Cron expression for every 6 hours

0 */6 * * *

The job runs at minute 0 of hours 0, 6, 12 and 18, four times a day.

Runs when: minute 0; every 6 hours; every day of month; every month; any day of week.

Change it in the cron expression generator

How the five fields read

Field	Value	Reads as
Minute	`0`	at 0
Hour	`*/6`	every 6 hours
Day of month	`*`	every value
Month	`*`	every value
Day of week	`*`	every value

The next five runs

What people use it for

Refreshing a data warehouse extract
Rotating and compressing logs
Syncing a supplier or product feed

The hours are fixed to the clock

*/6 in the hour field always means 0, 6, 12 and 18, whatever time you deployed it. To move the whole pattern, give the field a start: 0 2-23/6 * * * runs at 02:00, 08:00, 14:00 and 20:00. Remember too that those hours are in the scheduler's time zone, so a server on UTC fires at 00:00 UTC, which is 05:00 in a UTC+5 time zone such as Pakistan.

Variations of every 6 hours

Expression	What it does
`0 2-23/6 * * *`	Every 6 hours starting at 02:00: 02:00, 08:00, 14:00 and 20:00.
`30 /6 * *`	Every 6 hours at :30 past: 00:30, 06:30, 12:30 and 18:30.
`0 /8 * *`	Every 8 hours instead: 00:00, 08:00 and 16:00.

The same schedule in four tools

Linux crontab

0 */6 * * * /path/to/command

Add it with crontab -e. It runs in the machine's time zone.

Kubernetes CronJob

spec:
  schedule: "0 */6 * * *"
  timeZone: "Etc/UTC"
  concurrencyPolicy: Forbid

timeZone is stable from Kubernetes 1.27. Without it, the controller's time zone applies. Forbid stops a new run starting while the last one is still going.

GitHub Actions

on:
  schedule:
    - cron: '0 */6 * * *'

Schedules run in UTC from the default branch, and a run can start a few minutes late when GitHub is busy. Scheduled workflows in public repositories are disabled after 60 days without repository activity.

AWS EventBridge

cron(0 0/6 * * ? *)

EventBridge uses six fields, with a question mark in one of the two day fields, and rules run in UTC. Weekday numbers start at Sunday = 1, so names such as MON are safer than numbers.

Questions about every 6 hours

Why does every 5 hours behave oddly?: 24 does not divide by 5, so 0 */5 * * * runs at 00:00, 05:00, 10:00, 15:00 and 20:00, then starts over at 00:00. The last gap is four hours, not five.
Can it start counting from the time I deployed?: No. Cron is tied to the clock, not to when the job was created. If you need an interval measured from a start time, use a scheduler with a rate or interval setting.

Nearby schedules

Cron expression for every hour: Twenty-four runs a day.
Cron expression for twice a day: Two runs a day, at hours you choose.
All schedules and the generator

Scheduling jobs, pipelines and cloud infrastructure is part of my DevOps engineering work.