when the actual end time of
+        the operation is known before the scope is disposed.
+
+        Args:
+            end_time: The end time as nanoseconds since epoch, seconds since epoch,
+                     HrTime tuple (seconds, nanoseconds), or datetime object.
+        """
+        self._custom_end_time = end_time
+
     def _end(self) -> None:
         """End the span and record metrics."""
         if self._span and self._is_telemetry_enabled() and not self._has_ended:
@@ -237,7 +330,12 @@ def _end(self) -> None:
             span_id = f"{self._span.context.span_id:016x}" if self._span.context else "unknown"
             logger.info(f"Span ended: '{self._span.name}' ({span_id})")
 
-            self._span.end()
+            # Convert custom end time to OTel-compatible format (nanoseconds since epoch)
+            otel_end_time = self._time_input_to_ns(self._custom_end_time)
+            if otel_end_time is not None:
+                self._span.end(end_time=otel_end_time)
+            else:
+                self._span.end()
 
     def __enter__(self):
         """Enter the context manager and make span active."""
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/spans_scopes/output_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/spans_scopes/output_scope.py
index 6f01c42c..4f526058 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/spans_scopes/output_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/spans_scopes/output_scope.py
@@ -4,7 +4,7 @@
 from ..agent_details import AgentDetails
 from ..constants import GEN_AI_OUTPUT_MESSAGES_KEY
 from ..models.response import Response
-from ..opentelemetry_scope import OpenTelemetryScope
+from ..opentelemetry_scope import OpenTelemetryScope, TimeInput
 from ..tenant_details import TenantDetails
 from ..utils import safe_json_dumps
 
@@ -20,6 +20,8 @@ def start(
         tenant_details: TenantDetails,
         response: Response,
         parent_id: str | None = None,
+        start_time: TimeInput = None,
+        end_time: TimeInput = None,
     ) -> "OutputScope":
         """Creates and starts a new scope for output tracing.
 
@@ -29,11 +31,13 @@ def start(
             response: The response details from the agent
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
+            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
+            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
 
         Returns:
             A new OutputScope instance
         """
-        return OutputScope(agent_details, tenant_details, response, parent_id)
+        return OutputScope(agent_details, tenant_details, response, parent_id, start_time, end_time)
 
     def __init__(
         self,
@@ -41,6 +45,8 @@ def __init__(
         tenant_details: TenantDetails,
         response: Response,
         parent_id: str | None = None,
+        start_time: TimeInput = None,
+        end_time: TimeInput = None,
     ):
         """Initialize the output scope.
 
@@ -50,6 +56,8 @@ def __init__(
             response: The response details from the agent
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
+            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
+            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
         """
         super().__init__(
             kind="Client",
@@ -58,6 +66,8 @@ def __init__(
             agent_details=agent_details,
             tenant_details=tenant_details,
             parent_id=parent_id,
+            start_time=start_time,
+            end_time=end_time,
         )
 
