fix: use local time with 3am cutover for today's date

new Date().toISOString() returns UTC, causing the calendar to advance
to the next day at 8pm EDT / 7pm EST. getTodayLocal() reads local
wall-clock time and rolls back one day before 3am so the calendar
stays on the current day through the night.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/page.tsx

@@ -5,6 +5,7 @@ import { Legend } from "@/components/Legend";
 import { EmptyState } from "@/components/EmptyState";
 import { PARKS, groupByRegion } from "@/lib/parks";
 import { openDb, getDateRange } from "@/lib/db";
+import { getTodayLocal } from "@/lib/env";
 
 interface PageProps {
   searchParams: Promise<{ week?: string }>;
@@ -18,9 +19,10 @@ function getWeekStart(param: string | undefined): string {
       return d.toISOString().slice(0, 10);
     }
   }
-  const today = new Date();
-  today.setDate(today.getDate() - today.getDay());
-  return today.toISOString().slice(0, 10);
+  const todayIso = getTodayLocal();
+  const d = new Date(todayIso + "T00:00:00");
+  d.setDate(d.getDate() - d.getDay());
+  return d.toISOString().slice(0, 10);
 }
 
 function getWeekDates(sundayIso: string): string[] {
@@ -32,9 +34,10 @@ function getWeekDates(sundayIso: string): string[] {
 }
 
 function getCurrentWeekStart(): string {
-  const today = new Date();
-  today.setDate(today.getDate() - today.getDay());
-  return today.toISOString().slice(0, 10);
+  const todayIso = getTodayLocal();
+  const d = new Date(todayIso + "T00:00:00");
+  d.setDate(d.getDate() - d.getDay());
+  return d.toISOString().slice(0, 10);
 }
 
 export default async function HomePage({ searchParams }: PageProps) {
@@ -42,7 +45,7 @@ export default async function HomePage({ searchParams }: PageProps) {
   const weekStart = getWeekStart(params.week);
   const weekDates = getWeekDates(weekStart);
   const endDate = weekDates[6];
-  const today = new Date().toISOString().slice(0, 10);
+  const today = getTodayLocal();
   const isCurrentWeek = weekStart === getCurrentWeekStart();
 
   const db = openDb();

app/park/[id]/page.tsx

@@ -10,6 +10,7 @@ import { ParkMonthCalendar } from "@/components/ParkMonthCalendar";
 import { LiveRidePanel } from "@/components/LiveRidePanel";
 import type { RideStatus, RidesFetchResult } from "@/lib/scrapers/sixflags";
 import type { LiveRidesResult } from "@/lib/scrapers/queuetimes"; // used as prop type below
+import { getTodayLocal } from "@/lib/env";
 
 interface PageProps {
   params: Promise<{ id: string }>;
@@ -23,8 +24,8 @@ function parseMonthParam(param: string | undefined): { year: number; month: numb
       return { year: y, month: m };
     }
   }
-  const now = new Date();
-  return { year: now.getFullYear(), month: now.getMonth() + 1 };
+  const [y, m] = getTodayLocal().split("-").map(Number);
+  return { year: y, month: m };
 }
 
 export default async function ParkPage({ params, searchParams }: PageProps) {
@@ -34,7 +35,7 @@ export default async function ParkPage({ params, searchParams }: PageProps) {
   const park = PARK_MAP.get(id);
   if (!park) notFound();
 
-  const today = new Date().toISOString().slice(0, 10);
+  const today = getTodayLocal();
   const { year, month } = parseMonthParam(monthParam);
 
   const db = openDb();

components/WeekCalendar.tsx

@@ -3,6 +3,7 @@ import Link from "next/link";
 import type { Park } from "@/lib/scrapers/types";
 import type { DayData } from "@/lib/db";
 import type { Region } from "@/lib/parks";
+import { getTodayLocal } from "@/lib/env";
 
 interface WeekCalendarProps {
   parks: Park[];
@@ -222,7 +223,7 @@ function ParkRow({
 }
 
 export function WeekCalendar({ parks, weekDates, data, grouped }: WeekCalendarProps) {
-  const today = new Date().toISOString().slice(0, 10);
+  const today = getTodayLocal();
   const parsedDates = weekDates.map(parseDate);
 
   const firstMonth = parsedDates[0].month;

lib/env.ts

@@ -11,3 +11,25 @@ export function parseStalenessHours(envVar: string | undefined, defaultHours: nu
   const parsed = parseInt(envVar ?? "", 10);
   return Number.isFinite(parsed) && parsed > 0 ? parsed : defaultHours;
 }
+
+/**
+ * Returns today's date as YYYY-MM-DD using local wall-clock time with a 3 AM
+ * switchover. Before 3 AM local time we still consider it "yesterday", so the
+ * calendar doesn't flip to the next day at midnight while people are still out
+ * at the park.
+ *
+ * Important: `new Date().toISOString()` returns UTC, which causes the date to
+ * advance at 8 PM EDT (UTC-4) or 7 PM EST (UTC-5) — too early. This helper
+ * corrects that by using local year/month/day components and rolling back one
+ * day when the local hour is before 3.
+ */
+export function getTodayLocal(): string {
+  const now = new Date();
+  if (now.getHours() < 3) {
+    now.setDate(now.getDate() - 1);
+  }
+  const y = now.getFullYear();
+  const m = String(now.getMonth() + 1).padStart(2, "0");
+  const d = String(now.getDate()).padStart(2, "0");
+  return `${y}-${m}-${d}`;
+}