Only process dates with valid dateTime attributes

static/scripts/relativetime.js

@@ -2,9 +2,11 @@
 
 Array.from(document.getElementsByClassName("relative-timestamp")).forEach(
   function (timestamp) {
+    if (timestamp?.dateTime) {
       timestamp.innerText = new Intl.DateTimeFormat(undefined, {
         dateStyle: "long",
         timeStyle: "short",
       }).format(new Date(timestamp.dateTime));
     }
+  }
 );