chore(website): Update NUSMods for AY2026/2027

[jloh02]

Summary

• switch the website config to AY2026/2027 while keeping the current semester unchanged for the Special Term overlap window
• keep examAvailability unchanged because it is keyed by semester number, and previous AY Special Term exam data should remain visible during overlap
• add AY2026/2027 semester start dates to the academic calendar package so previous-AY Special Term I/II auto-routing ends when new AY Semester 1 starts
• update the new-course-data announcement for AY2026/2027

Special Term rollover

specialTermAcademicYear remains null. The existing calendar-based overlap logic continues to source Semesters 3 and 4 from AY2025/2026 until AY2026/2027 Semester 1 starts on 10 Aug 2026. The separate PR3 step in MAINTENANCE.md should handle setting semester to 1 and adding AY2025/2026 to archiveYears closer to that date.

Data sources

• NUS Registrar academic calendar: https://www.nus.edu.sg/registrar/calendar
• NUS CourseReg schedule: https://www.nus.edu.sg/coursereg/schedule-and-timeline.html
• Singapore public holidays (MOM, updated 19 Jun 2026): https://www.mom.gov.sg/employment-practices/public-holidays

Verification

• pnpm --filter nusmods typecheck
• pnpm --filter nusmods test src/config/config.test.ts src/utils/specialTerm.test.ts src/views/components/module-info/ModuleWorkload.test.tsx src/actions/moduleBank.test.ts

Note: pnpm reported the repo's Node 22 engine warning because this local shell is running Node 24.14.0.

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2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
nusmods-export	Ignored	Preview	Jun 27, 2026 4:19am
nusmods-website	Ignored	Preview	Jun 27, 2026 4:19am

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.31%. Comparing base (988c6fd) to head (a3fe698).
⚠️ Report is 245 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4433      +/-   ##
==========================================
+ Coverage   54.52%   57.31%   +2.78%     
==========================================
  Files         274      317      +43     
  Lines        6076     7173    +1097     
  Branches     1455     1748     +293     
==========================================
+ Hits         3313     4111     +798     
- Misses       2763     3062     +299     

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[greptile-apps]

Greptile Summary

This PR rolls the website configuration forward for AY2026/2027. The main changes are:

• Updates the website academic year while keeping the current semester setting.
• Adds AY2026/2027 semester start dates to the academic calendar package.
• Refreshes ModReg schedule dates for several registration rounds.
• Updates the new-course-data announcement copy and key.
• Adjusts maintenance checklist notes for the AY rollover process.

Confidence Score: 3/5

Merge should wait for the CourseReg schedule data to be corrected so CPEx and notification behavior match the AY2026/2027 rollout.

The changes are narrow configuration/data updates with targeted test coverage reported, but one stale CPEx date path was reproduced to hide the relevant window and suppress reminders.

website/src/data/modreg-schedule.json

T-Rex Logs

What T-Rex did

• Ran a targeted Node harness against the CPEx schedule with the clock fixed to 2026-07-20T10:00:00+08:00 to verify CPEx dates remained stale.
• Created two artifacts documenting the CPEx stale-date reproduction.
• Inspected the calendar data baseline and the post-change state to observe AY2026/2027 data and initial routing behavior around the new calendar start.
• Observed that, after the 2026-08-10T00:00:00+08:00 mark, previousActive remained true and routing did not stop until 2026-08-11T00:00:00+08:00, indicating lingering state beyond the initial date.

_{Ran code and verified through T-Rex}

Comments Outside Diff (2)

1. website/src/data/modreg-schedule.json, line 40-43 (link)

   CPEx dates stayed stale

   The CourseReg rounds were moved to the AY2026/2027 Semester 1 window, but the CPEx entry still ends on 13 Mar 2026. /cpex reads this entry through config.modRegSchedule while the page constants already say AY2026/2027 Semester 1, so any visit after March renders “CPEx has ended for AY2026/2027 Semester 1” and hides the upcoming/current CPEx window. The ModReg notification selector also drops ended rounds, so CPEx reminders will not appear for the new exercise until these dates are updated.

   Artifacts

   
   

   Repro: targeted CPEx stale date harness

   • Contains supporting evidence from the run (text/javascript; charset=utf-8).

   Repro: harness output showing stale CPEx is ended and omitted from notifications

   • Keeps the command output available without making the summary code-heavy.

