diff --git a/solstone/apps/entities/routes.py b/solstone/apps/entities/routes.py
index 37f579b87..a55b966e9 100644
--- a/solstone/apps/entities/routes.py
+++ b/solstone/apps/entities/routes.py
@@ -63,10 +63,12 @@ from solstone.think.entities import (
     count_observations,
     delete_detected_entity,
     detach_facet_entity,
+    entity_last_active_day,
     entity_last_active_ts,
     entity_memory_path,
     entity_slug,
     is_valid_entity_type,
+    last_active_day_for_ts,
     load_all_facet_relationships,
     load_all_journal_entities,
     load_detected_entities_recent,
@@ -144,6 +146,7 @@ def get_facet_entities_data(facet_name: str) -> dict:
             entity["has_voiceprint"] = metadata["has_voiceprint"]
         # Add computed activity timestamp for frontend sorting/display
         entity["last_active_ts"] = entity_last_active_ts(entity)
+        entity["last_active_day"] = entity_last_active_day(entity)
 
     # Load detected entities directly from files (excludes attached names/akas)
     detected = load_detected_entities_recent(facet_name)
@@ -805,6 +808,7 @@ def get_entity(facet_name: str, entity_id: str) -> Any:
         entity["has_voiceprint"] = metadata["has_voiceprint"]
         # Add computed activity timestamp for frontend display
         entity["last_active_ts"] = entity_last_active_ts(entity)
+        entity["last_active_day"] = entity_last_active_day(entity)
 
         # Ensure id is set
         if "id" not in entity:
@@ -1294,6 +1298,7 @@ def _build_facet_relationships(
         # Compute last_active_ts for this relationship
         rel_active_ts = entity_last_active_ts(relationship)
         facet_rel["last_active_ts"] = rel_active_ts
+        facet_rel["last_active_day"] = entity_last_active_day(relationship)
 
         # Only count observations and activity from non-detached relationships
         if not is_detached:
@@ -1348,6 +1353,9 @@ def get_journal_entities_data() -> dict:
             "facets": facet_relationships,
             "total_observation_count": total_observation_count,
             "last_active_ts": latest_active_ts,
+            "last_active_day": (
+                last_active_day_for_ts(latest_active_ts) if latest_active_ts else None
+            ),
         }
 
         entities.append(enriched)
@@ -1407,6 +1415,9 @@ def get_journal_entity(entity_id: str) -> Any:
             "facets": facet_relationships,
             "total_observation_count": total_observation_count,
             "last_active_ts": latest_active_ts,
+            "last_active_day": (
+                last_active_day_for_ts(latest_active_ts) if latest_active_ts else None
+            ),
         }
 
         return jsonify({"entity": enriched})
diff --git a/solstone/apps/entities/workspace.html b/solstone/apps/entities/workspace.html
index 934b6f88b..61c3c5a36 100644
--- a/solstone/apps/entities/workspace.html
+++ b/solstone/apps/entities/workspace.html
@@ -1716,18 +1716,10 @@ function formatDateShort(dateStr) {
   return short;
 }
 
-// Format timestamp (epoch ms) to relative date
-function formatTimestamp(epochMs) {
-  if (!epochMs) return null;
-  const date = new Date(epochMs);
-  const dateStr = date.toISOString().slice(0, 10).replace(/-/g, '');
-  return formatDateShort(dateStr);
-}
-
-// Get display date for entity using pre-computed last_active_ts from server
+// Get display date for entity using server-derived journal-local day (YYYYMMDD)
 function getEntityDisplayDate(entity) {
   if (entity.last_active_ts) {
-    return formatTimestamp(entity.last_active_ts);
+    return formatDateShort(entity.last_active_day);
   }
   return null;
 }
@@ -2077,7 +2069,7 @@ function renderJournalDetailView(entity) {
 
       if (facet.last_active_ts) {
         const date = document.createElement('span');
-        date.textContent = formatTimestamp(facet.last_active_ts);
+        date.textContent = formatDateShort(facet.last_active_day);
         meta.appendChild(date);
       }
 
diff --git a/solstone/think/entities/__init__.py b/solstone/think/entities/__init__.py
index e59ca0287..05b97b3e0 100644
--- a/solstone/think/entities/__init__.py
+++ b/solstone/think/entities/__init__.py
@@ -37,10 +37,12 @@ from solstone.think.entities.core import (
     ENTITY_TYPES,
     MAX_ENTITY_SLUG_LENGTH,
     EntityDict,
+    entity_last_active_day,
     entity_last_active_ts,
     entity_slug,
     get_identity_names,
     is_valid_entity_type,
+    last_active_day_for_ts,
 )
 
