Cron expression for every 30 minutes

*/30 * * * *

Twice an hour, on the hour and at half past, forty-eight times a day.

Runs when: every 30 minutes; every hour; 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	`*/30`	every 30 minutes
Hour	`*`	every value
Day of month	`*`	every value
Month	`*`	every value
Day of week	`*`	every value

The next five runs

What people use it for

Exporting analytics to a warehouse
Sending reminder emails
Clearing temporary files

Two ways to write the same thing

*/30 and 0,30 give identical schedules. That is harmless, but teams that mix both in one crontab often waste time during a review wondering whether they differ. Choose one style and keep it. If you want to avoid the busy :00 and :30 marks, use 5,35 or 12,42.

Variations of every 30 minutes

Expression	What it does
`5,35 * * * *`	Twice an hour, at :05 and :35.
`/30 9-17 * 1-5`	Every 30 minutes during business hours on weekdays.
`0,30 8-20 * * *`	Every 30 minutes from 08:00 to 20:30.

The same schedule in four tools

Linux crontab

*/30 * * * * /path/to/command

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

Kubernetes CronJob

spec:
  schedule: "*/30 * * * *"
  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: '*/30 * * * *'

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(0/30 * * * ? *)

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 30 minutes

Is */30 the same as 0,30?: Yes, they give the same schedule. Use whichever your team reads faster.
How do I run something every 45 minutes?: Cron cannot do a true 45-minute interval. */45 fires at :00 and :45 of each hour, which leaves gaps of 45 and then 15 minutes. For an even interval, use a systemd timer or a loop with a sleep.

Nearby schedules

Cron expression for every 15 minutes: Four runs an hour.
Cron expression for every hour: One run an hour, at :00.
All schedules and the generator

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