diff --git a/apps/calendar/apps/web/src/lib/components/calendar/CalendarSidebar.svelte b/apps/calendar/apps/web/src/lib/components/calendar/CalendarSidebar.svelte
index e8dbef1a8..e0b9bf5c5 100644
--- a/apps/calendar/apps/web/src/lib/components/calendar/CalendarSidebar.svelte
+++ b/apps/calendar/apps/web/src/lib/components/calendar/CalendarSidebar.svelte
@@ -1,14 +1,27 @@
 <script lang="ts">
 	import { calendarsStore } from '$lib/stores/calendars.svelte';
+	import { externalCalendarsStore } from '$lib/stores/external-calendars.svelte';
+	import { authStore } from '$lib/stores/auth.svelte';
 	import { goto } from '$app/navigation';
+	import { onMount } from 'svelte';
 
 	function handleToggle(calendarId: string) {
 		calendarsStore.toggleVisibility(calendarId);
 	}
 
+	function handleExternalToggle(id: string, currentVisible: boolean) {
+		externalCalendarsStore.update(id, { isVisible: !currentVisible });
+	}
+
 	function handleAddCalendar() {
 		goto('/settings');
 	}
+
+	onMount(() => {
+		if (authStore.isAuthenticated && externalCalendarsStore.calendars.length === 0) {
+			externalCalendarsStore.fetchCalendars();
+		}
+	});
 </script>
 
 <div class="calendar-sidebar-section">
@@ -41,6 +54,41 @@
 			<p class="empty-message">Keine Kalender vorhanden</p>
 		{/if}
 	</div>
+
+	{#if externalCalendarsStore.calendars.length > 0}
+		<div class="section-header external-header">
+			<h3 class="section-title">Externe Kalender</h3>
+			<button class="add-btn" onclick={() => goto('/settings/sync')} aria-label="Sync verwalten">
+				<svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+					<path
+						stroke-linecap="round"
+						stroke-linejoin="round"
+						stroke-width="2"
+						d="M4 4v5h.582m15.356 2A8.001 8.001 0 004.582 9m0 0H9m11 11v-5h-.581m0 0a8.003 8.003 0 01-15.357-2m15.357 2H15"
+					/>
+				</svg>
+			</button>
+		</div>
+
+		<div class="calendar-list" role="group" aria-label="Externe Kalender Sichtbarkeit">
+			{#each externalCalendarsStore.calendars as cal}
+				<label class="calendar-item">
+					<input
+						type="checkbox"
+						checked={cal.isVisible}
+						onchange={() => handleExternalToggle(cal.id, cal.isVisible)}
+						style="accent-color: {cal.color}"
+						aria-label="{cal.name} {cal.isVisible ? 'sichtbar' : 'ausgeblendet'}"
+					/>
+					<span class="color-dot" style="background-color: {cal.color}" aria-hidden="true"></span>
+					<span class="calendar-name">{cal.name}</span>
+					{#if cal.lastSyncError}
+						<span class="sync-error-dot" title="Sync-Fehler"></span>
+					{/if}
+				</label>
+			{/each}
+		</div>
+	{/if}
 </div>
 
