Run a cron job every 3 hours
“At minute 0 past every 3rd hour.”
Eight runs a day at 00, 03, 06, 09, 12, 15, 18, 21. Three-hour spacing divides the day evenly, which keeps 'runs per day' math simple for quota planning — and it is a divisor of 24, so the schedule never drifts across days like a 5- or 7-hour step would.
0 */3 * * *Next 5 runs
Computing from your local clock…
Field by field
| Field | Value | Meaning |
|---|---|---|
| Minute | 0 | exactly 0 |
| Hour | */3 | every 3 starting from 0 |
| Day of month | * | every value |
| Month | * | every value |
| Day of week | * | every value |
Typical uses
- Backing up frequently-changing small datasets
- Polling slow-moving external feeds (exchange rates, weather)
- Compacting append-only storage
Worth knowing: Steps that do not divide 24 evenly (*/5, */7 in hours) produce an uneven gap at midnight — the sequence resets at hour 0 every day.
Related schedules
Need a different schedule? Build and test any cron expression with live explanation and next-run preview, or read the complete cron syntax guide.