cron-doctor
Diagnose and validate cron expressions before they ship. Catches the five silent death-traps: impossible dates that never fire, OR-semantics that fire too often, midnight spikes, uneven step drift, and leap-year February 29.
Profile →npx skills add sickn33/agentic-awesome-skills --skill cron-doctor --agent claude-code
Same command for any agent — swap --agent for codex, cursor, copilot.
Weekly change comes from our own snapshots, not the repository page — it measures attention, not adoption.
# cron-doctor ## Overview Cron is deceptively error-prone. The failure mode is **silent** — a syntactically valid expression that simply never fires, or fires far more often than intended. `0 0 30 2 *` parses cleanly and then sits dead forever (February has no 30th). `0 0 1,15 * 1` looks like "1st and 15th if Monday" but actually means "1st, 15th, **OR** every Monday" — ~6 fires/month instead of ~2. This skill teaches an agent to catch those before they reach production. It comes with a zero-dependency validation engine (`scripts/cron-engine.js`, no install needed) that parses, describes, deep-validates, and computes next fire times. ## When to Use This Skill - Use when a user writes, edits, reviews, or deploys a cron expression — in a crontab, a Kubernetes `CronJob`, a GitHub Actions `schedule`, an Airflow DAG, a Celery beat schedule, a systemd timer, or any scheduled task. - Use when debugging a job that "didn't fire" or "fired at the wrong time." - Use when a user asks "what does this cron expression mean?" or "when will this run next?" or "how often does this run per year?" - Use when reviewing a CI/CD pipeline or infrastructure config that contains a `schedule` field. - Use wh
- Overview
- When to Use This Skill
- How It Works
- Step 1: Parse the expression
- Step 2: Describe it in plain English
- Step 3: Run the trap checklist
- Step 4: Calculate next runs and annual fire count
- The Five Cron Death-Traps
- 1. Impossible dates — the "never fires" bug
- 2. OR-semantics — the "fires too often" bug
- 3. Midnight spike — the "everything at once" bug
- 4. Uneven steps — the "drift" bug
- 5. Leap-year February 29 — the "annual surprise"
- Using the validation script
CLI (via the bundled wrapper) node scripts/cli.js describe "*/5 * * * *" node scripts/cli.js validate "0 0 30 2 *" node scripts/cli.js next "0 9 * * 1-5" 5
What does the cron-doctor skill do?
Diagnose and validate cron expressions before they ship. Catches the five silent death-traps: impossible dates that never fire, OR-semantics that fire too often, midnight spikes, uneven step drift, and leap-year February 29.
How do I install it?
Run `npx skills add sickn33/agentic-awesome-skills --skill cron-doctor --agent claude-code` — it drops the skill into your project so the agent can pick it up. Swap the --agent value for codex, cursor or copilot if you use one of those.
Where does this skill come from?
From sickn33/agentic-awesome-skills, a repository with 44,414 stars. We read it straight from the repository tree rather than a submitted listing, so what you see here is what is actually published.
Is a popular skill a good skill?
Not necessarily. Stars measure attention, not adoption — a repository can trend for a week and be abandoned. That is why we show the weekly change from our own snapshots next to the total, instead of a single flattering number.