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4 back-office tools: payroll register reconciliation, employee census checker, SaaS spend finder, contract renewal tracker. Local CSV. $49 ($86 separately).
View Back-Office Ops Skills BundleCron Expression Explainer & Checker (Free)
Know exactly when a cron job will run before it surprises you.
What it does
Paste a cron expression and get it in plain English, the next run times in your time zone, and warnings for the mistakes that make jobs run at the wrong time. Works for crontab, GitHub Actions, Kubernetes CronJob, Spring and Quartz. It can also scan crontab files, workflow files and CronJob YAML in one go. Python standard library only.
$ python3 -m cronx "0 9 1-7 * 1" --tz America/New_York
0 9 1-7 * 1 (standard cron)
at 09:00, on day 1 through 7 of the month OR on Monday (cron runs when either matches)
next runs (America/New_York): 2026-11-09 09:00, 2026-11-16 09:00, ...
WARN DOM_DOW_OR: both day-of-month and day-of-week are set: standard cron runs when EITHER matches ...What you get
The screenshot is real output from the kit’s own commands. Tested from a fresh download of this exact zip: ./run_tests.sh ran 7 tests OK on Python 3.13 and 3.10.
What it understands
- Standard cron (Vixie/cronie, GitHub Actions, Kubernetes): 5 fields, ranges, lists, steps, JAN-DEC and SUN-SAT names, wrap-around ranges like fri-mon, 0/7 for Sunday, and @daily, @weekly and the other macros. When both day fields are set, cron's OR rule applies.
- Spring (6 fields, seconds first): ?, L, L-3, LW, 15W, 5L, 5#3, and 0/7 = Sunday.
- Quartz (6 or 7 fields with year, --quartz): ? required in one day field, 1 = Sunday, L, W and #.
- Time zones: next runs in any IANA zone (--tz Europe/Berlin). Times skipped by a daylight-saving jump are shown at the real instant.
Warnings
| Check | Mistake |
|---|---|
| DOM_DOW_OR | 0 9 1-7 * 1 is not "first Monday": it runs every Monday and on days 1-7 |
| UNEVEN_STEP | */7 minutes resets each hour (:56 then :00) |
| EVERY_MINUTE_IN_HOUR | * 3 * * * runs 60 times between 03:00 and 03:59 |
| SKIPPED_MONTHS | day 31 (or 30, 29) never fires in shorter months |
| GITHUB_MIN_INTERVAL / GITHUB_NOTES | GitHub runs schedules at most every 5 minutes, in UTC unless timezone: is set, only on the default branch; busy at the top of the hour |
| K8S_TIMEZONE | CronJob uses the controller's zone unless spec.timeZone is set |
| WEEKDAY_NUMBERS | Spring and Quartz number weekdays differently |
| DST | 01:00-03:00 local jobs can be skipped or doubled on daylight-saving changes |
Scan files
python3 -m cronx scan crontab.txt .github/workflows/nightly.yml cronjob.yaml finds every schedule. That includes crontab lines (with CRON_TZ=), GitHub - cron: entries (with their timezone:) and CronJob schedule: lines. Each is explained and checked. Exit code 1 if any expression is invalid, so it can run in CI. --json for scripts.
./demo.sh runs both modes on the examples. ./run_tests.sh runs the tests. It's also a Claude Code plugin with a skill in skills/cron/.
Running infrastructure with Claude Code? DevOps & SRE Subagents adds 10 subagents for incidents, Terraform, Kubernetes, CI and alerts. It also includes a guard hook that asks before terraform apply or kubectl delete: https://youraitools.co/marketplace/devops-sre-subagents
Honest limits
- It explains and checks schedules; it doesn't run jobs.
- @reboot runs once at startup, so it has no schedule to explain and is rejected.
Format and license
Zip, 14 KB, v1.0, 14 files. Free to use, modify and share for any purpose, including commercial work, as long as this notice stays in copies. Not affiliated with or endorsed by GitHub or the Kubernetes project.
FAQ
- Is it free?
- Yes, enter your email for the newsletter or download directly.
- Does it support Quartz and Spring?
- Yes, including ?, L, W and #.
- Which time zone does GitHub Actions use?
- UTC unless the schedule sets timezone:. The tool shows the next runs in the right zone.
- How do I get the files?
- Click Download free. The zip downloads straight away: no checkout, no account.
- Do I have to sign up for the newsletter?
- No. The form is optional and the download works without it.
Get Cron Expression Explainer & Checker (Free)
Free cron expression explainer: plain English, next run times in your time zone, and warnings for common mistakes. Crontab, GitHub Actions, Kubernetes.
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