         # Initialize accumulated messages list
diff --git a/tests/observability/core/test_custom_start_end_time.py b/tests/observability/core/test_custom_start_end_time.py
new file mode 100644
index 00000000..cb824c02
--- /dev/null
+++ b/tests/observability/core/test_custom_start_end_time.py
@@ -0,0 +1,253 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+"""Tests for custom start and end time support on OpenTelemetry scopes."""
+
+import os
+import sys
+import unittest
+from datetime import UTC, datetime
+from pathlib import Path
+
+import pytest
+from microsoft_agents_a365.observability.core import (
+    AgentDetails,
+    ExecuteToolScope,
+    TenantDetails,
+    ToolCallDetails,
+    configure,
+    get_tracer_provider,
+)
+from microsoft_agents_a365.observability.core.config import _telemetry_manager
+from microsoft_agents_a365.observability.core.opentelemetry_scope import OpenTelemetryScope
+from opentelemetry.sdk.trace.export import SimpleSpanProcessor
+from opentelemetry.sdk.trace.export.in_memory_span_exporter import InMemorySpanExporter
+
+
+class TestCustomStartEndTime(unittest.TestCase):
+    """Unit tests for custom start and end time support."""
+
+    @classmethod
+    def setUpClass(cls):
+        """Set up test environment once for all tests."""
+        os.environ["ENABLE_A365_OBSERVABILITY"] = "true"
+
+        configure(
+            service_name="test-custom-time-service",
+            service_namespace="test-namespace",
+        )
+        # Create test data
+        cls.tenant_details = TenantDetails(tenant_id="12345678-1234-5678-1234-567812345678")
+        cls.agent_details = AgentDetails(
+            agent_id="test-agent-123",
+            agent_name="Test Agent",
+            agent_description="A test agent for custom time testing",
+        )
+        cls.tool_details = ToolCallDetails(
+            tool_name="test_tool",
+            arguments='{"arg": "value"}',
+            tool_call_id="call-123",
+        )
+
+    def setUp(self):
+        super().setUp()
+
+        # Reset TelemetryManager state to ensure fresh configuration
+        _telemetry_manager._tracer_provider = None
+        _telemetry_manager._span_processors = {}
+        OpenTelemetryScope._tracer = None
+
+        # Reconfigure to get a fresh TracerProvider
+        configure(
+            service_name="test-custom-time-service",
+            service_namespace="test-namespace",
+        )
+
+        # Set up tracer to capture spans
+        self.span_exporter = InMemorySpanExporter()
+        tracer_provider = get_tracer_provider()
+        tracer_provider.add_span_processor(SimpleSpanProcessor(self.span_exporter))
+
+    def tearDown(self):
+        super().tearDown()
+        self.span_exporter.clear()
+
+    def _get_finished_span(self):
+        """Get the last finished span from the exporter."""
+        finished_spans = self.span_exporter.get_finished_spans()
+        self.assertTrue(finished_spans, "Expected at least one span to be created")
+        return finished_spans[-1]
+
+    def test_custom_start_and_end_time_with_nanoseconds(self):
+        """Test that constructor-provided start and end times are recorded on the span."""
+        # Use nanoseconds since epoch
+        custom_start_ns = 1700000000000000000  # 2023-11-14T22:13:20Z
+        custom_end_ns = 1700000005000000000  # 5 seconds later
+
+        scope = ExecuteToolScope.start(
+            self.tool_details,
+            self.agent_details,
+            self.tenant_details,
+            start_time=custom_start_ns,
+            end_time=custom_end_ns,
+        )
+        scope.dispose()
+
+        span = self._get_finished_span()
+
+        # OTel Python SDK stores times as nanoseconds (int)
+        span_start_ns = span.start_time
+        span_end_ns = span.end_time
+
+        # Verify start and end times are close to what we provided
+        self.assertAlmostEqual(span_start_ns, custom_start_ns, delta=1000)  # 1μs tolerance
+        self.assertAlmostEqual(span_end_ns, custom_end_ns, delta=1000)
+
+    def test_custom_start_and_end_time_with_datetime(self):
+        """Test that datetime objects are correctly converted to span timestamps."""
+        custom_start = datetime(2023, 11, 14, 22, 13, 20, tzinfo=UTC)
+        custom_end = datetime(2023, 11, 14, 22, 13, 25, tzinfo=UTC)  # 5 seconds later
+
+        scope = ExecuteToolScope.start(
+            self.tool_details,
+            self.agent_details,
+            self.tenant_details,
+            start_time=custom_start,
+            end_time=custom_end,
+        )
+        scope.dispose()
+
+        span = self._get_finished_span()
+
+        expected_start_ns = int(custom_start.timestamp() * 1_000_000_000)
+        expected_end_ns = int(custom_end.timestamp() * 1_000_000_000)
+
+        span_start_ns = span.start_time
+        span_end_ns = span.end_time
+
+        self.assertAlmostEqual(span_start_ns, expected_start_ns, delta=1000)
+        self.assertAlmostEqual(span_end_ns, expected_end_ns, delta=1000)
+
+    def test_custom_start_and_end_time_with_float_seconds(self):
+        """Test that float seconds are correctly converted to span timestamps."""
+        # Float seconds since epoch
+        custom_start_sec = 1700000000.0  # 2023-11-14T22:13:20Z
+        custom_end_sec = 1700000005.5  # 5.5 seconds later
+
+        scope = ExecuteToolScope.start(
+            self.tool_details,
+            self.agent_details,
+            self.tenant_details,
+            start_time=custom_start_sec,
+            end_time=custom_end_sec,
+        )
+        scope.dispose()
+
+        span = self._get_finished_span()
+
+        expected_start_ns = int(custom_start_sec * 1_000_000_000)
+        expected_end_ns = int(custom_end_sec * 1_000_000_000)
+
+        span_start_ns = span.start_time
+        span_end_ns = span.end_time
+
+        self.assertAlmostEqual(span_start_ns, expected_start_ns, delta=1000)
+        self.assertAlmostEqual(span_end_ns, expected_end_ns, delta=1000)
+
+    def test_custom_start_and_end_time_with_hrtime_tuple(self):
+        """Test that HrTime tuples (seconds, nanoseconds) are correctly handled."""
+        # HrTime: (seconds, nanoseconds)
+        custom_start: tuple[int, int] = (1700000000, 0)  # 2023-11-14T22:13:20Z
+        custom_end: tuple[int, int] = (1700000005, 500000000)  # 5.5 seconds later
+
+        scope = ExecuteToolScope.start(
+            self.tool_details,
+            self.agent_details,
+            self.tenant_details,
+            start_time=custom_start,
+            end_time=custom_end,
+        )
+        scope.dispose()
+
+        span = self._get_finished_span()
+
+        expected_start_ns = custom_start[0] * 1_000_000_000 + custom_start[1]
+        expected_end_ns = custom_end[0] * 1_000_000_000 + custom_end[1]
+
+        span_start_ns = span.start_time
+        span_end_ns = span.end_time
+
+        self.assertAlmostEqual(span_start_ns, expected_start_ns, delta=1000)
+        self.assertAlmostEqual(span_end_ns, expected_end_ns, delta=1000)
+
+    def test_set_end_time_overrides_end_time(self):
+        """Test that set_end_time overrides the end time when called before dispose."""
+        custom_start_ns = 1700000040000000000
+        initial_end_ns = 1700000045000000000  # 5 seconds after start
+        later_end_ns = 1700000048000000000  # 8 seconds after start
+
+        scope = ExecuteToolScope.start(
+            self.tool_details,
+            self.agent_details,
+            self.tenant_details,
+            start_time=custom_start_ns,
+            end_time=initial_end_ns,
+        )
+        # Override the end time
+        scope.set_end_time(later_end_ns)
+        scope.dispose()
+
+        span = self._get_finished_span()
+
+        span_end_ns = span.end_time
+        self.assertAlmostEqual(span_end_ns, later_end_ns, delta=1000)
+
+    def test_wall_clock_time_used_when_no_custom_times(self):
+        """Test that wall-clock time is used when no custom times are provided."""
+        import time
+
+        before = time.time_ns()
+        scope = ExecuteToolScope.start(
+            self.tool_details,
+            self.agent_details,
+            self.tenant_details,
+        )
+        scope.dispose()
+        after = time.time_ns()
+
+        span = self._get_finished_span()
+
+        span_start_ns = span.start_time
+        span_end_ns = span.end_time
+
+        # Span times should be within the before/after window
+        # Allow some tolerance for processing time
+        self.assertGreaterEqual(span_start_ns, before - 1_000_000)  # 1ms tolerance
+        self.assertLessEqual(span_end_ns, after + 1_000_000)
+
+    def test_only_start_time_provided(self):
+        """Test that only custom start time can be provided without end time."""
+        custom_start_ns = 1700000000000000000
+
+        scope = ExecuteToolScope.start(
+            self.tool_details,
+            self.agent_details,
+            self.tenant_details,
+            start_time=custom_start_ns,
+        )
+        scope.dispose()
+
+        span = self._get_finished_span()
+
+        span_start_ns = span.start_time
+
+        # Start time should match what we provided
+        self.assertAlmostEqual(span_start_ns, custom_start_ns, delta=1000)
+
+        # End time should be close to current time (not custom)
+        span_end_ns = span.end_time
+        self.assertGreater(span_end_ns, span_start_ns)
+
+
+if __name__ == "__main__":
+    sys.exit(pytest.main([str(Path(__file__))] + sys.argv[1:]))

From a2f33854e6c4fa9f8799be2cb93084f8b441c7d1 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 24 Feb 2026 19:18:19 +0000
Subject: [PATCH 3/4] Address code review feedback

- Remove unused _wall_clock_start_ms variable
- Fix documentation to accurately describe TimeInput accepted formats
- Remove unused time import

Co-authored-by: nikhilNava <211831449+nikhilNava@users.noreply.github.com>
---
 .../observability/core/execute_tool_scope.py   | 18 ++++++++++--------
 .../observability/core/inference_scope.py      | 10 ++++++----
 .../observability/core/invoke_agent_scope.py   | 10 ++++++----
 .../observability/core/opentelemetry_scope.py  |  2 --
 4 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py
index 6a5ab8d2..8b92e2b0 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py
@@ -43,11 +43,12 @@ def start(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time (ms epoch, Date, or HrTime). Useful when
+            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
+                float (seconds since epoch), tuple[int, int] (HrTime), or datetime. Useful when
                 recording a tool call after execution has already completed.
-            end_time: Optional explicit end time (ms epoch, Date, or HrTime). When provided,
-                the span will use this timestamp when disposed instead of the current
-                wall-clock time.
+            end_time: Optional explicit end time in the same formats as start_time. When
+                provided, the span will use this timestamp when disposed instead of the
+                current wall-clock time.
 
         Returns:
             A new ExecuteToolScope instance
@@ -75,11 +76,12 @@ def __init__(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time (ms epoch, Date, or HrTime). Useful when
+            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
+                float (seconds since epoch), tuple[int, int] (HrTime), or datetime. Useful when
                 recording a tool call after execution has already completed.
-            end_time: Optional explicit end time (ms epoch, Date, or HrTime). When provided,
-                the span will use this timestamp when disposed instead of the current
-                wall-clock time.
+            end_time: Optional explicit end time in the same formats as start_time. When
+                provided, the span will use this timestamp when disposed instead of the
+                current wall-clock time.
         """
         super().__init__(
             kind="Internal",
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py
index df7fc1db..e50863e7 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py
@@ -47,8 +47,9 @@ def start(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
-            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
+            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
+                float (seconds since epoch), tuple[int, int] (HrTime), or datetime.
+            end_time: Optional explicit end time in the same formats as start_time.
 
         Returns:
             A new InferenceScope instance
@@ -76,8 +77,9 @@ def __init__(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
-            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
+            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
+                float (seconds since epoch), tuple[int, int] (HrTime), or datetime.
+            end_time: Optional explicit end time in the same formats as start_time.
         """
 
         super().__init__(
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py
index df08bf21..20456054 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py
@@ -62,8 +62,9 @@ def start(
             request: Optional request details for additional context
             caller_agent_details: Optional details of the caller agent
             caller_details: Optional details of the non-agentic caller
-            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
-            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
+            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
+                float (seconds since epoch), tuple[int, int] (HrTime), or datetime.
+            end_time: Optional explicit end time in the same formats as start_time.
 
         Returns:
             A new InvokeAgentScope instance
@@ -96,8 +97,9 @@ def __init__(
             request: Optional request details for additional context
             caller_agent_details: Optional details of the caller agent
             caller_details: Optional details of the non-agentic caller
-            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
-            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
+            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
+                float (seconds since epoch), tuple[int, int] (HrTime), or datetime.
+            end_time: Optional explicit end time in the same formats as start_time.
         """
         activity_name = INVOKE_AGENT_OPERATION_NAME
         if invoke_agent_details.details.agent_name:
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py
index 55066934..71dd6b50 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py
@@ -5,7 +5,6 @@
 
 import logging
 import os
-import time
 from datetime import datetime
 from threading import Lock
 from typing import TYPE_CHECKING, Any
@@ -111,7 +110,6 @@ def __init__(
                 instead of the current wall-clock time.
         """
         self._span: Span | None = None
-        self._wall_clock_start_ms = time.time() * 1000  # milliseconds
         self._custom_start_time: TimeInput = start_time
         self._custom_end_time: TimeInput = end_time
         self._has_ended = False

From 8354142efc03b46cbc765824b8bfec564bb73f83 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 24 Feb 2026 19:28:03 +0000
Subject: [PATCH 4/4] Simplify TimeInput type to just use datetime

Based on user feedback, simplify the start_time/end_time parameters to only accept
datetime objects instead of the complex TimeInput union type. This is more Pythonic
and consistent with existing code in the LangChain tracer.

Changes:
- Remove TimeInput type alias
- Change start_time/end_time parameters to datetime | None
- Add simple _datetime_to_ns() conversion method
- Remove unused _time_input_to_ns() and _time_input_to_ms() methods
- Update all scope subclasses to use datetime | None
- Simplify tests to only use datetime

Co-authored-by: nikhilNava <211831449+nikhilNava@users.noreply.github.com>
---
 .../observability/core/__init__.py            |   4 +-
 .../observability/core/execute_tool_scope.py  |  26 ++---
 .../observability/core/inference_scope.py     |  21 ++--
 .../observability/core/invoke_agent_scope.py  |  21 ++--
 .../observability/core/opentelemetry_scope.py |  97 +++++------------
 .../core/spans_scopes/output_scope.py         |  20 ++--
 .../core/test_custom_start_end_time.py        | 102 +++---------------
 7 files changed, 82 insertions(+), 209 deletions(-)

diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/__init__.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/__init__.py
index 47245187..e19cf8e9 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/__init__.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/__init__.py
@@ -24,7 +24,7 @@
 from .invoke_agent_details import InvokeAgentDetails
 from .invoke_agent_scope import InvokeAgentScope
 from .middleware.baggage_builder import BaggageBuilder
-from .opentelemetry_scope import OpenTelemetryScope, TimeInput
+from .opentelemetry_scope import OpenTelemetryScope
 from .request import Request
 from .source_metadata import SourceMetadata
 from .tenant_details import TenantDetails
@@ -47,8 +47,6 @@
     "SpanProcessor",
     # Base scope class
     "OpenTelemetryScope",
-    # Type aliases
-    "TimeInput",
     # Specific scope classes
     "ExecuteToolScope",
     "InvokeAgentScope",
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py
index 8b92e2b0..f22c02fe 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/execute_tool_scope.py
@@ -1,6 +1,8 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT License.
 
+from datetime import datetime
+
 from .agent_details import AgentDetails
 from .constants import (
     EXECUTE_TOOL_OPERATION_NAME,
@@ -15,7 +17,7 @@
     SERVER_ADDRESS_KEY,
     SERVER_PORT_KEY,
 )
-from .opentelemetry_scope import OpenTelemetryScope, TimeInput
+from .opentelemetry_scope import OpenTelemetryScope
 from .request import Request
 from .tenant_details import TenantDetails
 from .tool_call_details import ToolCallDetails
@@ -31,8 +33,8 @@ def start(
         tenant_details: TenantDetails,
         request: Request | None = None,
         parent_id: str | None = None,
-        start_time: TimeInput = None,
-        end_time: TimeInput = None,
+        start_time: datetime | None = None,
+        end_time: datetime | None = None,
     ) -> "ExecuteToolScope":
         """Creates and starts a new scope for tool execution tracing.
 
@@ -43,11 +45,10 @@ def start(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
-                float (seconds since epoch), tuple[int, int] (HrTime), or datetime. Useful when
+            start_time: Optional explicit start time as a datetime object. Useful when
                 recording a tool call after execution has already completed.
-            end_time: Optional explicit end time in the same formats as start_time. When
-                provided, the span will use this timestamp when disposed instead of the
+            end_time: Optional explicit end time as a datetime object. When provided,
+                the span will use this timestamp when disposed instead of the
                 current wall-clock time.
 
         Returns:
@@ -64,8 +65,8 @@ def __init__(
         tenant_details: TenantDetails,
         request: Request | None = None,
         parent_id: str | None = None,
-        start_time: TimeInput = None,
-        end_time: TimeInput = None,
+        start_time: datetime | None = None,
+        end_time: datetime | None = None,
     ):
         """Initialize the tool execution scope.
 
