diff --git a/memos/cmds/library.py b/memos/cmds/library.py
index c529f80..1c62ba1 100644
--- a/memos/cmds/library.py
+++ b/memos/cmds/library.py
@@ -75,8 +75,14 @@ def ls():
 
 @lib_app.command("create")
 def add(name: str, folders: List[str]):
+    absolute_folders = []
+    for folder in folders:
+        folder_path = Path(folder).resolve()
+        absolute_folders.append({
+            "path": str(folder_path),
+            "last_modified_at": datetime.fromtimestamp(folder_path.stat().st_mtime).isoformat(),
+        })
 
-    absolute_folders = [str(Path(folder).resolve()) for folder in folders]
     response = httpx.post(
         f"{BASE_URL}/libraries",
         json={"name": name, "folders": absolute_folders},
@@ -89,7 +95,14 @@ def add(name: str, folders: List[str]):
 
 @lib_app.command("add-folder")
 def add_folder(library_id: int, folders: List[str]):
-    absolute_folders = [str(Path(folder).resolve()) for folder in folders]
+    absolute_folders = []
+    for folder in folders:
+        folder_path = Path(folder).resolve()
+        absolute_folders.append({
+            "path": str(folder_path),
+            "last_modified_at": datetime.fromtimestamp(folder_path.stat().st_mtime).isoformat(),
+        })
+
     response = httpx.post(
         f"{BASE_URL}/libraries/{library_id}/folders",
         json={"folders": absolute_folders},
diff --git a/memos/commands.py b/memos/commands.py
index a4294d8..c447ff4 100644
--- a/memos/commands.py
+++ b/memos/commands.py
@@ -1,6 +1,7 @@
 import os
 import logging
 from pathlib import Path
+from datetime import datetime
 
 import httpx
 import typer
@@ -97,9 +98,13 @@ def scan_default_library(force: bool = False):
     if not default_library["folders"]:
         # Add the screenshots directory to the library
         screenshots_dir = Path(settings.screenshots_dir).resolve()
+        folder = {
+            "path": str(screenshots_dir),
+            "last_modified_at": datetime.fromtimestamp(screenshots_dir.stat().st_mtime).isoformat(),
+        }
         response = httpx.post(
             f"{BASE_URL}/libraries/{default_library['id']}/folders",
-            json={"folders": [str(screenshots_dir)]},
+            json={"folders": [folder]},
         )
         if response.status_code != 200:
             print(
diff --git a/memos/crud.py b/memos/crud.py
index bffef2d..3392731 100644
--- a/memos/crud.py
+++ b/memos/crud.py
@@ -37,8 +37,13 @@ def create_library(library: NewLibraryParam, db: Session) -> Library:
     db.commit()
     db.refresh(db_library)
 
-    for folder_path in library.folders:
-        db_folder = FolderModel(path=str(folder_path), library_id=db_library.id)
+    for folder in library.folders:
+        db_folder = FolderModel(
+            path=str(folder.path),
+            library_id=db_library.id,
+            last_modified_at=folder.last_modified_at,
+            type=folder.type,
+        )
         db.add(db_folder)
 
     db.commit()
@@ -46,7 +51,12 @@ def create_library(library: NewLibraryParam, db: Session) -> Library:
         id=db_library.id,
         name=db_library.name,
         folders=[
-            Folder(id=db_folder.id, path=db_folder.path)
+            Folder(
+                id=db_folder.id,
+                path=db_folder.path,
+                last_modified_at=db_folder.last_modified_at,
+                type=db_folder.type,
+            )
             for db_folder in db_library.folders
         ],
         plugins=[],
@@ -66,13 +76,16 @@ def get_library_by_name(library_name: str, db: Session) -> Library | None:
 
 
 def add_folders(library_id: int, folders: NewFoldersParam, db: Session) -> Library:
-    db_folders = []
-    for folder_path in folders.folders:
-        db_folder = FolderModel(path=str(folder_path), library_id=library_id)
+    for folder in folders.folders:
+        db_folder = FolderModel(
+            path=str(folder.path),
+            library_id=library_id,
+            last_modified_at=folder.last_modified_at,
+            type=folder.type,
+        )
         db.add(db_folder)
         db.commit()
         db.refresh(db_folder)
-        db_folders.append(Folder(id=db_folder.id, path=db_folder.path))
 
     db_library = db.query(LibraryModel).filter(LibraryModel.id == library_id).first()
     return Library(**db_library.__dict__)
@@ -86,7 +99,9 @@ def create_entity(library_id: int, entity: NewEntityParam, db: Session) -> Entit
     entity.tags = None
     entity.metadata_entries = None
 
