apps/pwa/src/lib/eventDateTime.ts

@@ -68,8 +68,12 @@ function pad2(n: number): string {
   return n < 10 ? `0${n}` : `${n}`
 }
 
-/** Format a Date as 'YYYY-MM-DD' using LOCAL calendar accessors. */
-function localDateISO(d: Date): string {
+/**
+ * Format a Date as 'YYYY-MM-DD' using LOCAL calendar accessors.
+ * WR-04: exported as the single source for local-date formatting so calendarStore
+ * (initialCalendarRange/todayIso) can drop its banned toISOString().slice(0,10).
+ */
+export function localDateISO(d: Date): string {
   return `${d.getFullYear()}-${pad2(d.getMonth() + 1)}-${pad2(d.getDate())}`
 }
 

apps/pwa/src/store/calendarStore.ts

@@ -24,6 +24,7 @@
  */
 
 import { create } from 'zustand'
+import { localDateISO } from '../lib/eventDateTime.js'
 
 // ── Types ──────────────────────────────────────────────────────────────────
 
@@ -126,15 +127,19 @@ function initialCalendarRange(): { start: string; end: string } {
   start.setDate(start.getDate() - 7)
   const end = new Date(today.getFullYear(), today.getMonth() + 1, 0)
   end.setDate(end.getDate() + 7)
+  // WR-04: localDateISO uses local calendar accessors — NEVER toISOString().slice(0,10),
+  // which returns the UTC date and (for the project's negative-offset zones after ~20:00
+  // local) seeds the window/selectedDate on the wrong day.
   return {
-    start: start.toISOString().slice(0, 10),
-    end: end.toISOString().slice(0, 10),
+    start: localDateISO(start),
+    end: localDateISO(end),
   }
 }
 
 /** Today as an ISO date string (YYYY-MM-DD). Exported for use in EventForm (IN-03). */
 export function todayIso(): string {
-  return new Date().toISOString().slice(0, 10)
+  // WR-04: local-date accessor, not the banned UTC slice.
+  return localDateISO(new Date())
 }
 
 // ── Store ──────────────────────────────────────────────────────────────────