diff --git a/gh-pages-template/assets/js/app.js b/gh-pages-template/assets/js/app.js
index 3193410..e6351fb 100644
--- a/gh-pages-template/assets/js/app.js
+++ b/gh-pages-template/assets/js/app.js
@@ -225,7 +225,7 @@ class UIManager {
     formatUpdateTime(isoString) {
         if (!isoString) return '-';
         const date = new Date(isoString);
-        if (isNaN(date.getTime())) return isoString;
+        if (Number.isNaN(date.getTime())) return isoString;
         return date.toLocaleString();
     }