add crontab site

.github/workflows/lighthouse.yml

@@ -24,6 +24,9 @@ jobs:
       - name: Validate SEO metadata and canonical URLs
         run: python3 scripts/seo-audit.py
 
+      - name: Test cron parsing and schedule evaluation
+        run: node --test scripts/crontab.test.cjs
+
       - name: Validate HTML
         uses: Cyb3r-Jak3/html5validator-action@v7.2.0
         with:
@@ -48,6 +51,7 @@ jobs:
             kubernetes-rbac-explorer/index.html
             visual-subnet-calculator/index.html
             yaml-formatter/index.html
+            crontab/index.html
             terraform-modules/index.html
           fail: true
           jobSummary: true
@@ -72,4 +76,5 @@ jobs:
             http://127.0.0.1:8080/kubernetes-rbac-explorer/
             http://127.0.0.1:8080/visual-subnet-calculator/
             http://127.0.0.1:8080/yaml-formatter/
+            http://127.0.0.1:8080/crontab/
             http://127.0.0.1:8080/terraform-modules/

README.md

@@ -108,6 +108,45 @@ operations, sensitive cluster access, RBAC administration, aggregated
 ClusterRoles, and incomplete policy exports. Consecutive sample selections do
 not repeat the same scenario.
 
+## Cron Schedule Builder
+
+Open `/crontab/` to build and explain cron expressions, preview
+upcoming times in an IANA time zone alongside UTC, and export scheduler configuration.
+Linux cron, Kubernetes CronJob, GitHub Actions, and AWS EventBridge Scheduler
+have separate validation rules and configuration exports. Presets and field
+shortcuts help build expressions without memorizing syntax.
+The time-zone field accepts manual IANA names and provides a searchable dropdown
+with mouse, touch, and keyboard selection.
+Choose 1, 2, 5, 10, 25, or 50 upcoming runs; share links retain the selected count.
+
+The builder supports lists, ranges, steps, named months and weekdays, common
+Linux/Kubernetes macros, Kubernetes question-mark wildcards, and AWS year,
+last-day, nearest-weekday, last-weekday, and nth-weekday fields. It handles
+missing and repeated local times, including half-hour clock changes, according
+to the documented preview policy for each platform. GitHub's undocumented
+fall-back behavior is explicitly modeled as the first occurrence. Actual
+execution remains the scheduler's responsibility.
+
+The preview searches eight calendar years after a user-selected UTC instant.
+Rare or impossible schedules report partial or empty results separately from
+syntax errors. Configuration, CSV downloads, and share links are generated in
+the browser. Sharing encodes settings in the URL fragment; there is no backend.
+Quartz, seconds fields, rate expressions, and `@reboot` are not supported.
+
+The dependency-free engine is in `crontab/cron.js`; DOM interaction
+and exports are in `app.js`, with page markup and responsive styles alongside them.
+Run the calendar and timezone regression tests with Node.js 22 or later:
+
+```sh
+node --test scripts/crontab.test.cjs
+```
+
+The page includes static instructions, crontab examples, a syntax reference,
+visible breadcrumbs, and connected page/application/author/image structured data.
+`python3 scripts/seo-audit.py` verifies these SEO relationships and related-tool
+links. Follow the crontab checks in [`SEARCH_CONSOLE.md`](./SEARCH_CONSOLE.md)
+after deployment to inspect indexing and measure actual search performance.
+
 ## Terraform Modules
 
 Open `/terraform-modules/` to explore public AWS Terraform modules
@@ -187,6 +226,7 @@ python3 -m http.server 8080
 - `http://localhost:8080/kubernetes-rbac-explorer/`
 - `http://localhost:8080/visual-subnet-calculator/`
 - `http://localhost:8080/yaml-formatter/`
+- `http://localhost:8080/crontab/`
 - `http://localhost:8080/terraform-modules/`
 
 ## Quality and search checks

SEARCH_CONSOLE.md

@@ -6,6 +6,8 @@ directives, matching Open Graph and structured-data URLs, and an entry in
 `sitemap.xml`. `robots.txt` advertises that sitemap. The duplicate
 `/json-formatter/` alias points directly to `/yaml-formatter/` through an instant
 meta refresh and a canonical link; it is excluded from the sitemap and navigation.
+The cron tool is published only at `/crontab/`, with the same canonical URL in
+its page metadata, structured data, navigation, and sitemap.
 
 Ownership verification must be completed by a Google account with access to
 Search Console. The verification value is account-issued and must not be
@@ -35,8 +37,9 @@ invented or replaced with a placeholder.
    - `https://native-cube.com/kubernetes-rbac-explorer/`
    - `https://native-cube.com/visual-subnet-calculator/`
    - `https://native-cube.com/yaml-formatter/`
+   - `https://native-cube.com/crontab/`
    - `https://native-cube.com/terraform-modules/`
-4. Do not submit `/json-formatter/`; it is a permanent redirect alias.
+4. Do not submit `/json-formatter/`; it is a redirect alias.
 
 ## Confirm Google's selected canonical
 
@@ -76,8 +79,8 @@ python3 scripts/check-redirects.py
 ```
 
 It checks every sitemap page across HTTP/HTTPS, apex/`www`, and the old GitHub
-Pages hostname, plus slashless paths, `index.html` duplicates, and formatter
-aliases. It follows HTTP and instant meta-refresh redirects explicitly, rejects
+Pages hostname, plus slashless paths, `index.html` duplicates, and the formatter
+alias. It follows HTTP and instant meta-refresh redirects explicitly, rejects
 loops and temporary or insecure redirects, and checks that each final page is
 HTTP 200 with the expected canonical and no indexing restrictions. The separate
 **Live redirect checks** workflow runs weekly and can be started manually in
@@ -98,7 +101,7 @@ permanently to the apex HTTPS URLs. The formatter alias still served the old
 `noindex` directive before this change was deployed. This is a consolidation
 signal issue; it does not prove the cause of an account's **Redirect error**.
 
-## Hosting settings and the formatter alias
+## Hosting settings and redirect aliases
 
 Keep **Settings → Pages → Custom domain** set to `native-cube.com` and
 **Enforce HTTPS** enabled. The repository's `CNAME` file does not by itself
@@ -128,6 +131,48 @@ After publishing, rerun the live audit, resubmit the canonical sitemap, and use
 pages and validate actual **Redirect error** fixes. Historical exclusions remain
 until Google recrawls them, and intentional redirects remain excluded.
 
+## Check and measure the crontab page
+
+After publishing changes to `/crontab/`:
+
+1. Inspect `https://native-cube.com/crontab/` with **Test live URL**. Confirm HTTP
+   200, an indexable response, and the exact same user-declared canonical. The
+   slashless URL, `/index.html` variant, query strings, and share fragments must
+   not become separate sitemap entries.
+2. Review the rendered HTML and screenshot. The crontab heading, quick-start
+   instructions, syntax guide, examples, scheduler notes, FAQ, and ordinary
+   navigation links are in the original HTML. Only interactive calculations
+   require JavaScript. Keep the tool's default preview at two runs.
+3. Validate the JSON-LD with the
+   [Schema Markup Validator](https://validator.schema.org/) and Google's
+   [Rich Results Test](https://search.google.com/test/rich-results). `WebPage`,
+   `WebApplication`, `BreadcrumbList`, `Person`, and `ImageObject` describe the
+   actual content and free access. Google's
+   [software app rich-result requirements](https://developers.google.com/search/docs/appearance/structured-data/software-app)
+   include a genuine rating or review; the tool does not currently publish
+   either. Do not invent one to remove an eligibility warning. The visible FAQ
+   does not imply eligibility for FAQ rich results, which Google
+   [limits to qualifying government and health sites](https://developers.google.com/search/blog/2023/08/howto-faq-changes).
+4. Request indexing for the canonical URL after the live checks pass, and
+   confirm that Google's selected canonical eventually matches it. Account
+   ownership and URL inspection are performed in Search Console; a passing
+   local audit cannot establish that a page is indexed.
+5. In **Performance → Search results**, filter **Page** to the exact canonical
+   URL. Compare impressions, clicks, CTR, and average position over comparable
+   date ranges, then segment by device, country, and query. Initial query groups
+   to inspect include crontab generators, cron expression testers, common
+   schedules, and time-zone questions. These are hypotheses, not measured
+   keyword volumes or ranking predictions.
+6. Check the **Core Web Vitals** report when field data is available. Local
+   Lighthouse scores measure a lab run, not real-user performance or ranking.
+
+The SEO audit verifies the crontab schema relationships, matching page and social
+titles, static examples, incoming links from related tools, and agreement between
+`dateModified` and sitemap `lastmod`. It runs in the existing Lighthouse and SEO
+workflow. Shared schedules remain URL fragments and retain the same clean
+canonical, following Google's
+[canonicalization guidance](https://developers.google.com/search/docs/crawling-indexing/consolidate-duplicate-urls).
+
 ## Keep sitemap dates accurate
 
 Update a page's `lastmod` when its public content or metadata changes. The