diff --git a/app/services/qualys_service.py b/app/services/qualys_service.py
index a0ece44..f73092f 100644
--- a/app/services/qualys_service.py
+++ b/app/services/qualys_service.py
@@ -586,9 +586,10 @@ def _refresh_all_agents_impl(db, mode="diff"):
                 pass
 
     # Sauve immediatement le timestamp de DEBUT (couvre annulation en cours)
+    # Format Qualys QPS: YYYY-MM-DDTHH:MM:SSZ (sans microsec)
     if mode == "diff":
         try:
-            start_iso = datetime.now(timezone.utc).isoformat()
+            start_iso = datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
             set_secret(db, "qualys_last_diff_sync", start_iso, "Timestamp dernier sync Qualys diff (debut)")
             db.commit()
         except Exception:
@@ -774,10 +775,10 @@ def _refresh_all_agents_impl(db, mode="diff"):
     stats["ok"] = True
     stats["mode"] = mode
     stats["msg"] = f"[{mode}] {stats['created']} créés, {stats['updated']} mis à jour ({stats['pages']} pages, {stats['errors']} erreurs, {len(tag_filters)} filtres)"
-    # Memorise le timestamp pour le prochain diff sync
+    # Memorise le timestamp pour le prochain diff sync (format sans microsec)
     if mode == "diff":
         try:
-            now_iso = datetime.now(timezone.utc).isoformat()
+            now_iso = datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
             set_secret(db, "qualys_last_diff_sync", now_iso, "Timestamp dernier sync Qualys diff")
             db.commit()
         except Exception: