What is the cron expression for every 30 minutes?

The cron expression for every 30 minutes is "*/30 * * * *". Runs on the hour and the half hour.

What should I watch out for when running a cron job every 30 minutes?

Runs land at :00 and :30 — the :00 run collides with every hourly job on the same machine. 7,37 * * * * is the same cadence minus the contention. Across a DST transition the wall-clock times stay :00/:30 but the UTC times of your runs shift by an hour — watch out if a downstream system compares timestamps in UTC.

Cron expression for Every 30 minutes

*/30 * * * *

Runs on the hour and the half hour.

Next 5 runs (your local time)

These are shown in your browser’s timezone. The job itself runs in the scheduler’s timezone — often UTC — so the real run time can differ.

What people actually schedule with `/30 * * *`

Regenerating sitemaps or RSS feeds on active sites
Snapshotting a small database to object storage during business hours
Refreshing short-lived API tokens that expire hourly

Use `/30 * * *` on your platform

It’s the same 5-field expression everywhere — what changes is where you put it and which timezone it runs in.

Linux / crontab

*/30 * * * * /path/to/your-command

Runs in the server’s local timezone — check it with timedatectl. Full field reference: crontab(5) man page.

GitHub Actions

on:
  schedule:
    - cron: "*/30 * * * *"

GitHub Actions always runs scheduled jobs in UTC — there is no timezone setting, and runs can be delayed under load (official docs).

Kubernetes CronJob

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

Defaults to UTC. Set spec.timeZone (Kubernetes 1.27+) for a specific zone — see the CronJob docs.

Quartz / Spring `@Scheduled`

Quartz uses 6 fields (seconds first): 0 */30 * * * *. Watch out: Quartz day-of-week is 1=SUN … 7=SAT (not 0–6), and day-of-month / day-of-week use ? — double-check if your schedule touches those fields (Quartz cron reference).

Gotchas with every 30 minutes schedules

Runs land at :00 and :30 — the :00 run collides with every hourly job on the same machine. 7,37 * * * * is the same cadence minus the contention.
Across a DST transition the wall-clock times stay :00/:30 but the UTC times of your runs shift by an hour — watch out if a downstream system compares timestamps in UTC.

Will you know if this job silently fails?

Cron jobs fail quietly — a server reboots, a path changes, or an error code is ignored — and nobody notices until the data is missing. A cron monitor (a dead-man’s-switch) alerts you when a scheduled job does not check in on time.

Monitor your cron jobs with UptimeRobot →

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Is `/30 * * *` the right schedule?

If results are only read once a day, hourly or even daily is plenty. Every 15 only earns its keep under a real SLA.

Or use the interactive cron generator & explainer, read the complete cron syntax guide, or pick another common schedule: