Cron expression for every 2 hours

The cron expression 0 */2 * * * runs a job every 2 hours on the hour — at 00:00, 02:00, 04:00, 06:00, 08:00, 10:00, 12:00, 14:00, 16:00, 18:00, 20:00 and 22:00 (12 firings per day). The */2 is step syntax: “every 2 units starting from 0”. The step works in any cron field; */2 in the day-of-month field would mean “every other day”, */2 in the minute field means “every other minute”.

Quick reference

How does step syntax (*/N) work?

*/N reads as “every N units starting from the lowest legal value of this field”. In the minute field (range 0–59), */15 hits 0, 15, 30, 45. In the hour field (range 0–23), */2 hits 0, 2, 4, …, 22. In the day-of-month field (range 1–31), */5 hits 1, 6, 11, 16, 21, 26, 31.

The “starting from 0” matters when N is not a divisor of the field’s range. For divisors of 24 — */2, */3, */4, */6, */8, */12 — the firings are evenly spaced across the day. For non-divisors — */5, */7, */9, */11 — there’s a gap at the day boundary because the count restarts at hour 0.

For example, */5 * * * in the hour field fires at 0, 5, 10, 15, 20. Then the day rolls over and the next firing is at hour 0 of the next day — a 4-hour gap, not 5.

If you want truly evenly-spaced “every N hours” and N is not a divisor of 24, you can’t get it with cron alone. Use a long-running scheduler that tracks elapsed time, or accept the day-boundary gap.

Variations

How do I use it on each platform?

Linux crontab:

0 */2 * * * /usr/local/bin/health-check

Kubernetes CronJob:

apiVersion: batch/v1
kind: CronJob
metadata:
  name: health-check
spec:
  schedule: "0 */2 * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: check
              image: my-org/health-check:1.0
          restartPolicy: OnFailure

AWS EventBridge:

aws events put-rule \
  --name health-check \
  --schedule-expression "cron(0 0/2 * * ? *)"

EventBridge’s rate(2 hours) is an alternative that fires every 2 hours from rule-creation time — no clock alignment. Use cron() for clock-aligned 00:00, 02:00, 04:00; use rate() if you don’t care about the wall-clock minute.

GitHub Actions:

on:
  schedule:
    - cron: '0 */2 * * *'

Common mistakes

Expecting */5 in the hour field to be evenly spaced across the day boundary. It hits 0, 5, 10, 15, 20 — then resets to 0 the next day, leaving a 4-hour gap. If you need “every 5 hours from when the job was created”, use a rate() expression or a long-running scheduler.

Putting the step in the wrong field. */2 * * * * (step in MINUTE field) means every 2 minutes — 720 runs per day. 0 */2 * * * is what you want for every 2 hours. Easy mis-paste.

Using 0 */2 * * ? * in AWS without 0/2. Both work in modern AWS, but the older docs say only 0/2 is valid. For maximum compatibility with old IaC validators and copy-paste guides, prefer 0/2.

For other schedules see common cron schedules, or build a custom expression with the Cron Expression Builder.