deps: ICU tzdata needs update to 2026a for America/Vancouver (BC permanent DST)

Why this is a good first issue

The issue requires updating ICU tzdata to 2026a for correct DST handling in America/Vancouver.

AI Summary

The issue involves updating the ICU tzdata to version 2026a to correctly handle the permanent DST change in America/Vancouver. The fix is already documented and partially implemented via PR #62164. No major blockers are present, but backports to LTS lines will be needed.

Issue Description

Version

v25.8.1

Platform

Linux wp10 6.17.0-19-generic #19-Ubuntu SMP PREEMPT_DYNAMIC Fri Mar  6 14:02:58 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

British Columbia adopted permanent DST effective November 1, 2026. Node.js currently has America/Vancouver falling back to PST (UTC-8) that day, which will be incorrect. You can verify the bug after November 1, 2026:

node -e "console.log(process.versions.tz)"  // shows current tzdata version
node -e "console.log(new Intl.DateTimeFormat('en-CA', {
  timeZone: 'America/Vancouver',
  timeZoneName: 'short',
  year: 'numeric', month: '2-digit', day: '2-digit',
  hour: '2-digit', minute: '2-digit'
}).format(new Date('2026-11-01T09:00:00Z')))"
// Expected on patched Node:  2026-11-01, 02:00 PDT
// Actual on unpatched Node:  2026-11-01, 01:00 PST  ← wrong

Root cause: The bundled ICU tzdata predates IANA 2026a (released 2026-03-01), which includes the America/Vancouver rule change. Reference: https://github.com/eggert/tz/commit/8b46071fd85a7a9434d63894bac64d30362cc16d

Note also ICU 78.3 mentions updates to timezone data 2026a

Fix: Update deps/icu-small to include tzdata 2026a per the process documented in maintaining-icu.md.

Urgency: The detonation date is November 1, 2026, so there is time, but backports to LTS lines (v22.x, v24.x) will be needed.

How often does it reproduce? Is there a required condition?

Always reproducible, no required conditions

What is the expected behavior? Why is that the expected behavior?

$ node -e "console.log(process.versions.tz)"
2026a
$ node -e "console.log(new Intl.DateTimeFormat('en-CA', {
  timeZone: 'America/Vancouver',
  timeZoneName: 'short',
  year: 'numeric', month: '2-digit', day: '2-digit',
  hou

GitHub Labels

icu