diff --git a/headroom/proxy/outcome.py b/headroom/proxy/outcome.py
index e0b304d4c..5a23acc04 100644
--- a/headroom/proxy/outcome.py
+++ b/headroom/proxy/outcome.py
@@ -27,7 +27,7 @@ from __future__ import annotations
 
 import logging
 from dataclasses import dataclass, field
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Any
 
 from headroom.proxy.tool_schema_savings_policy import (
@@ -526,7 +526,10 @@ async def emit_request_outcome(handler: Any, outcome: RequestOutcome) -> None:
         request_logger.log(
             RequestLog(
                 request_id=outcome.request_id,
-                timestamp=datetime.now().isoformat(),
+                # Request logs are consumed by browsers in arbitrary time zones.
+                # Include the UTC offset so relative-age calculations represent
+                # the same instant regardless of where the proxy runs.
+                timestamp=datetime.now(timezone.utc).isoformat(),
                 provider=outcome.provider,
                 model=outcome.model,
                 input_tokens_original=outcome.original_tokens,
diff --git a/tests/test_request_outcome.py b/tests/test_request_outcome.py
index 09936a094..d2295a5ea 100644
--- a/tests/test_request_outcome.py
+++ b/tests/test_request_outcome.py
@@ -15,6 +15,7 @@ import asyncio
 import contextlib
 import logging
 from dataclasses import FrozenInstanceError
+from datetime import datetime, timezone
 from typing import Any
 from unittest.mock import AsyncMock, MagicMock
 
@@ -325,6 +326,22 @@ async def test_funnel_logs_request_with_derived_cache_hit() -> None:
     assert log_entry.cache_hit is True
 
 
+@pytest.mark.asyncio
+async def test_funnel_logs_request_timestamp_with_utc_offset() -> None:
+    """Recent-request timestamps must identify an absolute instant.
+
+    A naive ISO timestamp is interpreted in the browser's local timezone,
+    which makes the dashboard show negative ages when the proxy and browser
+    use different timezone settings.
+    """
+    h = _FunnelHarness()
+    await h._record_request_outcome(_outcome())
+
+    timestamp = datetime.fromisoformat(h.logger.logs[0].timestamp)
+    assert timestamp.tzinfo is not None
+    assert timestamp.utcoffset() == timezone.utc.utcoffset(timestamp)
+
+
 @pytest.mark.asyncio
 async def test_funnel_skips_request_log_when_logger_absent() -> None:
     """Same pattern as cost_tracker — optional surface."""