@@ -76,11 +77,10 @@ def __init__(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
-                float (seconds since epoch), tuple[int, int] (HrTime), or datetime. Useful when
+            start_time: Optional explicit start time as a datetime object. Useful when
                 recording a tool call after execution has already completed.
-            end_time: Optional explicit end time in the same formats as start_time. When
-                provided, the span will use this timestamp when disposed instead of the
+            end_time: Optional explicit end time as a datetime object. When provided,
+                the span will use this timestamp when disposed instead of the
                 current wall-clock time.
         """
         super().__init__(
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py
index e50863e7..a137ff14 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/inference_scope.py
@@ -1,6 +1,7 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT License.
 
+from datetime import datetime
 from typing import List
 
 from .agent_details import AgentDetails
@@ -19,7 +20,7 @@
     GEN_AI_USAGE_OUTPUT_TOKENS_KEY,
 )
 from .inference_call_details import InferenceCallDetails
-from .opentelemetry_scope import OpenTelemetryScope, TimeInput
+from .opentelemetry_scope import OpenTelemetryScope
 from .request import Request
 from .tenant_details import TenantDetails
 from .utils import safe_json_dumps
@@ -35,8 +36,8 @@ def start(
         tenant_details: TenantDetails,
         request: Request | None = None,
         parent_id: str | None = None,
-        start_time: TimeInput = None,
-        end_time: TimeInput = None,
+        start_time: datetime | None = None,
+        end_time: datetime | None = None,
     ) -> "InferenceScope":
         """Creates and starts a new scope for inference tracing.
 
@@ -47,9 +48,8 @@ def start(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
-                float (seconds since epoch), tuple[int, int] (HrTime), or datetime.
-            end_time: Optional explicit end time in the same formats as start_time.
+            start_time: Optional explicit start time as a datetime object.
+            end_time: Optional explicit end time as a datetime object.
 
         Returns:
             A new InferenceScope instance
@@ -65,8 +65,8 @@ def __init__(
         tenant_details: TenantDetails,
         request: Request | None = None,
         parent_id: str | None = None,
-        start_time: TimeInput = None,
-        end_time: TimeInput = None,
+        start_time: datetime | None = None,
+        end_time: datetime | None = None,
     ):
         """Initialize the inference scope.
 
@@ -77,9 +77,8 @@ def __init__(
             request: Optional request details for additional context
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
-                float (seconds since epoch), tuple[int, int] (HrTime), or datetime.
-            end_time: Optional explicit end time in the same formats as start_time.
+            start_time: Optional explicit start time as a datetime object.
+            end_time: Optional explicit end time as a datetime object.
         """
 
         super().__init__(
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py
index 20456054..fa8b8abe 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/invoke_agent_scope.py
@@ -4,6 +4,7 @@
 # Invoke agent scope for tracing agent invocation.
 
 import logging
+from datetime import datetime
 
 from .agent_details import AgentDetails
 from .constants import (
@@ -32,7 +33,7 @@
 )
 from .invoke_agent_details import InvokeAgentDetails
 from .models.caller_details import CallerDetails
-from .opentelemetry_scope import OpenTelemetryScope, TimeInput
+from .opentelemetry_scope import OpenTelemetryScope
 from .request import Request
 from .tenant_details import TenantDetails
 from .utils import safe_json_dumps, validate_and_normalize_ip
@@ -50,8 +51,8 @@ def start(
         request: Request | None = None,
         caller_agent_details: AgentDetails | None = None,
         caller_details: CallerDetails | None = None,
-        start_time: TimeInput = None,
-        end_time: TimeInput = None,
+        start_time: datetime | None = None,
+        end_time: datetime | None = None,
     ) -> "InvokeAgentScope":
         """Create and start a new scope for agent invocation tracing.
 
@@ -62,9 +63,8 @@ def start(
             request: Optional request details for additional context
             caller_agent_details: Optional details of the caller agent
             caller_details: Optional details of the non-agentic caller
-            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
-                float (seconds since epoch), tuple[int, int] (HrTime), or datetime.
-            end_time: Optional explicit end time in the same formats as start_time.
+            start_time: Optional explicit start time as a datetime object.
+            end_time: Optional explicit end time as a datetime object.
 
         Returns:
             A new InvokeAgentScope instance
@@ -86,8 +86,8 @@ def __init__(
         request: Request | None = None,
         caller_agent_details: AgentDetails | None = None,
         caller_details: CallerDetails | None = None,
-        start_time: TimeInput = None,
-        end_time: TimeInput = None,
+        start_time: datetime | None = None,
+        end_time: datetime | None = None,
     ):
         """Initialize the agent invocation scope.
 