 <style>
@@ -121,4 +169,19 @@
 		text-align: center;
 		padding: 1rem;
 	}
+
+	.external-header {
+		margin-top: 1rem;
+		padding-top: 0.75rem;
+		border-top: 1px solid hsl(var(--color-border));
+	}
+
+	.sync-error-dot {
+		width: 6px;
+		height: 6px;
+		border-radius: 50%;
+		background: hsl(0 84% 60%);
+		flex-shrink: 0;
+		margin-left: auto;
+	}
 </style>
diff --git a/apps/calendar/apps/web/src/lib/components/event/EventDetailModal.svelte b/apps/calendar/apps/web/src/lib/components/event/EventDetailModal.svelte
index 84a6ae38b..ab7ed9feb 100644
--- a/apps/calendar/apps/web/src/lib/components/event/EventDetailModal.svelte
+++ b/apps/calendar/apps/web/src/lib/components/event/EventDetailModal.svelte
@@ -3,8 +3,10 @@
 	import { eventsStore } from '$lib/stores/events.svelte';
 	import { calendarsStore } from '$lib/stores/calendars.svelte';
 	import EventForm from './EventForm.svelte';
+	import RecurrenceEditDialog from './RecurrenceEditDialog.svelte';
 	import { TagBadge, toastStore as toast } from '@manacore/shared-ui';
 	import type { CalendarEvent, UpdateEventInput } from '@calendar/shared';
+	import { describeRecurrence, parseRRule } from '@calendar/shared';
 	import * as api from '$lib/api/events';
 	import { format } from 'date-fns';
 	import { de } from 'date-fns/locale';
@@ -21,6 +23,8 @@
 	let event = $state<CalendarEvent | null>(null);
 	let loading = $state(true);
 	let isEditing = $state(false);
+	let showRecurrenceDialog = $state(false);
+	let recurrenceDialogMode = $state<'edit' | 'delete'>('delete');
 
 	// Load event data
 	$effect(() => {
@@ -60,6 +64,13 @@
 	async function handleDelete() {
 		if (!event) return;
 
+		// For recurring events, show the recurrence dialog
+		if (event.recurrenceRule || eventsStore.isRecurrenceOccurrence(event.id)) {
+			recurrenceDialogMode = 'delete';
+			showRecurrenceDialog = true;
+			return;
+		}
+
 		if (!confirm('Möchten Sie diesen Termin wirklich löschen?')) {
 			return;
 		}
@@ -75,6 +86,21 @@
 		onClose();
 	}
 
+	async function handleRecurrenceAction(action: 'this' | 'all' | 'this_and_future') {
+		if (!event) return;
+		showRecurrenceDialog = false;
+
+		if (recurrenceDialogMode === 'delete') {
+			let result;
+			if (action === 'this') {
+				result = await eventsStore.deleteRecurrenceOccurrence(event.id);
+			} else {
+				result = await eventsStore.deleteRecurrenceSeries(event.id);
+			}
+			if (!result.error) onClose();
+		}
+	}
+
 	function handleCancel() {
 		if (isEditing) {
 			isEditing = false;
@@ -145,6 +171,13 @@
 
 <svelte:window onkeydown={handleKeydown} />
 
+<RecurrenceEditDialog
+	visible={showRecurrenceDialog}
+	mode={recurrenceDialogMode}
+	onSelect={handleRecurrenceAction}
+	onCancel={() => (showRecurrenceDialog = false)}
+/>
+
 <!-- svelte-ignore a11y_click_events_have_key_events a11y_no_static_element_interactions -->
 <div class="modal-backdrop" onclick={handleBackdropClick} role="presentation">
 	<div class="modal-container" role="dialog" aria-modal="true" aria-labelledby="modal-title">
diff --git a/apps/calendar/apps/web/src/lib/components/event/QuickEventOverlay.svelte b/apps/calendar/apps/web/src/lib/components/event/QuickEventOverlay.svelte
index a7e8b4565..8994167fa 100644
--- a/apps/calendar/apps/web/src/lib/components/event/QuickEventOverlay.svelte
+++ b/apps/calendar/apps/web/src/lib/components/event/QuickEventOverlay.svelte
@@ -3,6 +3,7 @@
 	import { eventsStore } from '$lib/stores/events.svelte';
 	import { settingsStore } from '$lib/stores/settings.svelte';
 	import { contactsStore } from '$lib/stores/contacts.svelte';
+	import RecurrenceEditDialog from './RecurrenceEditDialog.svelte';
 	import type {
 		LocationDetails,
 		CalendarEvent,
@@ -207,6 +208,7 @@
 	let locationCity = $state('');
 	let locationCountry = $state('');
 	let submitting = $state(false);
+	let showRecurrenceDialog = $state(false);
 
