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◷ Cron expression explainer

The cron expression */20 * * * * means: every 20 minutes. In UTC its next runs are Mon 2026-10-12 20:20 and Mon 2026-10-12 20:40. A heartbeat monitor with a 10-minute grace period, pinged at the end of each run, alerts you when the job stops running or fails silently.

Paste a 5-field cron expression. Get what it means in plain English, when it runs next, and what could go wrong. Nothing is sent anywhere; it runs on our server in a few milliseconds.

Try: */5 * * * * (every 5 minutes) · 0 9 * * 1-5 (weekdays 09:00) · 0 0 1 * * (monthly) · 30 2 * * 0 (Sundays 02:30) · 0 9 1-7 * 1 (the OR trap) · @daily (macro)
*/20 * * * *
Every 20 minutes.
minutehourday of monthmonthday of week
*/20****
0, 20, 4024 values31 values1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 120, 1, 2, 3, 4, 5, 6

Next 10 runs · UTC

  1. Mon 2026-10-12 20:20 UTC (+00:00) · in 11m
  2. Mon 2026-10-12 20:40 UTC (+00:00) · in 31m
  3. Mon 2026-10-12 21:00 UTC (+00:00) · in 51m
  4. Mon 2026-10-12 21:20 UTC (+00:00) · in 1h 11m
  5. Mon 2026-10-12 21:40 UTC (+00:00) · in 1h 31m
  6. Mon 2026-10-12 22:00 UTC (+00:00) · in 1h 51m
  7. Mon 2026-10-12 22:20 UTC (+00:00) · in 2h 11m
  8. Mon 2026-10-12 22:40 UTC (+00:00) · in 2h 31m
  9. Mon 2026-10-12 23:00 UTC (+00:00) · in 2h 51m
  10. Mon 2026-10-12 23:20 UTC (+00:00) · in 3h 11m

Times are UTC, which is what most cloud servers and GitHub Actions use. Set a timezone above to see local times.

Watch out

✓ No gotchas specific to this expression.

Always true for crontab: it runs in the server's timezone (check with date), with a minimal PATH, and % must be escaped as \%.
Full guide with systemd, Kubernetes and GitHub Actions examples: Every 20 minutes

Monitor this job

cron never tells you when a job stops running. Add a heartbeat ping after the command: Vigil expects it on this schedule and alerts you if it doesn't arrive within the grace period (we'd suggest 10 minutes here).

crontab -e
*/20 * * * * /usr/local/bin/my-job.sh && curl -fsS -m 10 --retry 3 -o /dev/null https://puzaricloud.in/ping/<your-token>
Report start, finish and exit code (catches failures and hangs, not just silence)
*/20 * * * * curl -fsS -m 10 -o /dev/null https://puzaricloud.in/ping/<your-token>/start; /usr/local/bin/my-job.sh; curl -fsS -m 10 --retry 3 -o /dev/null https://puzaricloud.in/ping/<your-token>/$?

Replace /usr/local/bin/my-job.sh with your command and <your-token> with the token Vigil gives you. && means the ping only goes out when the job succeeded.

Watch this schedule — get alerted if it doesn't run

Link to this result:
How Vigil can watch this for you

Know the moment a cron job doesn't run

Paste the same expression into a Vigil heartbeat. Vigil works out when each run is due in your timezone, waits the grace period, then alerts you if the ping never came, if the job reported a failure, or if it started and never finished.

Monitor a cron job free
Free plan, no card. Alerts on email, Telegram, Slack, Discord, Teams or any webhook.
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