@@ -97,9 +97,8 @@ def __init__(
             request: Optional request details for additional context
             caller_agent_details: Optional details of the caller agent
             caller_details: Optional details of the non-agentic caller
-            start_time: Optional explicit start time. Accepts int (nanoseconds since epoch),
-                float (seconds since epoch), tuple[int, int] (HrTime), or datetime.
-            end_time: Optional explicit end time in the same formats as start_time.
+            start_time: Optional explicit start time as a datetime object.
+            end_time: Optional explicit end time as a datetime object.
         """
         activity_name = INVOKE_AGENT_OPERATION_NAME
         if invoke_agent_details.details.agent_name:
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py
index 71dd6b50..e0365e9a 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/opentelemetry_scope.py
@@ -48,12 +48,6 @@
 # Create logger for this module - inherits from 'microsoft_agents_a365.observability.core'
 logger = logging.getLogger(__name__)
 
-# TimeInput is a type alias for types that can be used as span timestamps.
-# OpenTelemetry Python SDK accepts int (nanoseconds since epoch), float (seconds since epoch),
-# or a tuple of (seconds, nanoseconds) as HrTime.
-# We extend this to also accept datetime objects for convenience.
-TimeInput = int | float | tuple[int, int] | datetime | None
-
 
 class OpenTelemetryScope:
     """Base class for OpenTelemetry tracing scopes in the SDK."""
@@ -78,6 +72,20 @@ def _is_telemetry_enabled(cls) -> bool:
         enable_observability = os.getenv(ENABLE_A365_OBSERVABILITY, "").lower()
         return (env_value or enable_observability) in ("true", "1", "yes", "on")
 
+    @staticmethod
+    def _datetime_to_ns(dt: datetime | None) -> int | None:
+        """Convert a datetime to nanoseconds since epoch.
+
+        Args:
+            dt: Python datetime object, or None
+
+        Returns:
+            Nanoseconds since epoch, or None if input is None
+        """
+        if dt is None:
+            return None
+        return int(dt.timestamp() * 1_000_000_000)
+
     def __init__(
         self,
         kind: str,
@@ -86,8 +94,8 @@ def __init__(
         agent_details: "AgentDetails | None" = None,
         tenant_details: "TenantDetails | None" = None,
         parent_id: str | None = None,
-        start_time: TimeInput = None,
-        end_time: TimeInput = None,
+        start_time: datetime | None = None,
+        end_time: datetime | None = None,
     ):
         """Initialize the OpenTelemetry scope.
 
@@ -99,19 +107,15 @@ def __init__(
             tenant_details: Optional tenant details
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time. Can be:
-                - int: nanoseconds since epoch
-                - float: seconds since epoch
-                - tuple[int, int]: HrTime as (seconds, nanoseconds)
-                - datetime: Python datetime object
+            start_time: Optional explicit start time as a datetime object.
                 Useful when recording an operation after it has already completed.
-            end_time: Optional explicit end time in the same format as start_time.
+            end_time: Optional explicit end time as a datetime object.
                 When provided, the span will use this timestamp when disposed
                 instead of the current wall-clock time.
         """
         self._span: Span | None = None
-        self._custom_start_time: TimeInput = start_time
-        self._custom_end_time: TimeInput = end_time
+        self._custom_start_time: datetime | None = start_time
+        self._custom_end_time: datetime | None = end_time
         self._has_ended = False
         self._error_type: str | None = None
         self._exception: Exception | None = None
@@ -138,7 +142,7 @@ def __init__(
             span_context = parent_context if parent_context else context.get_current()
 
             # Convert custom start time to OTel-compatible format (nanoseconds since epoch)
-            otel_start_time = self._time_input_to_ns(start_time) if start_time else None
+            otel_start_time = self._datetime_to_ns(start_time)
 
             self._span = tracer.start_span(
                 activity_name,
@@ -256,59 +260,7 @@ def record_attributes(self, attributes: dict[str, Any] | list[tuple[str, Any]])
             if key and key.strip():
                 self._span.set_attribute(key, value)
 
-    @staticmethod
-    def _time_input_to_ns(t: TimeInput) -> int | None:
-        """Convert a TimeInput value to nanoseconds since epoch.
-
-        OpenTelemetry Python SDK accepts int (nanoseconds since epoch) for span
-        start_time and end_time parameters.
-
-        Args:
-            t: TimeInput value which can be:
-                - int: nanoseconds since epoch (returned as-is)
-                - float: seconds since epoch
-                - tuple[int, int]: HrTime as (seconds, nanoseconds)
-                - datetime: Python datetime object
-
-        Returns:
-            Nanoseconds since epoch, or None if input is None
-        """
-        if t is None:
-            return None
-        if isinstance(t, int):
-            # Assume nanoseconds if it's an integer
-            return t
-        if isinstance(t, float):
-            # Convert seconds to nanoseconds
-            return int(t * 1_000_000_000)
-        if isinstance(t, tuple) and len(t) == 2:
-            # HrTime: (seconds, nanoseconds)
-            seconds, nanos = t
-            return seconds * 1_000_000_000 + nanos
-        if isinstance(t, datetime):
-            return int(t.timestamp() * 1_000_000_000)
-        logger.warning(
-            f"_time_input_to_ns received unexpected TimeInput "
-            f"(type={type(t).__name__}); returning None"
-        )
-        return None
-
-    @staticmethod
-    def _time_input_to_ms(t: TimeInput) -> float | None:
-        """Convert a TimeInput value to milliseconds since epoch.
-
-        Used for duration calculations.
-
-        Args:
-            t: TimeInput value (see _time_input_to_ns for accepted types)
-
-        Returns:
-            Milliseconds since epoch, or None if input is None
-        """
-        ns = OpenTelemetryScope._time_input_to_ns(t)
-        return ns / 1_000_000 if ns is not None else None
-
-    def set_end_time(self, end_time: TimeInput) -> None:
+    def set_end_time(self, end_time: datetime) -> None:
         """Set a custom end time for the scope.
 
