Compare cited evidence times chronologically across time zones

docs/design/management-operation-boundaries.md

@@ -42,3 +42,5 @@ preserves Unicode, case, order, repetition, punctuation and internal whitespace.
 paths, weights and bookkeeping timestamps do not establish semantic identity. The oldest
 duplicate remains active, with name breaking creation-time ties; other copies retain their
 files and point to it. Similarity alone belongs to the reviewed proposal path.
+
+The implicit fact date selects the latest cited instant by parsed timestamp rather than string order. Evidence using different UTC offsets retains its actual chronological meaning.

packages/core/src/agent_memory/core/reconcile.py

@@ -11,6 +11,7 @@
 import json
 import re
 
+from . import timestamp
 from .config import Config
 from .errors import FieldError
 from .paths import StoreLayout
@@ -228,7 +229,7 @@ def _latest_cited_time(pointers: list[Pointer], sheet: Sheet) -> str:
             for pointer in pointers
         )
     ]
-    return max(stamps) if stamps else ""
+    return max(stamps, key=timestamp.parse) if stamps else ""
 
 
 def _provenance(raw: object, sheet: Sheet) -> list[Pointer]:

tests/unit/test_regression_evidence_time_order.py

@@ -0,0 +1,18 @@
+from agent_memory.core import reconcile, sessions
+
+
+def test_default_fact_date_uses_latest_instant_not_lexical_zone_order(store):
+    pointer = store.archive.append_session(
+        "zoned",
+        [
+            {"text": "Earlier evidence", "at": "2026-01-05T10:00:00+02:00"},
+            {"text": "Later evidence", "at": "2026-01-05T09:00:00Z"},
+        ],
+    )
+    messages = sessions.resolve(store.layout, pointer)
+    sheet = reconcile.build(store, "zoned", messages)
+    spec = reconcile.to_record_spec(
+        {"op": "new", "type": "fact", "fields": {"subject": "zone"}, "abstract": "Time fixture"},
+        sheet,
+    )
+    assert spec["valid_from"] == "2026-01-05T09:00:00Z"