 # Errors
@@ -143,7 +145,9 @@ __all__ = [
     "ENTITY_TYPES",
     "MAX_ENTITY_SLUG_LENGTH",
     "EntityDict",
+    "entity_last_active_day",
     "entity_last_active_ts",
+    "last_active_day_for_ts",
     "entity_slug",
     "get_identity_names",
     "is_valid_entity_type",
diff --git a/solstone/think/entities/core.py b/solstone/think/entities/core.py
index a3ab28dc4..cb3cc4b4b 100644
--- a/solstone/think/entities/core.py
+++ b/solstone/think/entities/core.py
@@ -135,6 +135,34 @@ def entity_last_active_ts(entity: EntityDict) -> int:
     return DEFAULT_ACTIVITY_TS
 
 
+def last_active_day_for_ts(ts_ms: int) -> str:
+    """Convert a last-active epoch (ms) to a journal-local day string (YYYYMMDD).
+
+    Journal days bucket on local time (datetime.now()-based, e.g.
+    solstone.think.utils.day_path), so an instant is derived in local time here
+    too. This keeps a "now" timestamp on today's journal day instead of slipping
+    to the next UTC day for evening-Americas edits.
+    """
+    return datetime.fromtimestamp(ts_ms / 1000).strftime("%Y%m%d")
+
+
+def entity_last_active_day(entity: EntityDict) -> str:
+    """Get the entity's last-active day as a journal-local YYYYMMDD string.
+
+    Day-basis sibling of entity_last_active_ts(). Returns last_seen verbatim when
+    it is already a valid journal-day string (avoids a lossy epoch round-trip);
+    otherwise derives the day from entity_last_active_ts() on the local basis.
+    """
+    last_seen = entity.get("last_seen")
+    if last_seen and isinstance(last_seen, str) and len(last_seen) == 8:
+        try:
+            datetime.strptime(last_seen, "%Y%m%d")
+            return last_seen
+        except ValueError:
+            pass  # Malformed, fall through to epoch derivation
+    return last_active_day_for_ts(entity_last_active_ts(entity))
+
+
 def is_valid_entity_type(etype: str) -> bool:
     """Validate entity type: alphanumeric and spaces only, at least 3 characters."""
     if not etype or len(etype.strip()) < 3:
diff --git a/tests/baselines/api/entities/journal-entities.json b/tests/baselines/api/entities/journal-entities.json
index ad9e328b2..943f46d70 100644
--- a/tests/baselines/api/entities/journal-entities.json
+++ b/tests/baselines/api/entities/journal-entities.json
@@ -6,6 +6,7 @@
       "facets": [],
       "id": "alice_johnson",
       "is_principal": false,
+      "last_active_day": null,
       "last_active_ts": 0,
       "name": "Alice Johnson",
       "total_observation_count": 0,
@@ -17,6 +18,7 @@
       "facets": [],
       "id": "bob_smith",
       "is_principal": false,
+      "last_active_day": null,
       "last_active_ts": 0,
       "name": "Bob Smith",
       "total_observation_count": 0,
@@ -32,6 +34,7 @@
           "description": "Container platform",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -42,6 +45,7 @@
       ],
       "id": "docker",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Docker",
       "total_observation_count": 0,
@@ -57,6 +61,7 @@
           "description": "Database system",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -67,6 +72,7 @@
       ],
       "id": "postgresql",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "PostgreSQL",
       "total_observation_count": 0,
@@ -82,6 +88,7 @@
           "description": "Lead developer on the project",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -92,6 +99,7 @@
       ],
       "id": "john_smith",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "John Smith",
       "total_observation_count": 2,
@@ -107,6 +115,7 @@
           "description": "Main client",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -117,6 +126,7 @@
       ],
       "id": "acme_corp",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Acme Corp",
       "total_observation_count": 0,
@@ -132,6 +142,7 @@
           "description": "Partner company",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -142,6 +153,7 @@
       ],
       "id": "tech_solutions_inc",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Tech Solutions Inc",
       "total_observation_count": 0,
@@ -157,6 +169,7 @@
           "description": "Performance improvement initiative",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -167,6 +180,7 @@
       ],
       "id": "api_optimization",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "API Optimization",
       "total_observation_count": 0,
@@ -182,6 +196,7 @@
           "description": "Primary IDE",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -192,6 +207,7 @@
       ],
       "id": "visual_studio_code",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Visual Studio Code",
       "total_observation_count": 0,
@@ -207,6 +223,7 @@
           "description": "Project manager",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -217,6 +234,7 @@
       ],
       "id": "jane_doe",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Jane Doe",
       "total_observation_count": 0,
@@ -232,6 +250,7 @@
           "description": "QA engineer",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -242,6 +261,7 @@
       ],
       "id": "bob_wilson",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Bob Wilson",
       "total_observation_count": 0,