-    db_entity = EntityModel(**entity.model_dump(exclude_none=True), library_id=library_id)
+    db_entity = EntityModel(
+        **entity.model_dump(exclude_none=True), library_id=library_id
+    )
     db.add(db_entity)
     db.commit()
     db.refresh(db_entity)
@@ -371,14 +386,19 @@ def update_entity_metadata_entries(
 def get_plugin_by_id(plugin_id: int, db: Session) -> Plugin | None:
     return db.query(PluginModel).filter(PluginModel.id == plugin_id).first()
 
+
 def remove_plugin_from_library(library_id: int, plugin_id: int, db: Session):
-    library_plugin = db.query(LibraryPluginModel).filter(
-        LibraryPluginModel.library_id == library_id,
-        LibraryPluginModel.plugin_id == plugin_id
-    ).first()
-    
+    library_plugin = (
+        db.query(LibraryPluginModel)
+        .filter(
+            LibraryPluginModel.library_id == library_id,
+            LibraryPluginModel.plugin_id == plugin_id,
+        )
+        .first()
+    )
+
     if library_plugin:
         db.delete(library_plugin)
         db.commit()
     else:
-        raise ValueError(f"Plugin {plugin_id} not found in library {library_id}")
\ No newline at end of file
+        raise ValueError(f"Plugin {plugin_id} not found in library {library_id}")
diff --git a/memos/models.py b/memos/models.py
index 7f700f6..5d659d4 100644
--- a/memos/models.py
+++ b/memos/models.py
@@ -13,7 +13,7 @@ from sqlalchemy import (
 from datetime import datetime
 from sqlalchemy.orm import relationship, DeclarativeBase, Mapped, mapped_column, Session
 from typing import List
-from .schemas import MetadataSource, MetadataType
+from .schemas import MetadataSource, MetadataType, FolderType
 from sqlalchemy.exc import OperationalError
 from sqlalchemy.orm import sessionmaker
 from .config import get_database_path, settings
@@ -52,6 +52,12 @@ class FolderModel(Base):
     entities: Mapped[List["EntityModel"]] = relationship(
         "EntityModel", back_populates="folder"
     )
+    type: Mapped[FolderType] = mapped_column(
+        Enum(FolderType), nullable=False
+    )
+    last_modified_at: Mapped[datetime | None] = mapped_column(
+        DateTime, nullable=False
+    )
 
 
 class EntityModel(Base):
diff --git a/memos/schemas.py b/memos/schemas.py
index b1b6042..c406733 100644
--- a/memos/schemas.py
+++ b/memos/schemas.py
@@ -11,6 +11,11 @@ from datetime import datetime
 from enum import Enum
 
 
+class FolderType(Enum):
+    DEFAULT = "default"
+    DUMMY = "dummy"
+
+
 class MetadataSource(Enum):
     USER_GENERATED = "user_generated"
     SYSTEM_GENERATED = "system_generated"
@@ -23,17 +28,19 @@ class MetadataType(Enum):
     NUMBER_DATA = "number"
 
 
-class NewLibraryParam(BaseModel):
-    name: str
-    folders: List[DirectoryPath] = []
-
-
 class NewFolderParam(BaseModel):
     path: DirectoryPath
+    last_modified_at: datetime
+    type: str = FolderType.DEFAULT
+
+
+class NewLibraryParam(BaseModel):
+    name: str
+    folders: List[NewFolderParam] = []
 
 
 class NewFoldersParam(BaseModel):
-    folders: List[DirectoryPath] = []
+    folders: List[NewFolderParam] = []
 
 
 class EntityMetadataParam(BaseModel):
@@ -103,6 +110,8 @@ class NewLibraryPluginParam(BaseModel):
 class Folder(BaseModel):
     id: int
     path: str
+    last_modified_at: datetime
+    type: FolderType
 
     model_config = ConfigDict(from_attributes=True)
 
diff --git a/memos/server.py b/memos/server.py
index f40982e..13f2e99 100644
--- a/memos/server.py
+++ b/memos/server.py
@@ -146,8 +146,14 @@ def new_library(library_param: NewLibraryParam, db: Session = Depends(get_db)):
         )
 
     # Remove duplicate folders from the library_param
-    unique_folders = list(set(library_param.folders))
+    unique_folders = []
+    seen_paths = set()
+    for folder in library_param.folders:
+        if folder.path not in seen_paths:
+            seen_paths.add(folder.path)
+            unique_folders.append(folder)
     library_param.folders = unique_folders
+
     library = crud.create_library(library_param, db)
     return library