diff --git a/apps/calendar/apps/web/src/lib/api/base-client.ts b/apps/calendar/apps/web/src/lib/api/base-client.ts
index eafbc7f5f..f2d3ff1ff 100644
--- a/apps/calendar/apps/web/src/lib/api/base-client.ts
+++ b/apps/calendar/apps/web/src/lib/api/base-client.ts
@@ -84,6 +84,7 @@ export function createApiClient(config: ApiClientConfig) {
 			return { data, error: null };
 		} catch (error) {
 			clearTimeout(timeoutId);
+			console.error('[BaseClient] Fetch error:', error);
 
 			if (error instanceof Error && error.name === 'AbortError') {
 				return {
@@ -105,7 +106,7 @@ export function createApiClient(config: ApiClientConfig) {
 /**
  * Helper to build query strings from object
  */
-export function buildQueryString<T extends object>(params: T): string {
+export function buildQueryString(params: Record<string, unknown>): string {
 	const searchParams = new URLSearchParams();
 	Object.entries(params).forEach(([key, value]) => {
 		if (value !== undefined && value !== null) {
diff --git a/apps/calendar/apps/web/src/lib/api/todos.ts b/apps/calendar/apps/web/src/lib/api/todos.ts
index 6f11e576c..f356b8d6f 100644
--- a/apps/calendar/apps/web/src/lib/api/todos.ts
+++ b/apps/calendar/apps/web/src/lib/api/todos.ts
@@ -167,7 +167,7 @@ const fetchTodoApi = todoClient.fetchApi;
 export async function getTasks(
 	query: TaskQuery = {}
 ): Promise<{ data: Task[] | null; error: Error | null }> {
-	const queryString = buildQueryString(query);
+	const queryString = buildQueryString(query as Record<string, unknown>);
 	const result = await fetchTodoApi<TasksResponse>(`/tasks${queryString}`);
 	return {
 		data: result.data?.tasks || null,
@@ -242,7 +242,9 @@ export async function uncompleteTask(
 }
 
 export async function getTodayTasks(): Promise<{ data: Task[] | null; error: Error | null }> {
+	console.log('[TodoAPI] Fetching /tasks/today from:', TODO_API_BASE);
 	const result = await fetchTodoApi<TasksResponse>('/tasks/today');
+	console.log('[TodoAPI] Response:', result);
 	return {
 		data: result.data?.tasks || null,
 		error: result.error,
diff --git a/apps/calendar/apps/web/src/lib/components/calendar/DayView.svelte b/apps/calendar/apps/web/src/lib/components/calendar/DayView.svelte
index 30c398603..7ad07179d 100644
--- a/apps/calendar/apps/web/src/lib/components/calendar/DayView.svelte
+++ b/apps/calendar/apps/web/src/lib/components/calendar/DayView.svelte
@@ -75,8 +75,11 @@
 	);
 
 	// Get display mode for an event (per-event override takes precedence over global setting)
-	function getEventDisplayMode(event: any): 'header' | 'block' {
-		return event.metadata?.allDayDisplayMode || settingsStore.allDayDisplayMode;
+	function getEventDisplayMode(event: CalendarEvent): 'header' | 'block' {
+		return (
+			(event.metadata as { allDayDisplayMode?: 'header' | 'block' } | null)?.allDayDisplayMode ||
+			settingsStore.allDayDisplayMode
+		);
 	}
 
 	// Split all-day events by display mode
@@ -90,7 +93,7 @@
 	// Drag & Drop State
 	// ============================================================================
 	let isDragging = $state(false);
-	let draggedEvent = $state<any>(null);
+	let draggedEvent = $state<CalendarEvent | null>(null);
 	let dragOffsetMinutes = $state(0);
 	let dragPreviewTop = $state(0);
 	let dragPreviewHeight = $state(0);
@@ -100,7 +103,7 @@
 	// Resize State
 	// ============================================================================
 	let isResizing = $state(false);
-	let resizeEvent = $state<any>(null);
+	let resizeEvent = $state<CalendarEvent | null>(null);
 	let resizeEdge = $state<'top' | 'bottom'>('bottom');
 	let resizeOriginalStart = $state<Date | null>(null);
 	let resizeOriginalEnd = $state<Date | null>(null);
@@ -132,7 +135,7 @@
 	// ============================================================================
 	// Drag Handlers
 	// ============================================================================
-	function startDrag(event: any, e: PointerEvent) {
+	function startDrag(event: CalendarEvent, e: PointerEvent) {
 		e.preventDefault();
 		e.stopPropagation();
 
@@ -218,7 +221,7 @@
 	// ============================================================================
 	// Resize Handlers
 	// ============================================================================
-	function startResize(event: any, edge: 'top' | 'bottom', e: PointerEvent) {
+	function startResize(event: CalendarEvent, edge: 'top' | 'bottom', e: PointerEvent) {
 		e.preventDefault();
 		e.stopPropagation();
 
@@ -345,7 +348,7 @@
 	// ============================================================================
 	// Event Styling
 	// ============================================================================
-	function getEventStyle(event: any) {
+	function getEventStyle(event: CalendarEvent) {
 		const start = typeof event.startTime === 'string' ? parseISO(event.startTime) : event.startTime;
 		const end = typeof event.endTime === 'string' ? parseISO(event.endTime) : event.endTime;
 
@@ -459,6 +462,7 @@
 				{@const isBeingDragged = isDragging && draggedEvent?.id === event.id}
 				{@const isBeingResized = isResizing && resizeEvent?.id === event.id}
 				{@const isDraft = eventsStore.isDraftEvent(event.id)}
+				<!-- svelte-ignore a11y_click_events_have_key_events -->
 				<div
 					class="event-card"
 					class:dragging={isBeingDragged}
@@ -481,6 +485,7 @@
 						onpointerdown={(e) => startResize(event, 'top', e)}
 						role="slider"
 						aria-label="Startzeit ändern"
+						aria-valuenow={0}
 						tabindex="-1"
 					></div>
 
@@ -505,6 +510,7 @@
 						onpointerdown={(e) => startResize(event, 'bottom', e)}
 						role="slider"
 						aria-label="Endzeit ändern"
+						aria-valuenow={0}
 						tabindex="-1"
 					></div>
 				</div>
diff --git a/apps/calendar/apps/web/src/lib/components/calendar/MonthView.svelte b/apps/calendar/apps/web/src/lib/components/calendar/MonthView.svelte
index e3bd719f1..ce714fa6f 100644
--- a/apps/calendar/apps/web/src/lib/components/calendar/MonthView.svelte
+++ b/apps/calendar/apps/web/src/lib/components/calendar/MonthView.svelte
@@ -80,7 +80,7 @@
 	// Drag & Drop State
 	// ============================================================================
 	let isDragging = $state(false);
-	let draggedEvent = $state<any>(null);
+	let draggedEvent = $state<CalendarEvent | null>(null);
 	let dragTargetDay = $state<Date | null>(null);
 	let monthViewRef = $state<HTMLElement | null>(null);
 
@@ -286,6 +286,7 @@
 							{#each getEventsForDay(day) as event}
 								{@const isBeingDragged = isDragging && draggedEvent?.id === event.id}
 								{@const isDraft = eventsStore.isDraftEvent(event.id)}
+								<!-- svelte-ignore a11y_click_events_have_key_events -->
 								<div
 									class="event-pill"
 									class:dragging={isBeingDragged}
diff --git a/apps/calendar/apps/web/src/lib/components/calendar/MultiDayView.svelte b/apps/calendar/apps/web/src/lib/components/calendar/MultiDayView.svelte
index 8b5be974e..9b94e347b 100644
--- a/apps/calendar/apps/web/src/lib/components/calendar/MultiDayView.svelte
+++ b/apps/calendar/apps/web/src/lib/components/calendar/MultiDayView.svelte
@@ -96,7 +96,7 @@
 
 	// ========== Drag & Drop State ==========
 	let isDragging = $state(false);
-	let draggedEvent = $state<any>(null);
+	let draggedEvent = $state<CalendarEvent | null>(null);
 	let dragOffsetMinutes = $state(0);
 	let dragTargetDay = $state<Date | null>(null);
 	let dragPreviewTop = $state(0);
@@ -104,7 +104,7 @@
 
 	// ========== Resize State ==========
 	let isResizing = $state(false);
-	let resizeEvent = $state<any>(null);
+	let resizeEvent = $state<CalendarEvent | null>(null);
 	let resizeEdge = $state<'top' | 'bottom'>('bottom');
 	let resizeOriginalStart = $state<Date | null>(null);
 	let resizeOriginalEnd = $state<Date | null>(null);
@@ -126,8 +126,11 @@
 	}
 
 	// Get display mode for an event (per-event override takes precedence over global setting)
-	function getEventDisplayMode(event: any): 'header' | 'block' {
-		return event.metadata?.allDayDisplayMode || settingsStore.allDayDisplayMode;
+	function getEventDisplayMode(event: CalendarEvent): 'header' | 'block' {
+		return (
+			(event.metadata as { allDayDisplayMode?: 'header' | 'block' } | null)?.allDayDisplayMode ||
+			settingsStore.allDayDisplayMode
+		);
 	}
 
 	// Split all-day events by display mode
@@ -144,7 +147,7 @@
 		days.some((day) => getHeaderAllDayEventsForDay(day).length > 0)
 	);
 
-	function getEventStyle(event: any) {
+	function getEventStyle(event: CalendarEvent) {
 		const start = typeof event.startTime === 'string' ? parseISO(event.startTime) : event.startTime;
 		const end = typeof event.endTime === 'string' ? parseISO(event.endTime) : event.endTime;
 
@@ -225,7 +228,7 @@
 		return Math.round(totalMinutes / MINUTES_PER_SLOT) * MINUTES_PER_SLOT;
 	}
 
-	function startDrag(event: any, e: PointerEvent) {
+	function startDrag(event: CalendarEvent, e: PointerEvent) {
 		e.preventDefault();
 		e.stopPropagation();
 
@@ -328,7 +331,7 @@
 
 	// ========== Resize Functions ==========
 
-	function startResize(event: any, edge: 'top' | 'bottom', e: PointerEvent) {
+	function startResize(event: CalendarEvent, edge: 'top' | 'bottom', e: PointerEvent) {
 		e.preventDefault();
 		e.stopPropagation();
 
@@ -573,6 +576,7 @@
 								onpointerdown={(e) => startResize(event, 'top', e)}
 								role="slider"
 								aria-label="Startzeit ändern"
+								aria-valuenow={0}
 								tabindex="-1"
 							></div>
 
@@ -589,13 +593,14 @@
 								onpointerdown={(e) => startResize(event, 'bottom', e)}
 								role="slider"
 								aria-label="Endzeit ändern"
+								aria-valuenow={0}
 								tabindex="-1"
 							></div>
 						</div>
 					{/each}
 
 					<!-- Drag preview ghost (for cross-day dragging) -->
-					{#if isDragging && draggedEvent && dragTargetDay && isSameDay(day, dragTargetDay) && !getEventsForDay(day).some((e) => e.id === draggedEvent.id)}
+					{#if isDragging && draggedEvent && dragTargetDay && isSameDay(day, dragTargetDay) && !getEventsForDay(day).some((e) => e.id === draggedEvent!.id)}
 						<div
 							class="event-card drag-ghost"
 							style="top: {dragPreviewTop}%; height: {dragPreviewHeight}%; background-color: {calendarsStore.getColor(
diff --git a/apps/calendar/apps/web/src/lib/components/calendar/WeekView.svelte b/apps/calendar/apps/web/src/lib/components/calendar/WeekView.svelte
index 4b7dd667a..29086ce7e 100644
--- a/apps/calendar/apps/web/src/lib/components/calendar/WeekView.svelte
+++ b/apps/calendar/apps/web/src/lib/components/calendar/WeekView.svelte
@@ -97,7 +97,7 @@
 
 	// Drag & Drop State
 	let isDragging = $state(false);
-	let draggedEvent = $state<any>(null);
+	let draggedEvent = $state<CalendarEvent | null>(null);
 	let dragOffsetMinutes = $state(0);
 	let dragTargetDay = $state<Date | null>(null);
 	let dragPreviewTop = $state(0);
@@ -105,7 +105,7 @@
 
