*/30 * * * * *
Cron reads this as: every 30th second, every minute.
This is a Quartz-style expression with seconds in the leading field. Standard Unix cron takes five fields and has a one-minute floor, so it will reject this line. See Quartz vs Unix cron for the differences.
Next 5 runs
Computed in your browser's local time zone. Cron itself evaluates against the server's zone, which on most cloud hosts is UTC — see time zones & DST if that distinction matters here.
- Calculating…
When to use this schedule
Six fields with seconds first — a Quartz-style expression, supported by Spring's @Scheduled, Quartz itself and several other JVM schedulers. Standard Unix cron cannot do this at all.
What to watch out for
Standard cron's floor is one minute, so this expression will be rejected outright by a Unix crontab. If you are on plain cron and need sub-minute work, the usual workaround is a single minute-level job that loops internally with a sleep, or better, a long-running process with its own timer. At 30-second intervals, overlap is the dominant risk: make sure the work reliably completes in well under 30 seconds, or guard it with a lock.
The crontab line
*/30 * * * * * /usr/local/bin/your-job.sh >> /var/log/your-job.log 2>&1Redirect the output somewhere you will actually read it — by default cron mails it, and on a host with no mail transport that means it is discarded. See the crontab guide for the surrounding syntax.
Related schedules
| Expression | Schedule |
|---|---|
0/30 * * * * ? | The same schedule in Quartz notation |
*/10 * * * * * | Every 10 seconds |
* * * * * | Every minute — standard cron |
Build your own
Need something this page does not cover? Compose it field by field in the visual builder, or paste an expression you already have into the explainer for a per-field breakdown. The examples library collects sixty schedules in one place, and the guides cover crontab syntax, time zones, troubleshooting and production practices.