@@ -257,6 +277,7 @@
           "description": "UI/UX overhaul project",
           "emoji": "🧪",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "test-facet",
@@ -267,6 +288,7 @@
       ],
       "id": "dashboard_redesign",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Dashboard Redesign",
       "total_observation_count": 0,
@@ -282,6 +304,7 @@
           "description": "CTO and co-founder of Montague Tech. Visionary full-stack engineer.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -295,6 +318,7 @@
           "description": "Co-lead of the Verona Platform joint venture from Montague Tech.",
           "emoji": "🌹",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "verona",
@@ -305,6 +329,7 @@
       ],
       "id": "romeo_montague",
       "is_principal": true,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Romeo Montague",
       "total_observation_count": 6,
@@ -320,6 +345,7 @@
           "description": "CTO of Capulet Industries. Secret collaborator on the Verona Platform.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -333,6 +359,7 @@
           "description": "Co-lead of the Verona Platform joint venture from Capulet Industries.",
           "emoji": "🌹",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "verona",
@@ -346,6 +373,7 @@
           "description": "Lead software architect at Capulet Industries.",
           "emoji": "🏰",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "capulet",
@@ -356,6 +384,7 @@
       ],
       "id": "juliet_capulet",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Juliet Capulet",
       "total_observation_count": 9,
@@ -371,6 +400,7 @@
           "description": "Core distributed mesh routing technology powering Montague Tech's API platform.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -381,6 +411,7 @@
       ],
       "id": "mesh_routing",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Mesh Routing",
       "total_observation_count": 3,
@@ -396,6 +427,7 @@
           "description": "Encrypted messaging app — the original collaboration project between Romeo and Juliet.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -409,6 +441,7 @@
           "description": "Encrypted messaging app built by Romeo and Juliet for secure collaboration.",
           "emoji": "🌹",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "verona",
@@ -419,6 +452,7 @@
       ],
       "id": "balcony_app",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Balcony App",
       "total_observation_count": 2,
@@ -434,6 +468,7 @@
           "description": "Family tech startup specializing in API development.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -444,6 +479,7 @@
       ],
       "id": "montague_tech",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Montague Tech",
       "total_observation_count": 3,
@@ -459,6 +495,7 @@
           "description": "Former colleague who left for Verona Ventures. Maintains industry contacts.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -469,6 +506,7 @@
       ],
       "id": "rosaline_prince",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Rosaline Prince",
       "total_observation_count": 2,
@@ -484,6 +522,7 @@
           "description": "Junior developer on the mesh routing team. Romeo's mentee.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -494,6 +533,7 @@
       ],
       "id": "balthasar_davi",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Balthasar Davi",
       "total_observation_count": 2,
@@ -509,6 +549,7 @@
           "description": "Romeo's best friend. Freelance security consultant.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -519,6 +560,7 @@
       ],
       "id": "mercutio_escalus",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Mercutio Escalus",
       "total_observation_count": 3,
@@ -534,6 +576,7 @@
           "description": "Romeo's cousin. DevOps lead at Montague Tech.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -544,6 +587,7 @@
       ],
       "id": "benvolio_montague",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Benvolio Montague",
       "total_observation_count": 3,
@@ -559,6 +603,7 @@
           "description": "Senior architect and trusted advisor. Mediating the Montague-Capulet technical partnership.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -572,6 +617,7 @@
           "description": "Professor at Verona Tech University. Mentor and advisor to both Romeo and Juliet.",
           "emoji": "🌹",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "verona",
@@ -582,6 +628,7 @@
       ],
       "id": "friar_lawrence",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Friar Lawrence",
       "total_observation_count": 4,
@@ -597,6 +644,7 @@
           "description": "The unified cross-company API gateway combining Montague routing with Capulet schema translation.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -610,6 +658,7 @@
           "description": "Secret cross-company unified API gateway project.",
           "emoji": "🌹",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "verona",
@@ -620,6 +669,7 @@
       ],
       "id": "verona_platform",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Verona Platform",
