fix(notdienst): resolve timezone offset mismatch in plan generation

src/app/dashboard/notdienst/plan/actions.ts

@@ -33,8 +33,8 @@ export async function generatePlanAction() {
     where: {
       kitaId,
       date: {
-        gte: new Date(targetYear, targetMonth - 1, 1),
-        lt: new Date(targetYear, targetMonth, 1),
+        gte: new Date(Date.UTC(targetYear, targetMonth - 1, 1)),
+        lt: new Date(Date.UTC(targetYear, targetMonth, 1)),
       },
     },
     include: { child: { select: { familyId: true } } },
@@ -141,7 +141,8 @@ export async function updateAssignmentAction(
   const session = await requireRole([UserRole.ADMIN, UserRole.KOORDINATOR]);
   const kitaId = session.user.kitaId!;
 
-  const parsedDate = new Date(date);
+  const [yr, mo, dy] = date.slice(0, 10).split("-").map(Number);
+  const parsedDate = new Date(Date.UTC(yr, mo - 1, dy));
 
   try {
     await prisma.$transaction(async (tx) => {

src/app/dashboard/notdienst/plan/plan-view.tsx

@@ -121,7 +121,8 @@ export function PlanView({ planId, status, days, allChildren }: PlanViewProps) {
         </div>
         <div className="divide-y">
           {days.map((day) => {
-            const dateObj = new Date(day.date);
+            const [yr, mo, dy] = day.date.slice(0, 10).split("-").map(Number);
+            const dateObj = new Date(yr, mo - 1, dy);
             const isUnbesetzt = !day.childId;
 
             return (

src/lib/date-utils.ts

@@ -1,13 +1,8 @@
 import {
   addMonths,
-  endOfMonth,
   getDate,
   getYear,
   getMonth,
-  isWeekend,
-  eachDayOfInterval,
-  startOfMonth,
-  startOfDay,
   format,
 } from "date-fns";
 import { de } from "date-fns/locale";
@@ -36,13 +31,28 @@ export function getTargetMonthData(now = new Date()) {
 }
 
 export function getWorkingDaysOfMonth(year: number, month: number) {
-  // month ist 1-12, Date erwartet 0-11
-  const start = startOfMonth(new Date(year, month - 1));
-  const end = endOfMonth(start);
+  const start = new Date(Date.UTC(year, month - 1, 1));
+  const end = new Date(Date.UTC(year, month, 0)); // last day of month
 
-  const days = eachDayOfInterval({ start, end });
-  
-  return days
-    .filter((day) => !isWeekend(day))
-    .map((day) => startOfDay(day));
+  const days: Date[] = [];
+  const current = new Date(start);
+  while (current <= end) {
+    const dayOfWeek = current.getUTCDay(); // 0 is Sunday, 6 is Saturday
+    if (dayOfWeek !== 0 && dayOfWeek !== 6) {
+      days.push(new Date(current));
+    }
+    current.setUTCDate(current.getUTCDate() + 1);
+  }
+  return days;
+}
+
+export function formatDateKey(date: Date) {
+  return format(date, "yyyy-MM-dd");
+}
+
+export function formatUtcDateKey(date: Date) {
+  const yyyy = date.getUTCFullYear();
+  const mm = String(date.getUTCMonth() + 1).padStart(2, "0");
+  const dd = String(date.getUTCDate()).padStart(2, "0");
+  return `${yyyy}-${mm}-${dd}`;
 }