◷ Cron expression explainer
The cron expression 0 */4 * * * means: at 00:00, 04:00, 08:00, 12:00, 16:00 and 20:00, every day. In UTC its next runs are Tue 2026-10-13 00:00 and Tue 2026-10-13 04:00. A heartbeat monitor with a 30-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.
| minute | hour | day of month | month | day of week |
|---|---|---|---|---|
| 0 | */4 | * | * | * |
| 0 | 0, 4, 8, 12, 16, 20 | 31 values | 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 | 0, 1, 2, 3, 4, 5, 6 |
Next 10 runs · UTC
- Tue 2026-10-13 00:00 UTC (+00:00) · in 3h 52m
- Tue 2026-10-13 04:00 UTC (+00:00) · in 7h 52m
- Tue 2026-10-13 08:00 UTC (+00:00) · in 11h 52m
- Tue 2026-10-13 12:00 UTC (+00:00) · in 15h 52m
- Tue 2026-10-13 16:00 UTC (+00:00) · in 19h 52m
- Tue 2026-10-13 20:00 UTC (+00:00) · in 23h 52m
- Wed 2026-10-14 00:00 UTC (+00:00) · in 1d 3h
- Wed 2026-10-14 04:00 UTC (+00:00) · in 1d 7h
- Wed 2026-10-14 08:00 UTC (+00:00) · in 1d 11h
- Wed 2026-10-14 12:00 UTC (+00:00) · in 1d 15h
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.
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 30 minutes here).
0 */4 * * * /usr/local/bin/my-job.sh && curl -fsS -m 10 --retry 3 -o /dev/null https://puzaricloud.in/ping/<your-token>
0 */4 * * * 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.
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.