Cheat Sheets · Cron Cheat Sheet · Cron Every 3 Hours — Crontab Example

Cron Every 3 Hours — Crontab Example

0 */3 * * *

Runs at minute 0 every 3 hours (00:00, 03:00, 06:00, 09:00, 12:00, 15:00, 18:00, 21:00).

Field by field

Field	Value	Meaning
`Minute`	`0`	At minute 0
`Hour`	`*/3`	Every 3rd hour (0, 3, 6, 9, 12, 15, 18, 21)
`Day of month`	`*`	Every day
`Month`	`*`	Every month
`Day of week`	`*`	Every day of the week

Dividing the 24-hour day into 8 equal windows gives you runs at 00:00, 03:00, 06:00, 09:00, 12:00, 15:00, 18:00, and 21:00. This is popular for batch feeds and analytics checkpoints.

0 */3 * * * /usr/local/bin/batch-check.sh

Related schedules

0 */2 * * * Every 2 hours 0 */6 * * * Every 6 hours 0 */4 * * * Every 4 hours

FAQ

How do I offset by 15 minutes?
Change the minute field: 15 */3 * * * fires at 00:15, 03:15, 06:15… avoiding :00 congestion.

Can I run only during daytime?
Use an explicit range or list: 0 9-18/3 * * * runs at 09:00, 12:00, 15:00, and 18:00.

Is 0,3,6,9,12,15,18,21 the same as */3?
Yes, exactly identical. The step syntax */3 is the concise shorthand.

Stop memorizing — build it interactively

Try this schedule in the Cron Editor

Full reference: Cron Cheat Sheet