diff --git a/package.json b/package.json
index 4993532..3b94904 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "my-weekly-todo-list",
-  "version": "1.57.3",
+  "version": "1.57.4",
   "description": "A web-based weekly task management application that organizes to-dos and calendar events in a single, intuitive weekly view",
   "main": "index.js",
   "scripts": {
diff --git a/src/lib/calendar-events.ts b/src/lib/calendar-events.ts
index b31deb2..0443485 100644
--- a/src/lib/calendar-events.ts
+++ b/src/lib/calendar-events.ts
@@ -518,8 +518,22 @@ export const getCalendarEvents = async (
                 attachments: event.attachments as EventAttachment[] || undefined,
               };
             }));
-          } catch (calError) {
-            console.error(`[CALENDAR] Synology: error fetching events from calendar ${calendarId}:`, calError);
+          } catch (calError: any) {
+            const msg = calError?.message || '';
+            if (msg.includes('not found') || msg.includes('Not found') || calError?.status === 404) {
+              console.warn(`[CALENDAR] Synology: calendar ${calendarId} not found, removing from stored list`);
+              calendars = calendars.filter((c: any) => c.id !== calendarId);
+              try {
+                await prisma.calendarConnection.update({
+                  where: { id: connection.id },
+                  data: { calendars: calendars },
+                });
+              } catch (dbErr) {
+                console.error('[CALENDAR] Synology: failed to prune calendar from DB:', dbErr);
+              }
+            } else {
+              console.error(`[CALENDAR] Synology: error fetching events from calendar ${calendarId}:`, calError);
+            }
           }
         }
       } else if (connection.provider === 'outlook') {
diff --git a/src/lib/synology-calendar.ts b/src/lib/synology-calendar.ts
index d24608a..4a57dbd 100644
--- a/src/lib/synology-calendar.ts
+++ b/src/lib/synology-calendar.ts
@@ -372,8 +372,13 @@ export const getUpcomingEvents = async (
   } catch (error: any) {
     const msg = error?.message || '';
     const status = error?.response?.status || error?.status;
-    // Silently handle expected failures (stale/deleted calendars, permission issues)
-    if (status === 405 || status === 404 || msg.includes('405') || msg.includes('Not Allowed') || msg.includes('not found')) {
+    // Re-throw 404 so callers can prune deleted calendars
+    if (status === 404 || msg.includes('not found') || msg.includes('Calendar not found')) {
+      console.warn(`[SYNOLOGY CALENDAR] Calendar not found: ${calendarUrl}`);
+      throw error;
+    }
+    // Silently handle other expected failures (permission issues, method not allowed)
+    if (status === 405 || msg.includes('405') || msg.includes('Not Allowed')) {
       console.warn(`[SYNOLOGY CALENDAR] Calendar unavailable (${status || msg.slice(0, 60)}): ${calendarUrl}`);
     } else {
       console.error(`[SYNOLOGY CALENDAR] Error fetching events for ${calendarUrl}:`, error);