diff --git a/src/basic_memory/api/routers/resource_router.py b/src/basic_memory/api/routers/resource_router.py
index 59cc9273..1b64c0c3 100644
--- a/src/basic_memory/api/routers/resource_router.py
+++ b/src/basic_memory/api/routers/resource_router.py
@@ -25,6 +25,17 @@ from datetime import datetime
 router = APIRouter(prefix="/resource", tags=["resources"])
 
 
+def _mtime_to_datetime(entity: EntityModel) -> datetime:
+    """Convert entity mtime (file modification time) to datetime.
+
+    Returns the file's actual modification time, falling back to updated_at
+    if mtime is not available.
+    """
+    if entity.mtime:
+        return datetime.fromtimestamp(entity.mtime).astimezone()
+    return entity.updated_at
+
+
 def get_entity_ids(item: SearchIndexRow) -> set[int]:
     match item.type:
         case SearchItemType.ENTITY:
@@ -97,7 +108,7 @@ async def get_resource_content(
             # Read content for each entity
             content = await file_service.read_entity_content(result)
             memory_url = normalize_memory_url(result.permalink)
-            modified_date = result.updated_at.isoformat()
+            modified_date = _mtime_to_datetime(result).isoformat()
             checksum = result.checksum[:8] if result.checksum else ""
 
             # Prepare the delimited content
diff --git a/src/basic_memory/services/directory_service.py b/src/basic_memory/services/directory_service.py
index 3e504c83..90e6ee76 100644
--- a/src/basic_memory/services/directory_service.py
+++ b/src/basic_memory/services/directory_service.py
@@ -3,7 +3,9 @@
 import fnmatch
 import logging
 import os
+from datetime import datetime
 from typing import Dict, List, Optional, Sequence
+
 import logfire
 
 from basic_memory.models import Entity
@@ -13,6 +15,17 @@ from basic_memory.schemas.directory import DirectoryNode
 logger = logging.getLogger(__name__)
 
 
+def _mtime_to_datetime(entity: Entity) -> datetime:
+    """Convert entity mtime (file modification time) to datetime.
+
+    Returns the file's actual modification time, falling back to updated_at
+    if mtime is not available.
+    """
+    if entity.mtime:
+        return datetime.fromtimestamp(entity.mtime).astimezone()
+    return entity.updated_at
+
+
 class DirectoryService:
     """Service for working with directory trees."""
 
@@ -79,7 +92,7 @@ class DirectoryService:
                 entity_id=file.id,
                 entity_type=file.entity_type,
                 content_type=file.content_type,
-                updated_at=file.updated_at,
+                updated_at=_mtime_to_datetime(file),
             )
 
             # Add to parent directory's children
@@ -245,7 +258,7 @@ class DirectoryService:
                 entity_id=file.id,
                 entity_type=file.entity_type,
                 content_type=file.content_type,
-                updated_at=file.updated_at,
+                updated_at=_mtime_to_datetime(file),
             )
 
             # Add to parent directory's children
diff --git a/src/basic_memory/services/search_service.py b/src/basic_memory/services/search_service.py
index 5dd990ff..44c887fd 100644
--- a/src/basic_memory/services/search_service.py
+++ b/src/basic_memory/services/search_service.py
@@ -17,6 +17,17 @@ from basic_memory.schemas.search import SearchQuery, SearchItemType
 from basic_memory.services import FileService
 
 
+def _mtime_to_datetime(entity: Entity) -> datetime:
+    """Convert entity mtime (file modification time) to datetime.
+
+    Returns the file's actual modification time, falling back to updated_at
+    if mtime is not available.
+    """
+    if entity.mtime:
+        return datetime.fromtimestamp(entity.mtime).astimezone()
+    return entity.updated_at
+
+
 class SearchService:
     """Service for search operations.
 
@@ -200,7 +211,7 @@ class SearchService:
                     "entity_type": entity.entity_type,
                 },
                 created_at=entity.created_at,
-                updated_at=entity.updated_at,
+                updated_at=_mtime_to_datetime(entity),
                 project_id=entity.project_id,
             )
         )
@@ -279,7 +290,7 @@ class SearchService:
                     "entity_type": entity.entity_type,
                 },
                 created_at=entity.created_at,
-                updated_at=entity.updated_at,
+                updated_at=_mtime_to_datetime(entity),
                 project_id=entity.project_id,
             )
         )
@@ -313,7 +324,7 @@ class SearchService:
                         "tags": obs.tags,
                     },
                     created_at=entity.created_at,
-                    updated_at=entity.updated_at,
+                    updated_at=_mtime_to_datetime(entity),
                     project_id=entity.project_id,
                 )
             )
@@ -343,7 +354,7 @@ class SearchService:
                     to_id=rel.to_id,
                     relation_type=rel.relation_type,
                     created_at=entity.created_at,
-                    updated_at=entity.updated_at,
+                    updated_at=_mtime_to_datetime(entity),
                     project_id=entity.project_id,
                 )
             )