diff --git a/flaschengeist/controller/userController.py b/flaschengeist/controller/userController.py
index b5e427d..9d8b2ac 100644
--- a/flaschengeist/controller/userController.py
+++ b/flaschengeist/controller/userController.py
@@ -2,7 +2,7 @@ import re
 import secrets
 
 from io import BytesIO
-from typing import Optional
+from typing import Optional, Union
 from sqlalchemy import exc
 from sqlalchemy_utils import merge_references
 from datetime import datetime, timedelta, timezone
@@ -262,7 +262,12 @@ def register(data, passwd=None):
     return user
 
 
-def load_avatar(user: User):
+def get_last_modified(user: User):
+    """Get the last modification date of the user"""
+    return get_provider(user.userid).get_last_modified(user)
+
+
+def load_avatar(user: User, etag: Union[str, None] = None):
     if user.avatar_ is not None:
         return imageController.send_image(image=user.avatar_)
     else:
diff --git a/flaschengeist/plugins/__init__.py b/flaschengeist/plugins/__init__.py
index 2907166..23d3783 100644
--- a/flaschengeist/plugins/__init__.py
+++ b/flaschengeist/plugins/__init__.py
@@ -248,6 +248,16 @@ class AuthPlugin(Plugin):
         """
         raise NotImplementedError
 
+    def get_modified_time(self, user):
+        """If backend is using external data, then return the timestamp of the last modification
+
+        Args:
+            user: User object
+        Returns:
+            Timestamp of last modification
+        """
+        pass
+
     def get_avatar(self, user) -> _Avatar:
         """Retrieve avatar for given user (if supported by auth backend)
 
diff --git a/flaschengeist/plugins/auth_ldap/__init__.py b/flaschengeist/plugins/auth_ldap/__init__.py
index db2823a..4574929 100644
--- a/flaschengeist/plugins/auth_ldap/__init__.py
+++ b/flaschengeist/plugins/auth_ldap/__init__.py
@@ -10,6 +10,8 @@ from ldap3.core.exceptions import LDAPPasswordIsMandatoryError, LDAPBindError
 from werkzeug.exceptions import BadRequest, InternalServerError, NotFound
 from werkzeug.datastructures import FileStorage
 
+from datetime import datetime
+
 from flaschengeist import logger
 from flaschengeist.config import config
 from flaschengeist.controller import userController
@@ -158,6 +160,17 @@ class AuthLDAP(AuthPlugin):
         except (LDAPPasswordIsMandatoryError, LDAPBindError):
             raise BadRequest
 
+    def get_modified_time(self, user):
+        self.ldap.connection.search(
+            self.search_dn,
+            "(uid={})".format(user.userid),
+            SUBTREE,
+            attributes=["modifyTimestamp"],
+        )
+        r = self.ldap.connection.response[0]["attributes"]
+        modified_time = r["modifyTimestamp"][0]
+        return datetime.strptime(modified_time, "%Y%m%d%H%M%SZ")
+
     def get_avatar(self, user):
         self.ldap.connection.search(
             self.search_dn,