 	// Resize State
 	let isResizing = $state(false);
-	let resizeEvent = $state<any>(null);
+	let resizeEvent = $state<CalendarEvent | null>(null);
 	let resizeEdge = $state<'top' | 'bottom'>('bottom');
 	let resizeOriginalStart = $state<Date | null>(null);
 	let resizeOriginalEnd = $state<Date | null>(null);
@@ -127,8 +127,11 @@
 	}
 
 	// Get display mode for an event (per-event override takes precedence over global setting)
-	function getEventDisplayMode(event: any): 'header' | 'block' {
-		return event.metadata?.allDayDisplayMode || settingsStore.allDayDisplayMode;
+	function getEventDisplayMode(event: CalendarEvent): 'header' | 'block' {
+		return (
+			(event.metadata as { allDayDisplayMode?: 'header' | 'block' } | null)?.allDayDisplayMode ||
+			settingsStore.allDayDisplayMode
+		);
 	}
 
 	// Split all-day events by display mode
@@ -145,7 +148,7 @@
 		days.some((day) => getHeaderAllDayEventsForDay(day).length > 0)
 	);
 
-	function getEventStyle(event: any) {
+	function getEventStyle(event: CalendarEvent) {
 		const start = typeof event.startTime === 'string' ? parseISO(event.startTime) : event.startTime;
 		const end = typeof event.endTime === 'string' ? parseISO(event.endTime) : event.endTime;
 
@@ -227,7 +230,7 @@
 		return Math.round(totalMinutes / MINUTES_PER_SLOT) * MINUTES_PER_SLOT;
 	}
 
-	function startDrag(event: any, e: PointerEvent) {
+	function startDrag(event: CalendarEvent, e: PointerEvent) {
 		e.preventDefault();
 		e.stopPropagation();
 
@@ -330,7 +333,7 @@
 
 	// ========== Resize Functions ==========
 
-	function startResize(event: any, edge: 'top' | 'bottom', e: PointerEvent) {
+	function startResize(event: CalendarEvent, edge: 'top' | 'bottom', e: PointerEvent) {
 		e.preventDefault();
 		e.stopPropagation();
 
@@ -595,6 +598,7 @@
 								onpointerdown={(e) => startResize(event, 'top', e)}
 								role="slider"
 								aria-label={$_('event.changeStartTime')}
+								aria-valuenow={0}
 								tabindex="-1"
 							></div>
 
@@ -611,13 +615,14 @@
 								onpointerdown={(e) => startResize(event, 'bottom', e)}
 								role="slider"
 								aria-label={$_('event.changeEndTime')}
+								aria-valuenow={0}
 								tabindex="-1"
 							></div>
 						</div>
 					{/each}
 
 					<!-- Drag preview ghost (for cross-day dragging) -->
-					{#if isDragging && draggedEvent && dragTargetDay && isSameDay(day, dragTargetDay) && !getEventsForDay(day).some((e) => e.id === draggedEvent.id)}
+					{#if isDragging && draggedEvent && dragTargetDay && isSameDay(day, dragTargetDay) && !getEventsForDay(day).some((e) => e.id === draggedEvent!.id)}
 						<div
 							class="event-card drag-ghost"
 							style="top: {dragPreviewTop}%; height: {dragPreviewHeight}%; background-color: {calendarsStore.getColor(
diff --git a/apps/calendar/apps/web/src/lib/stores/events.svelte.ts b/apps/calendar/apps/web/src/lib/stores/events.svelte.ts
index 4de831a64..9578f7870 100644
--- a/apps/calendar/apps/web/src/lib/stores/events.svelte.ts
+++ b/apps/calendar/apps/web/src/lib/stores/events.svelte.ts
@@ -147,15 +147,22 @@ export const eventsStore = {
 	},
 