         When set, dispose() will pass this value to span.end() instead of using
@@ -316,8 +268,7 @@ def set_end_time(self, end_time: TimeInput) -> None:
         the operation is known before the scope is disposed.
 
         Args:
-            end_time: The end time as nanoseconds since epoch, seconds since epoch,
-                     HrTime tuple (seconds, nanoseconds), or datetime object.
+            end_time: The end time as a datetime object.
         """
         self._custom_end_time = end_time
 
@@ -329,7 +280,7 @@ def _end(self) -> None:
             logger.info(f"Span ended: '{self._span.name}' ({span_id})")
 
             # Convert custom end time to OTel-compatible format (nanoseconds since epoch)
-            otel_end_time = self._time_input_to_ns(self._custom_end_time)
+            otel_end_time = self._datetime_to_ns(self._custom_end_time)
             if otel_end_time is not None:
                 self._span.end(end_time=otel_end_time)
             else:
diff --git a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/spans_scopes/output_scope.py b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/spans_scopes/output_scope.py
index 4f526058..873a9dc9 100644
--- a/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/spans_scopes/output_scope.py
+++ b/libraries/microsoft-agents-a365-observability-core/microsoft_agents_a365/observability/core/spans_scopes/output_scope.py
@@ -1,10 +1,12 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT License.
 
+from datetime import datetime
+
 from ..agent_details import AgentDetails
 from ..constants import GEN_AI_OUTPUT_MESSAGES_KEY
 from ..models.response import Response
-from ..opentelemetry_scope import OpenTelemetryScope, TimeInput
+from ..opentelemetry_scope import OpenTelemetryScope
 from ..tenant_details import TenantDetails
 from ..utils import safe_json_dumps
 
@@ -20,8 +22,8 @@ def start(
         tenant_details: TenantDetails,
         response: Response,
         parent_id: str | None = None,
-        start_time: TimeInput = None,
-        end_time: TimeInput = None,
+        start_time: datetime | None = None,
+        end_time: datetime | None = None,
     ) -> "OutputScope":
         """Creates and starts a new scope for output tracing.
 
@@ -31,8 +33,8 @@ def start(
             response: The response details from the agent
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
-            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
+            start_time: Optional explicit start time as a datetime object.
+            end_time: Optional explicit end time as a datetime object.
 
         Returns:
             A new OutputScope instance
@@ -45,8 +47,8 @@ def __init__(
         tenant_details: TenantDetails,
         response: Response,
         parent_id: str | None = None,
-        start_time: TimeInput = None,
-        end_time: TimeInput = None,
+        start_time: datetime | None = None,
+        end_time: datetime | None = None,
     ):
         """Initialize the output scope.
 
@@ -56,8 +58,8 @@ def __init__(
             response: The response details from the agent
             parent_id: Optional parent Activity ID used to link this span to an upstream
                 operation
-            start_time: Optional explicit start time (ms epoch, Date, or HrTime)
-            end_time: Optional explicit end time (ms epoch, Date, or HrTime)
+            start_time: Optional explicit start time as a datetime object.
+            end_time: Optional explicit end time as a datetime object.
         """
         super().__init__(
             kind="Client",
diff --git a/tests/observability/core/test_custom_start_end_time.py b/tests/observability/core/test_custom_start_end_time.py
index cb824c02..080e4caf 100644
--- a/tests/observability/core/test_custom_start_end_time.py
+++ b/tests/observability/core/test_custom_start_end_time.py
@@ -5,6 +5,7 @@
 
 import os
 import sys
+import time
 import unittest
 from datetime import UTC, datetime
 from pathlib import Path
@@ -78,31 +79,6 @@ def _get_finished_span(self):
         self.assertTrue(finished_spans, "Expected at least one span to be created")
         return finished_spans[-1]
 
-    def test_custom_start_and_end_time_with_nanoseconds(self):
-        """Test that constructor-provided start and end times are recorded on the span."""
-        # Use nanoseconds since epoch
-        custom_start_ns = 1700000000000000000  # 2023-11-14T22:13:20Z
-        custom_end_ns = 1700000005000000000  # 5 seconds later
-
-        scope = ExecuteToolScope.start(
-            self.tool_details,
-            self.agent_details,
-            self.tenant_details,
-            start_time=custom_start_ns,
-            end_time=custom_end_ns,
-        )
-        scope.dispose()
-
-        span = self._get_finished_span()
-
-        # OTel Python SDK stores times as nanoseconds (int)
-        span_start_ns = span.start_time
-        span_end_ns = span.end_time
-
-        # Verify start and end times are close to what we provided
-        self.assertAlmostEqual(span_start_ns, custom_start_ns, delta=1000)  # 1μs tolerance
-        self.assertAlmostEqual(span_end_ns, custom_end_ns, delta=1000)
-
     def test_custom_start_and_end_time_with_datetime(self):
         """Test that datetime objects are correctly converted to span timestamps."""
         custom_start = datetime(2023, 11, 14, 22, 13, 20, tzinfo=UTC)
@@ -128,84 +104,31 @@ def test_custom_start_and_end_time_with_datetime(self):
         self.assertAlmostEqual(span_start_ns, expected_start_ns, delta=1000)
         self.assertAlmostEqual(span_end_ns, expected_end_ns, delta=1000)
 