 	// People state
 	let responsiblePerson = $state<ResponsiblePerson | null>(null);
@@ -605,6 +607,12 @@
 	async function handleDelete() {
 		if (!event) return;
 
+		// For recurring events, show recurrence dialog
+		if (event.recurrenceRule || eventsStore.isRecurrenceOccurrence(event.id)) {
+			showRecurrenceDialog = true;
+			return;
+		}
+
 		submitting = true;
 		try {
 			const result = await eventsStore.deleteEvent(event.id);
@@ -623,6 +631,26 @@
 		}
 	}
 
+	async function handleRecurrenceDeleteAction(action: 'this' | 'all' | 'this_and_future') {
+		if (!event) return;
+		showRecurrenceDialog = false;
+		submitting = true;
+		try {
+			let result;
+			if (action === 'this') {
+				result = await eventsStore.deleteRecurrenceOccurrence(event.id);
+			} else {
+				result = await eventsStore.deleteRecurrenceSeries(event.id);
+			}
+			if (!result.error) {
+				onDeleted?.();
+				onClose();
+			}
+		} finally {
+			submitting = false;
+		}
+	}
+
 	function handleKeydown(e: KeyboardEvent) {
 		if (e.key === 'Escape') {
 			onClose();
@@ -632,6 +660,13 @@
 
 <svelte:window onkeydown={handleKeydown} />
 
+<RecurrenceEditDialog
+	visible={showRecurrenceDialog}
+	mode="delete"
+	onSelect={handleRecurrenceDeleteAction}
+	onCancel={() => (showRecurrenceDialog = false)}
+/>
+
 <!-- Overlay (no blocking backdrop - allows interaction with calendar) -->
 <!-- Portal to body to escape stacking contexts -->
 <div
diff --git a/apps/calendar/docs/COMPLEXITY_AUDIT.md b/apps/calendar/docs/COMPLEXITY_AUDIT.md
index fc74131a6..bf1d26290 100644
--- a/apps/calendar/docs/COMPLEXITY_AUDIT.md
+++ b/apps/calendar/docs/COMPLEXITY_AUDIT.md
@@ -80,15 +80,20 @@ Die Legacy-Composables (`useDragDrop`, `useResize`) sind von keiner Komponente i
 
 ## Teil 2: Unterentwickelte Bereiche
 
-### 1. Keine Kalender-Synchronisation (CalDAV/iCal) — Priorität: Hoch
+### 1. Keine Kalender-Synchronisation (CalDAV/iCal) — ✅ Implementiert
 
-Backend hat `external_calendars`-Tabelle und Sync-Endpunkte. Frontend hat null UI dafür.
-Für eine Kalender-App ist das das größte fehlende Feature.
+- API-Client (`lib/api/sync.ts`) für alle Sync-Endpunkte
+- External Calendars Store mit connect/disconnect/sync
+- Settings-Seite `/settings/sync` mit Provider-Auswahl, CalDAV-Discovery, Sync-Status
+- Sidebar zeigt externe Kalender mit Sichtbarkeits-Toggle
 
-### 2. Keine wiederkehrenden Termine (Recurring Events) — Priorität: Hoch
+### 2. Keine wiederkehrenden Termine (Recurring Events) — ✅ Implementiert
 
-Backend-Schema unterstützt RFC 5545 RRULE. Kein UI oder Store-Logik dafür.
-Essentiell für eine nutzbare Kalender-App.
+- RecurrenceSelector-Komponente mit Presets + benutzerdefinierter Konfiguration
+- Im EventForm integriert, sendet `recurrenceRule` + `recurrenceEndDate`
+- Events Store expandiert RRULE zu Einzelterminen per `generateOccurrences()`
+- RecurrenceEditDialog für "Diesen/Alle/Zukünftige" beim Löschen
+- In EventDetailModal und QuickEventOverlay integriert
 
 ### 3. Erinnerungen / Notifications nur rudimentär — Priorität: Mittel