bugfix: appointment hours now use the client timezone on UTC servers.

Logical API errors throw stable codes so users see translated messages instead of a generic bad request.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/ui/treatment/LabCasesDispatchPanel.tsx

@@ -20,6 +20,7 @@ import { prosthesisTypeColorFromCatalog } from '@/components/treatment/prosthesi
 import type { ProsthesisCatalogEntry, TreatmentCatalogEntry } from '@/types/treatment-catalog';
 import type { LabCaseDraft, LinkedOrganizationOption, TreatmentDetailDraft } from '@/types/treatment';
 import type { PatientLabCaseSummary } from '@/types/lab-case-activity';
+import { getUserFacingError } from '@/components/shared/formatApiError';
 import { groupsFromFlatTeeth } from '@/components/treatment/toothSelectionGroups';
 
 interface LabCasesDispatchPanelProps {
@@ -124,6 +125,7 @@ export function LabCasesDispatchPanel({
   onCommentError,
 }: LabCasesDispatchPanelProps) {
   const t = useTranslations('treatment');
+  const tErrors = useTranslations('errors');
   const [prosthesisOptions, setProsthesisOptions] = useState<ProsthesisCatalogEntry[]>([]);
   const [applyAllProsthesis, setApplyAllProsthesis] = useState('');
   const [pendingComment, setPendingComment] = useState('');
@@ -273,7 +275,7 @@ export function LabCasesDispatchPanel({
         taskProgress: response.data.taskProgress ?? activeLabCase.taskProgress,
       });
     } catch (error) {
-      onCommentError?.(error instanceof Error ? error.message : t('dueDateUpdateError'));
+      onCommentError?.(getUserFacingError(error, tErrors, t('dueDateUpdateError')));
     }
   }
 

frontend/src/lib/api/account.ts

@@ -1,4 +1,5 @@
 import { apiClient } from './client';
+import { getClientTimeZone } from '@/lib/i18n/clientTimeZone';
 
 export type WorkingHoursPayload = {
   autoRepeatWeekly: boolean;
@@ -42,7 +43,10 @@ export const accountApi = {
   upsertMyWorkingHours: async (
     payload: WorkingHoursPayload,
   ): Promise<{ success: boolean; message: string }> => {
-    const response = await apiClient.put('/auth/profile/working-hours', payload);
+    const response = await apiClient.put('/auth/profile/working-hours', {
+      ...payload,
+      timeZone: getClientTimeZone(),
+    });
     return response.data;
   },
 };

frontend/src/lib/api/appointments.ts

@@ -1,5 +1,6 @@
 import { apiClient } from './client';
 import type { AppointmentColumnProvider, AppointmentRecord } from '@/types/appointment';
+import { getClientTimeZone } from '@/lib/i18n/clientTimeZone';
 import { toDateInputValue } from '@/components/appointments/appointmentTime';
 
 export interface CreateAppointmentBody {
@@ -27,7 +28,10 @@ export const appointmentsApi = {
   },
 
   create: async (body: CreateAppointmentBody): Promise<{ success: boolean; data: AppointmentRecord }> => {
-    const response = await apiClient.post('/appointments', body);
+    const response = await apiClient.post('/appointments', {
+      ...body,
+      timeZone: getClientTimeZone(),
+    });
     return response.data;
   },
 
@@ -35,7 +39,10 @@ export const appointmentsApi = {
     id: string,
     body: UpdateAppointmentBody,
   ): Promise<{ success: boolean; data: AppointmentRecord }> => {
-    const response = await apiClient.patch(`/appointments/${id}`, body);
+    const response = await apiClient.patch(`/appointments/${id}`, {
+      ...body,
+      timeZone: getClientTimeZone(),
+    });
     return response.data;
   },
 

frontend/src/lib/api/staff.ts

@@ -1,4 +1,5 @@
 import { apiClient } from './client';
+import { getClientTimeZone } from '@/lib/i18n/clientTimeZone';
 
 export interface StaffMemberDto {
   id: string;
@@ -142,7 +143,10 @@ export const staffApi = {
       blocks: { dayOfWeek: number; startMinute: number; endMinute: number; sortOrder?: number }[];
     },
   ): Promise<{ success: boolean; message: string }> => {
-    const response = await apiClient.put(`/staff/members/${membershipId}/working-hours`, body);
+    const response = await apiClient.put(`/staff/members/${membershipId}/working-hours`, {
+      ...body,
+      timeZone: getClientTimeZone(),
+    });
     return response.data;
   },
 };

frontend/src/lib/i18n/clientTimeZone.ts

@@ -0,0 +1,8 @@
+/** Browser IANA zone (e.g. Asia/Tehran). Used so the UTC server can interpret wall-clock hours. */
+export function getClientTimeZone(): string {
+  try {
+    return Intl.DateTimeFormat().resolvedOptions().timeZone || 'UTC';
+  } catch {
+    return 'UTC';
+  }
+}