diff --git a/static/js/upcoming.js b/static/js/upcoming.js
index f031b4d..b172d83 100644
--- a/static/js/upcoming.js
+++ b/static/js/upcoming.js
@@ -1,5 +1,17 @@
 import ICAL from "https://unpkg.com/ical.js/dist/ical.min.js";
 
+/**
+ * Read the URL of an event.
+ *
+ * ICAL.Event does not expose the URL property, so read it from the component.
+ *
+ * @param {ICAL.Event} event The event to read the URL of
+ * @returns {string} The URL, empty when the event has none
+ */
+function eventUrl(event) {
+  return event.component.getFirstPropertyValue("url") ?? "";
+}
+
 /**
  * Parse an ICS calendar and return upcoming event occurrences.
  *
@@ -21,12 +33,15 @@ function getUpcomingEvents(icsText, now, maxEvents, maxDays) {
   for (const component of calendar.getAllSubcomponents("vevent")) {
     const event = new ICAL.Event(component);
 
-    if (!event.startDate) {
+    // Occurrences modified via RECURRENCE-ID are reached through the event they
+    // belong to, listing them here as well would show them twice.
+    if (event.isRecurrenceException()) {
       continue;
     }
 
-    // ICAL.Event does not expose the URL property, so read it from the component.
-    const url = component.getFirstPropertyValue("url") ?? "";
+    if (!event.startDate) {
+      continue;
+    }
 
     if (event.isRecurring()) {
       const iterator = event.iterator();
@@ -44,15 +59,16 @@ function getUpcomingEvents(icsText, now, maxEvents, maxDays) {
           break;
         }
 
-        // Details resolve the times of occurrences overridden by RECURRENCE-ID.
+        // Details resolve time, name and URL of an occurrence that was
+        // modified via RECURRENCE-ID.
         const details = event.getOccurrenceDetails(occurrence);
 
         // A running event stays listed until it is over, so filter on its end.
         if (details.endDate.toJSDate() > now) {
           events.push({
             start: details.startDate.toJSDate(),
-            name: event.summary ?? "",
-            url,
+            name: details.item.summary ?? "",
+            url: eventUrl(details.item),
           });
         }
       }
@@ -63,7 +79,7 @@ function getUpcomingEvents(icsText, now, maxEvents, maxDays) {
         events.push({
           start,
           name: event.summary ?? "",
-          url,
+          url: eventUrl(event),
         });
       }
     }