fix: use explicit Eastern timezone for day boundary instead of system TZ

getTodayLocal() relied on system clock hours, which broke in the web
container (TZ defaulting to UTC) — the day flipped at 11 PM EDT (3 AM
UTC) instead of 3 AM Eastern. Now uses Intl.DateTimeFormat with an
explicit America/New_York timezone. Also replaced all toISOString()
date formatting with local-component helpers to avoid UTC conversion.

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

backend/src/db/queries.ts

@@ -1,5 +1,6 @@
 import type Database from "better-sqlite3";
 import { getDb } from "./index";
+import { getTodayLocal } from "../../../lib/env";
 
 import type { DayData } from "../../../lib/types";
 export type { DayData };
@@ -126,7 +127,7 @@ export function isMonthScraped(
 ): boolean {
   const daysInMonth = new Date(year, month, 0).getDate();
   const lastDay = `${year}-${String(month).padStart(2, "0")}-${String(daysInMonth).padStart(2, "0")}`;
-  const today = new Date().toISOString().slice(0, 10);
+  const today = getTodayLocal();
 
   if (lastDay < today) return true;
 

backend/src/routes/calendar.ts

@@ -2,7 +2,7 @@ import { Hono } from "hono";
 import { PARKS } from "../../../lib/parks";
 import { QUEUE_TIMES_IDS } from "../../../lib/queue-times-map";
 import { getCoasterSet } from "../../../lib/coaster-data";
-import { getTodayLocal, isWithinOperatingWindow, getOperatingStatus } from "../../../lib/env";
+import { getTodayLocal, formatDateLocal, isWithinOperatingWindow, getOperatingStatus } from "../../../lib/env";
 import { fetchToday } from "../../../lib/scrapers/sixflags";
 import { fetchLiveRides } from "../../../lib/scrapers/queuetimes";
 import { getDateRange, getParkMonthData, type DayData } from "../db/queries";
@@ -22,7 +22,7 @@ app.get("/week", async (c) => {
   const weekDates = Array.from({ length: 7 }, (_, i) => {
     const d = new Date(startParam + "T00:00:00");
     d.setDate(d.getDate() + i);
-    return d.toISOString().slice(0, 10);
+    return formatDateLocal(d);
   });
   const endDate = weekDates[6];
   const today = getTodayLocal();
@@ -53,7 +53,7 @@ app.get("/week", async (c) => {
   const currentWeekStart = (() => {
     const d = new Date(today + "T00:00:00");
     d.setDate(d.getDate() - d.getDay());
-    return d.toISOString().slice(0, 10);
+    return formatDateLocal(d);
   })();
   const isCurrentWeek = startParam === currentWeekStart;