diff --git a/app/scodoc/sco_undo_notes.py b/app/scodoc/sco_undo_notes.py
index 1268a831..a8da7995 100644
--- a/app/scodoc/sco_undo_notes.py
+++ b/app/scodoc/sco_undo_notes.py
@@ -68,17 +68,18 @@ class NotesOperation(dict):
     Keys: evaluation_id, date, uid, notes
     """
 
-    def get_comment(self):
+    def get_comment(self) -> str:
+        "le commentaire ou une chaine vide"
         if self["notes"]:
             return self["notes"][0]["comment"]
-        else:
-            return ""
+        return ""
 
     def comp_values(self):
         "compute keys: comment, nb_notes"
         self["comment"] = self.get_comment()
         self["nb_notes"] = len(self["notes"])
-        self["datestr"] = self["date"].strftime("%a %d/%m/%y %Hh%M")
+        self["date_str"] = self["date"].strftime("%a %d/%m/%y %Hh%M")
+        self["_date_str_order"] = self["date"].isoformat()
 
     def undo(self):
         "undo operation"
@@ -113,12 +114,12 @@ def list_operations(evaluation_id):
         ).values()
     )
     dt = OPERATION_DATE_TOLERANCE
-    NotesDates = {}  # { uid : intervalmap }
+    notes_dates = {}  # { uid : intervalmap }
 
     for note in notes + notes_log:
-        if note["uid"] not in NotesDates:
-            NotesDates[note["uid"]] = intervalmap()
-        nd = NotesDates[note["uid"]]
+        if note["uid"] not in notes_dates:
+            notes_dates[note["uid"]] = intervalmap()
+        nd = notes_dates[note["uid"]]
         if nd[note["date"]] is None:
             nd[note["date"] - dt : note["date"] + dt] = [note]
         else:
@@ -128,32 +129,32 @@ def list_operations(evaluation_id):
     for note in notes:
         current_notes_by_etud[note["etudid"]] = note
 
-    Ops = []
-    for uid in NotesDates.keys():
+    operations = []
+    for uid, note_date in notes_dates.items():
         user_name = "{prenomnom} ({user_name})".format(**sco_users.user_info(uid))
-        for (t0, _), notes in NotesDates[uid].items():
-            Op = NotesOperation(
+        for (t0, _), notes in note_date.items():
+            operation = NotesOperation(
                 evaluation_id=evaluation_id,
                 date=t0,
                 uid=uid,
                 user_name=user_name,
-                notes=NotesDates[uid][t0],
+                notes=note_date[t0],
                 current_notes_by_etud=current_notes_by_etud,
             )
-            Op.comp_values()
-            Ops.append(Op)
+            operation.comp_values()
+            operations.append(operation)
 
-    return Ops
+    return operations
 
 
-def evaluation_list_operations(evaluation_id):
+def evaluation_list_operations(evaluation_id: int):
     """Page listing operations on evaluation"""
     evaluation = Evaluation.get_evaluation(evaluation_id)
     operations = list_operations(evaluation_id)
 
-    columns_ids = ("datestr", "user_name", "nb_notes", "comment")
+    columns_ids = ("date_str", "user_name", "nb_notes", "comment")
     titles = {
-        "datestr": "Date",
+        "date_str": "Date",
         "user_name": "Enseignant",
         "nb_notes": "Nb de notes",
         "comment": "Commentaire",