chore(scraper): Prepare scraper for AY2026/2027

[jloh02]

Summary

• update the NUS v2 scraper academic year to AY2026/2027
• add AY2026/2027 semester start dates to the academic calendar package so scraper Special Term I/II auto-routing can still source AY2025/2026 data during the overlap window
• add AY2026/2027 timetable holiday exclusions from the NUS Registrar calendar and MOM public holiday data
• include both actual Sunday holiday dates and observed Monday dates for applicable spillovers, so exact-date consumers such as Today and iCal exclusions handle both dates
• update MAINTENANCE.md so future annual prep keeps the academic calendar update in PR1 and leaves semester/archive rollover for PR3

Special Term rollover

specialTermAcademicYear remains null. With the AY2026/2027 calendar present, the scraper can auto-detect that previous AY Special Term I/II remains active until AY2026/2027 Semester 1 starts on 10 Aug 2026.

Data sources

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

Verification

• JSON parse, sorted-order, and duplicate check for website/src/data/holidays.json
• pnpm --filter nusmods-academic-calendar test
• pnpm --filter nus-v2 typecheck
• TZ=Asia/Singapore pnpm --filter nusmods test src/utils/ical.test.ts src/config/config.test.ts

Note: pnpm reported the repo's Node 22 engine warning because this local shell is running Node 24.14.0. Running the iCal test without TZ=Asia/Singapore in this thread's Europe/London timezone hits existing DST-sensitive expectations around 2016 dates.

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2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
nusmods-export	Ignored	Preview	Jun 27, 2026 3:19am
nusmods-website	Ignored	Preview	Jun 27, 2026 3:19am

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.31%. Comparing base (988c6fd) to head (7bdf4c6).
⚠️ Report is 245 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4432      +/-   ##
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+ 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 prepares the scraper and calendar data for AY2026/2027. The main changes are:

• Adds AY2026/2027 semester and Special Term start dates to the academic calendar package.
• Updates the NUS v2 scraper academic year to 2026/2027.
• Extends website holiday data with AY2026/2027 NUS and Singapore public holidays.
• Updates maintenance notes for the annual AY rollover flow.

Confidence Score: 5/5

The changes are merge-safe based on the scoped calendar, scraper configuration, holiday data, and maintenance documentation updates.

No correctness, security, or reliability issues were identified in the reviewed changes, and the provided validation covers JSON integrity, package tests, typechecking, and timezone-sensitive iCal behavior.

T-Rex Logs

What T-Rex did

• Ran the special-term-routing test using trex-artifacts/special-term-routing-script.js to generate before and after logs.
• Reviewed the after-run log trex-artifacts/special-term-routing-02-after.log and confirmed academicYear advanced to 2026/2027, calendarHas2026_2027 is true, and the routing behavior changed as described.
• Ran the holiday exclusions test and captured before and after logs for comparison.
• Reviewed trex-artifacts/holiday-exclusions-02-after.log and confirmed head holidays increased to 95, with all six target dates present in both raw data and iCal consumption.

_{Ran code and verified through T-Rex}

_{Reviews (6): Last reviewed commit: "Merge branch 'master' into codex/ay26-27..." | Re-trigger Greptile}

[jloh02]

Fixed the holiday spillover issue. The AY2026/2027 holiday block now includes both the actual Sunday dates and observed Monday dates for the MOM-published Sunday spillovers: National Day 2026, Deepavali 2026, and Chinese New Year day 2 in 2027.

[leslieyip02]

LGTM!