-    def test_custom_start_and_end_time_with_float_seconds(self):
-        """Test that float seconds are correctly converted to span timestamps."""
-        # Float seconds since epoch
-        custom_start_sec = 1700000000.0  # 2023-11-14T22:13:20Z
-        custom_end_sec = 1700000005.5  # 5.5 seconds later
-
-        scope = ExecuteToolScope.start(
-            self.tool_details,
-            self.agent_details,
-            self.tenant_details,
-            start_time=custom_start_sec,
-            end_time=custom_end_sec,
-        )
-        scope.dispose()
-
-        span = self._get_finished_span()
-
-        expected_start_ns = int(custom_start_sec * 1_000_000_000)
-        expected_end_ns = int(custom_end_sec * 1_000_000_000)
-
-        span_start_ns = span.start_time
-        span_end_ns = span.end_time
-
-        self.assertAlmostEqual(span_start_ns, expected_start_ns, delta=1000)
-        self.assertAlmostEqual(span_end_ns, expected_end_ns, delta=1000)
-
-    def test_custom_start_and_end_time_with_hrtime_tuple(self):
-        """Test that HrTime tuples (seconds, nanoseconds) are correctly handled."""
-        # HrTime: (seconds, nanoseconds)
-        custom_start: tuple[int, int] = (1700000000, 0)  # 2023-11-14T22:13:20Z
-        custom_end: tuple[int, int] = (1700000005, 500000000)  # 5.5 seconds later
-
-        scope = ExecuteToolScope.start(
-            self.tool_details,
-            self.agent_details,
-            self.tenant_details,
-            start_time=custom_start,
-            end_time=custom_end,
-        )
-        scope.dispose()
-
-        span = self._get_finished_span()
-
-        expected_start_ns = custom_start[0] * 1_000_000_000 + custom_start[1]
-        expected_end_ns = custom_end[0] * 1_000_000_000 + custom_end[1]
-
-        span_start_ns = span.start_time
-        span_end_ns = span.end_time
-
-        self.assertAlmostEqual(span_start_ns, expected_start_ns, delta=1000)
-        self.assertAlmostEqual(span_end_ns, expected_end_ns, delta=1000)
-
     def test_set_end_time_overrides_end_time(self):
         """Test that set_end_time overrides the end time when called before dispose."""
-        custom_start_ns = 1700000040000000000
-        initial_end_ns = 1700000045000000000  # 5 seconds after start
-        later_end_ns = 1700000048000000000  # 8 seconds after start
+        custom_start = datetime(2023, 11, 14, 22, 13, 40, tzinfo=UTC)
+        initial_end = datetime(2023, 11, 14, 22, 13, 45, tzinfo=UTC)  # 5 seconds after start
+        later_end = datetime(2023, 11, 14, 22, 13, 48, tzinfo=UTC)  # 8 seconds after start
 
         scope = ExecuteToolScope.start(
             self.tool_details,
             self.agent_details,
             self.tenant_details,
-            start_time=custom_start_ns,
-            end_time=initial_end_ns,
+            start_time=custom_start,
+            end_time=initial_end,
         )
         # Override the end time
-        scope.set_end_time(later_end_ns)
+        scope.set_end_time(later_end)
         scope.dispose()
 
         span = self._get_finished_span()
 
+        expected_end_ns = int(later_end.timestamp() * 1_000_000_000)
         span_end_ns = span.end_time
-        self.assertAlmostEqual(span_end_ns, later_end_ns, delta=1000)
+        self.assertAlmostEqual(span_end_ns, expected_end_ns, delta=1000)
 
     def test_wall_clock_time_used_when_no_custom_times(self):
         """Test that wall-clock time is used when no custom times are provided."""
-        import time
-
         before = time.time_ns()
         scope = ExecuteToolScope.start(
             self.tool_details,
@@ -227,22 +150,23 @@ def test_wall_clock_time_used_when_no_custom_times(self):
 
     def test_only_start_time_provided(self):
         """Test that only custom start time can be provided without end time."""
-        custom_start_ns = 1700000000000000000
+        custom_start = datetime(2023, 11, 14, 22, 13, 20, tzinfo=UTC)
 
         scope = ExecuteToolScope.start(
             self.tool_details,
             self.agent_details,
             self.tenant_details,
-            start_time=custom_start_ns,
+            start_time=custom_start,
         )
         scope.dispose()
 
         span = self._get_finished_span()
 
+        expected_start_ns = int(custom_start.timestamp() * 1_000_000_000)
         span_start_ns = span.start_time
 
         # Start time should match what we provided
-        self.assertAlmostEqual(span_start_ns, custom_start_ns, delta=1000)
+        self.assertAlmostEqual(span_start_ns, expected_start_ns, delta=1000)
 
         # End time should be close to current time (not custom)
         span_end_ns = span.end_time