 	/**
-	 * Delete an event
+	 * Delete an event (optimistic update)
 	 */
 	async deleteEvent(id: string) {
+		// Optimistic: remove event immediately
+		const eventToDelete = events.find((e) => e.id === id);
+		events = events.filter((e) => e.id !== id);
+
 		const result = await api.deleteEvent(id);
 
 		if (result.error) {
+			// Rollback: restore the event on error
+			if (eventToDelete) {
+				events = [...events, eventToDelete];
+			}
 			toastStore.error(`Termin konnte nicht gelöscht werden: ${result.error.message}`);
 		} else {
-			events = events.filter((e) => e.id !== id);
 			toastStore.success('Termin gelöscht');
 		}
 
diff --git a/apps/calendar/apps/web/src/lib/stores/todos.svelte.ts b/apps/calendar/apps/web/src/lib/stores/todos.svelte.ts
index 1311d0971..768b4d4e9 100644
--- a/apps/calendar/apps/web/src/lib/stores/todos.svelte.ts
+++ b/apps/calendar/apps/web/src/lib/stores/todos.svelte.ts
@@ -242,9 +242,12 @@ export const todosStore = {
 		loading = true;
 		error = null;
 
+		console.log('[TodoStore] Fetching today todos...');
 		const result = await api.getTodayTasks();
+		console.log('[TodoStore] Result:', result);
 
 		if (result.error) {
+			console.error('[TodoStore] Error fetching todos:', result.error);
 			error = result.error.message;
 			serviceAvailable = false;
 		} else {
@@ -267,11 +270,18 @@ export const todosStore = {
 		loading = true;
 		error = null;
 
+		console.log('[TodoStore] Fetching upcoming todos...');
 		const result = await api.getUpcomingTasks();
+		console.log('[TodoStore] Upcoming result:', result);
 
 		if (result.error) {
+			console.error('[TodoStore] Error fetching upcoming:', result.error);
 			error = result.error.message;
-			serviceAvailable = false;
+			// Only set serviceAvailable to false if we have no todos yet
+			// (if fetchTodayTodos succeeded, we should still show the service as available)
+			if (todos.length === 0) {
+				serviceAvailable = false;
+			}
 		} else {
 			// Merge with existing todos (avoid duplicates)
 			const newTodos = result.data || [];
@@ -338,13 +348,20 @@ export const todosStore = {
 	},
 
 	/**
-	 * Delete a todo
+	 * Delete a todo (optimistic update)
 	 */
 	async deleteTodo(id: string) {
+		// Optimistic: remove todo immediately
+		const todoToDelete = todos.find((t) => t.id === id);
+		todos = todos.filter((t) => t.id !== id);
+
 		const result = await api.deleteTask(id);
 
-		if (!result.error) {
-			todos = todos.filter((t) => t.id !== id);
+		if (result.error) {
+			// Rollback: restore the todo on error
+			if (todoToDelete) {
+				todos = [...todos, todoToDelete];
+			}
 		}
 
 		return result;
diff --git a/apps/calendar/apps/web/src/lib/utils/eventDateHelpers.ts b/apps/calendar/apps/web/src/lib/utils/eventDateHelpers.ts
new file mode 100644
index 000000000..9e8063377
--- /dev/null
+++ b/apps/calendar/apps/web/src/lib/utils/eventDateHelpers.ts
@@ -0,0 +1,41 @@
+/**
+ * Event Date Helpers
+ * Utilities for consistent date handling across the calendar app
+ */
+
+import { parseISO } from 'date-fns';
+
+/**
+ * Convert a date value that may be either a string or Date to a Date object
+ * This handles the common pattern where API returns ISO strings but we need Date objects
+ */
+export function toDate(value: string | Date): Date {
+	return typeof value === 'string' ? parseISO(value) : value;
+}
+
+/**
+ * Get the start time of an event as a Date object
+ */
+export function getEventStart(event: { startTime: string | Date }): Date {
+	return toDate(event.startTime);
+}
+
+/**
+ * Get the end time of an event as a Date object
+ */
+export function getEventEnd(event: { endTime: string | Date }): Date {
+	return toDate(event.endTime);
+}
+
+/**
+ * Get both start and end times of an event as Date objects
+ */
+export function getEventTimes(event: { startTime: string | Date; endTime: string | Date }): {
+	start: Date;
+	end: Date;
+} {
+	return {
+		start: toDate(event.startTime),
+		end: toDate(event.endTime),
+	};
+}