   

   _{Ran code and verified through T-Rex}

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: website/src/data/modreg-schedule.json
   Line: 40-43
   
   Comment:
   **CPEx dates stayed stale**
   
   The CourseReg rounds were moved to the AY2026/2027 Semester 1 window, but the CPEx entry still ends on 13 Mar 2026. `/cpex` reads this entry through `config.modRegSchedule` while the page constants already say AY2026/2027 Semester 1, so any visit after March renders “CPEx has ended for AY2026/2027 Semester 1” and hides the upcoming/current CPEx window. The ModReg notification selector also drops ended rounds, so CPEx reminders will not appear for the new exercise until these dates are updated.
   
   How can I resolve this? If you propose a fix, please make it concise.

2. General comment

   Previous-AY special-term routing remains active on the AY2026/2027 Semester 1 start date

   • Bug
     • The PR contract requires previous-AY Special Term I/II auto-routing to end when AY2026/2027 Semester 1 starts on 10 Aug 2026. Runtime validation of head shows calendar-2026/2027-sem1-start: [2026,8,10], but for 2026-08-10T00:00:00+08:00 the code still returns previousActive:true, effectiveSpecialTermAcademicYear:"2025/2026", and routes Semesters 3 and 4 to the previous AY. It does not stop previous-AY routing until 2026-08-11T00:00:00+08:00.
   • Cause
     • The calendar stores semester starts as local dates via new Date(year, month - 1, day), which is midnight in the runtime timezone. The validation scenario uses Singapore-time timestamps (+08:00), so 2026-08-10T00:00:00+08:00 is still before new Date(2026, 7, 10) in a UTC runtime. The changed AY2026/2027 calendar line packages/nusmods-academic-calendar/academic-calendar.json:65 supplies [2026, 8, 10], but the date comparison boundary is timezone-sensitive and therefore misses the Singapore start-of-day contract.
   • Fix
     • Make academic-calendar date comparisons timezone-stable for the NUS/Singapore academic calendar, for example by normalizing comparisons to Singapore local dates or by constructing semester boundary instants explicitly at Asia/Singapore start-of-day. Then add a regression test asserting isUsingPreviousAySpecialTermData('2026/2027', null, new Date('2026-08-10T00:00:00+08:00')) === false and Semesters 3/4 no longer use the previous AY at that instant.

   _{Ran code and verified through T-Rex}

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
website/src/data/modreg-schedule.json:40-43
**CPEx dates stayed stale**

The CourseReg rounds were moved to the AY2026/2027 Semester 1 window, but the CPEx entry still ends on 13 Mar 2026. `/cpex` reads this entry through `config.modRegSchedule` while the page constants already say AY2026/2027 Semester 1, so any visit after March renders “CPEx has ended for AY2026/2027 Semester 1” and hides the upcoming/current CPEx window. The ModReg notification selector also drops ended rounds, so CPEx reminders will not appear for the new exercise until these dates are updated.

### Issue 2 of 2
website/src/data/modreg-schedule.json:6-19
**Round dates mismatch**

Please re-check these Select Courses dates against the official AY2026/27 Semester 1 CourseReg schedule. The NUS schedule excerpt for undergraduate/CPE students lists Select Courses Round 1 on 26-Jul-26, but this data starts Round 1 on 20-Jul-26. Since ModReg notifications and the report-error visibility window are driven directly from this JSON, a shifted Round 1 date can notify students and open the enhanced reporting window almost a week early.

_{Reviews (5): Last reviewed commit: "chore: update PR2 instructions" | Re-trigger Greptile}

[leslieyip02]

Correct me if I'm wrong, but this doesn't seem needed anymore. We haven't been doing it for the past few years anyways.

[leslieyip02]

Greptile Summary

Switching academicYear to 2026/2027 makes AY2025/2026 the immediate previous year, but archiveYears still stops at AY2024/2025. fetchAllModuleArchive(), isArchiveLoading(), and availableArchive() only iterate this list, so a course that is no longer offered in AY2026/2027 but existed in AY2025/2026 will show the plain 404 page instead of the AY2025/2026 archive link.

The remaining comment on archiveYears will be fixed in PR3.

[leslieyip02]

@jloh02 Can you take another look? I added the CourseReg dates so it should be good to go now.