Add timezone update workflow

.github/workflows/timezone-update.yml

@@ -0,0 +1,48 @@
+name: Timezone update
+on:
+  schedule:
+    # Run once a week at 00:05 AM UTC on Sunday.
+    - cron: 5 0 * * 0
+
+  workflow_dispatch:
+
+jobs:
+  timezone_update:
+    if: github.repository == 'nodejs/node'
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout nodejs/node
+        uses: actions/checkout@v3
+        with:
+          persist-credentials: false
+
+      - name: Checkout unicode-org/icu-data
+        uses: actions/checkout@v3
+        with:
+          path: icu-data
+          persist-credentials: false
+          repository: unicode-org/icu-data
+
+      - run: ./tools/update-timezone.mjs
+
+      - name: Open Pull Request
+        uses: gr2m/create-or-update-pull-request-action@6720400cad8e74d7adc64640e4e6ea6748b83d8f  # Create a PR or update the Action's existing PR
+        env:
+          GITHUB_TOKEN: ${{ secrets.GH_USER_TOKEN }}
+        with:
+          author: Node.js GitHub Bot <github-bot@iojs.org>
+          body: |
+            This PR was generated by tools/timezone-update.yml.
+
+            Updates the ICU files as per the instructions present in https://github.com/nodejs/node/blob/main/doc/contributing/maintaining-icu.md#time-zone-data
+
+            To test, build node off this branch & log the version of tz using
+            ```js
+            console.log(process.versions.tz)
+            ```
+          branch: actions/timezone-update
+          commit-message: 'deps: update timezone'
+          labels: dependencies
+          title: 'deps: update timezone'
+          reviewers: \@nodejs/i18n-api

tools/update-timezone.mjs

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+#!/usr/bin/env node
+// Usage: tools/update-timezone.mjs
+import { execSync, spawnSync } from 'node:child_process';
+import { renameSync, readdirSync, rmSync } from 'node:fs';
+import { exit } from 'node:process';
+
+const fileNames = [
+  'zoneinfo64.res',
+  'windowsZones.res',
+  'timezoneTypes.res',
+  'metaZones.res',
+];
+
+const availableVersions = readdirSync('icu-data/tzdata/icunew', { withFileTypes: true })
+.filter((dirent) => dirent.isDirectory())
+.map((dirent) => dirent.name);
+
+const currentVersion = process.versions.tz;
+const latestVersion = availableVersions.sort().at(-1);
+
+if (latestVersion === currentVersion) {
+  console.log(`Terminating early, tz version is latest @ ${currentVersion}`);
+  exit();
+}
+
+execSync('bzip2 -d deps/icu-small/source/data/in/icudt*.dat.bz2');
+fileNames.forEach((file) => {
+  renameSync(`icu-data/tzdata/icunew/${latestVersion}/44/le/${file}`, `deps/icu-small/source/data/in/${file}`);
+  spawnSync(
+    'icupkg', [
+      '-a',
+      file,
+      'icudt*.dat',
+    ], { cwd: 'deps/icu-small/source/data/in/' }
+  );
+  rmSync(`deps/icu-small/source/data/in/${file}`);
+});
+execSync('bzip2 -z deps/icu-small/source/data/in/icudt*.dat');
+rmSync('icu-data', { recursive: true });