       "total_observation_count": 3,
@@ -635,6 +685,7 @@
           "description": "Translation layer enabling Capulet's enterprise schemas to work with Montague's mesh routing.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -645,6 +696,7 @@
       ],
       "id": "schema_bridge",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Schema Bridge",
       "total_observation_count": 2,
@@ -660,6 +712,7 @@
           "description": "VC partner observing Montague Tech board. Interested in the Verona Platform potential.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -670,6 +723,7 @@
       ],
       "id": "prince_escalus",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Prince Escalus",
       "total_observation_count": 2,
@@ -685,6 +739,7 @@
           "description": "Venture capital firm backing both Montague Tech and Capulet Industries.",
           "emoji": "⚔️",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "montague",
@@ -695,6 +750,7 @@
       ],
       "id": "verona_ventures",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Verona Ventures",
       "total_observation_count": 2,
@@ -710,6 +766,7 @@
           "description": "",
           "emoji": "🚀",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "full-featured",
@@ -720,6 +777,7 @@
       ],
       "id": "first_test_entity",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "First test entity",
       "total_observation_count": 0,
@@ -735,6 +793,7 @@
           "description": "",
           "emoji": "🚀",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "full-featured",
@@ -745,6 +804,7 @@
       ],
       "id": "second_test_entity",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Second test entity",
       "total_observation_count": 0,
@@ -760,6 +820,7 @@
           "description": "",
           "emoji": "🚀",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "full-featured",
@@ -770,6 +831,7 @@
       ],
       "id": "third_test_entity_with_description",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Third test entity with description",
       "total_observation_count": 0,
@@ -785,6 +847,7 @@
           "description": "Family enterprise software company. Enterprise API solutions.",
           "emoji": "🏰",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "capulet",
@@ -795,6 +858,7 @@
       ],
       "id": "capulet_industries",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Capulet Industries",
       "total_observation_count": 0,
@@ -810,6 +874,7 @@
           "description": "Juliet's cousin. VP of Engineering at Capulet Industries.",
           "emoji": "🏰",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "capulet",
@@ -820,6 +885,7 @@
       ],
       "id": "tybalt_capulet",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Tybalt Capulet",
       "total_observation_count": 4,
@@ -835,6 +901,7 @@
           "description": "Juliet's trusted executive assistant and office manager.",
           "emoji": "🏰",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "capulet",
@@ -845,6 +912,7 @@
       ],
       "id": "nurse_angela",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Nurse Angela",
       "total_observation_count": 2,
@@ -860,6 +928,7 @@
           "description": "VC investor courting Capulet Industries for a strategic partnership.",
           "emoji": "🏰",
           "has_voiceprint": false,
+          "last_active_day": "20251231",
           "last_active_ts": 1767225600000,
           "last_seen": null,
           "name": "capulet",
@@ -870,6 +939,7 @@
       ],
       "id": "paris_duke",
       "is_principal": false,
+      "last_active_day": "20251231",
       "last_active_ts": 1767225600000,
       "name": "Paris Duke",
       "total_observation_count": 2,
diff --git a/tests/baselines/api/entities/journal-entity-detail.json b/tests/baselines/api/entities/journal-entity-detail.json
index 215c8a0ea..d8f5ae9c8 100644
--- a/tests/baselines/api/entities/journal-entity-detail.json
+++ b/tests/baselines/api/entities/journal-entity-detail.json
@@ -9,6 +9,7 @@
         "description": "",
         "emoji": "🚀",
         "has_voiceprint": false,
+        "last_active_day": "20251231",
         "last_active_ts": 1767225600000,
         "last_seen": null,
         "name": "full-featured",
@@ -19,6 +20,7 @@
     ],
     "id": "first_test_entity",
     "is_principal": false,
+    "last_active_day": "20251231",
     "last_active_ts": 1767225600000,
     "name": "First test entity",
     "total_observation_count": 0,
diff --git a/tests/test_entities.py b/tests/test_entities.py
index 9a994bda2..fb64acd98 100644
--- a/tests/test_entities.py
+++ b/tests/test_entities.py
@@ -20,12 +20,14 @@ from solstone.think.entities import (
     detach_facet_entity,
     detected_entities_path,
     ensure_entity_memory,
+    entity_last_active_day,
     entity_last_active_ts,
     entity_memory_path,
     entity_slug,
     find_matching_entity,
     get_identity_names,
     iter_detected_entity_names_since,
+    last_active_day_for_ts,
     load_all_attached_entities,
     load_all_facet_relationships,
     load_all_journal_entities,
@@ -144,6 +146,67 @@ def test_entity_last_active_ts_zero_timestamps():
     assert ts == DEFAULT_ACTIVITY_TS
 
 
+@pytest.fixture
+def tz_americas_evening(monkeypatch):
+    """Pin process tz to US Eastern so a UTC-next-day instant is the same local day.
+
+    Journal days bucket on local time, so the derived last-active day must follow
+    local time — this is the evening-Americas case that produced "Tomorrow".
+    """
+    import os
+    import time
+
+    original_tz = os.environ.get("TZ")
+    monkeypatch.setenv("TZ", "America/New_York")
+    time.tzset()
+    yield
+    if original_tz is None:
+        os.environ.pop("TZ", None)
+    else:
+        os.environ["TZ"] = original_tz
+    time.tzset()
+
+
+def test_last_active_day_for_ts_uses_local_journal_day(tz_americas_evening):
+    """Evening-Americas instant renders the local journal day, not the next UTC day."""
+    from datetime import datetime, timezone
+
+    # 2026-01-15 23:30 America/New_York == 2026-01-16 04:30 UTC.
+    instant = datetime(2026, 1, 16, 4, 30, tzinfo=timezone.utc)
+    ts_ms = int(instant.timestamp() * 1000)
+
+    assert last_active_day_for_ts(ts_ms) == "20260115"  # local journal day (the fix)
+    assert last_active_day_for_ts(ts_ms) != "20260116"  # NOT the next UTC day (the bug)
+
+
+def test_entity_last_active_day_from_updated_at_local_basis(tz_americas_evening):
+    """entity_last_active_day derives the local journal day from the updated_at epoch."""
+    from datetime import datetime, timezone
+
+    instant = datetime(2026, 1, 16, 4, 30, tzinfo=timezone.utc)
+    ts_ms = int(instant.timestamp() * 1000)
+
+    assert entity_last_active_day({"updated_at": ts_ms}) == "20260115"
+
+
+def test_entity_last_active_day_returns_last_seen_verbatim():
+    """A valid last_seen journal-day string is returned without an epoch round-trip."""
+    entity = {"last_seen": "20260115", "updated_at": 1700000000000}
+    assert entity_last_active_day(entity) == "20260115"
+
+
+def test_entity_last_active_day_malformed_last_seen_falls_through(
+    tz_americas_evening,
+):
+    """Malformed last_seen falls through to the epoch-derived local day."""
+    from datetime import datetime, timezone
+
+    instant = datetime(2026, 1, 16, 4, 30, tzinfo=timezone.utc)
+    ts_ms = int(instant.timestamp() * 1000)
+    entity = {"last_seen": "invalid", "updated_at": ts_ms}
+    assert entity_last_active_day(entity) == "20260115"
+
+
 def test_entity_last_active_ts_negative_timestamps():
     """Test that negative timestamps are treated as missing."""
     entity = {