From e1902188409388c7997937f5a6ff33a9862ca614 Mon Sep 17 00:00:00 2001
From: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>
Date: Wed, 1 Oct 2025 21:17:27 +0200
Subject: [PATCH] fix(api): adjust daily-challenge time from UTC (#62444)

---
 .../routes/daily-coding-challenge.test.ts     | 63 ++++++++++++-------
 .../daily-coding-challenge/utils/helpers.ts   |  5 +-
 2 files changed, 43 insertions(+), 25 deletions(-)

diff --git a/api/src/daily-coding-challenge/routes/daily-coding-challenge.test.ts b/api/src/daily-coding-challenge/routes/daily-coding-challenge.test.ts
index 2fe0baec688..5d96df67845 100644
--- a/api/src/daily-coding-challenge/routes/daily-coding-challenge.test.ts
+++ b/api/src/daily-coding-challenge/routes/daily-coding-challenge.test.ts
@@ -1,26 +1,23 @@
-import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
 import { addDays } from 'date-fns';
 
 import { setupServer, superRequest } from '../../../vitest.utils.js';
-import { getNowUsCentral, getUtcMidnight } from '../utils/helpers.js';
 
 function dateToDateParam(date: Date): string {
   return date.toISOString().split('T')[0] as string;
 }
 
-const todayUsCentral = getNowUsCentral();
-const todayUtcMidnight = getUtcMidnight(todayUsCentral);
+const todayUsCentral = new Date(Date.UTC(2025, 9, 2, 5)); // 2025-10-02 00:00:00 in US Central
+const todayUtcMidnight = new Date(Date.UTC(2025, 9, 2, 0, 0, 0));
+
 const todayDateParam = dateToDateParam(todayUtcMidnight);
 
-const yesterdayUsCentral = addDays(todayUsCentral, -1);
-const yesterdayUtcMidnight = getUtcMidnight(yesterdayUsCentral);
+const yesterdayUtcMidnight = addDays(todayUtcMidnight, -1);
 
-const twoDaysAgoUsCentral = addDays(todayUsCentral, -2);
-const twoDaysAgoUtcMidnight = getUtcMidnight(twoDaysAgoUsCentral);
+const twoDaysAgoUtcMidnight = addDays(todayUtcMidnight, -2);
 const twoDaysAgoDateParam = dateToDateParam(twoDaysAgoUtcMidnight);
 
-const tomorrowUsCentral = addDays(todayUsCentral, 1);
-const tomorrowUtcMidnight = getUtcMidnight(tomorrowUsCentral);
+const tomorrowUtcMidnight = addDays(todayUtcMidnight, 1);
 const tomorrowDateParam = dateToDateParam(tomorrowUtcMidnight);
 
 const yesterdaysChallenge = {
@@ -79,6 +76,13 @@ const mockChallenges = [
 
 describe('/daily-coding-challenge', () => {
   setupServer();
+  // This has to happen after setupServer since it needs real timers.
+  beforeEach(() => {
+    vi.useFakeTimers({ now: todayUsCentral });
+  });
+  afterEach(() => {
+    vi.useRealTimers();
+  });
 
   describe('GET /daily-coding-challenge/date/:date', () => {
     beforeEach(async () => {
@@ -229,18 +233,10 @@ describe('/daily-coding-challenge', () => {
       }
     });
 
-    it('should return { id, date, challengeNumber, title } for all available challenges of the given month up to today US Central', async () => {
-      const currentMonth = todayUsCentral.toISOString().slice(0, 7);
-
-      const res = await superRequest(
-        `/daily-coding-challenge/month/${currentMonth}`,
-        {
-          method: 'GET'
-        }
-      ).send({});
-
-      expect(res.status).toBe(200);
-      expect(Array.isArray(res.body)).toBe(true);
+    it('should return two challenges on the second day of the month', async () => {
+      const res = await superRequest(`/daily-coding-challenge/month/2025-10`, {
+        method: 'GET'
+      }).send({});
 
       // Should include yesterday's and today's challenges, but not tomorrow's
       const expectedResponse = [
@@ -258,8 +254,29 @@ describe('/daily-coding-challenge', () => {
         }
       ];
 
-      expect(res.body).toHaveLength(2);
       expect(res.body).toEqual(expectedResponse);
+      expect(res.status).toBe(200);
+    });
+
+    it('should return one challenge on the first day of the month', async () => {
+      vi.setSystemTime(new Date(Date.UTC(2025, 9, 1, 5))); // 2025-10-01 00:00:00 in US Central
+
+      const res = await superRequest(`/daily-coding-challenge/month/2025-10`, {
+        method: 'GET'
+      }).send({});
+
+      // Should include yesterday's challenges
+      const expectedResponse = [
+        {
+          id: yesterdaysChallenge.id,
+          challengeNumber: yesterdaysChallenge.challengeNumber,
+          date: yesterdaysChallenge.date.toISOString(),
+          title: yesterdaysChallenge.title
+        }
+      ];
+
+      expect(res.body).toEqual(expectedResponse);
+      expect(res.status).toBe(200);
     });
 
     it('should return 404 when no challenges exist for the given month', async () => {
diff --git a/api/src/daily-coding-challenge/utils/helpers.ts b/api/src/daily-coding-challenge/utils/helpers.ts
index a5dccc65040..242d9fc4f73 100644
--- a/api/src/daily-coding-challenge/utils/helpers.ts
+++ b/api/src/daily-coding-challenge/utils/helpers.ts
@@ -1,10 +1,11 @@
-import { toZonedTime } from 'date-fns-tz';
+import { getTimezoneOffset } from 'date-fns-tz';
 
 /**
  * @returns Now US Central time.
  */
 export function getNowUsCentral() {
-  return toZonedTime(new Date(), 'America/Chicago');
+  const offset = getTimezoneOffset('America/Chicago', new Date());
+  return new Date(Date.now() + offset);
 }
 
 /**