Cron every 30 minutes during business hours: the expression, explained, in Node.js
The cron expression for “every 30 minutes during business hours” is */30 9-17 * * 1-5. This page shows what each field does, the next five times it will fire, the mistake most people make with it, and a working Node.js example you can paste.
The expression
| Field | Value | Meaning |
|---|---|---|
| minute | */30 | every 30 minutes, starting at 0 |
| hour | 9-17 | from 9 to 17 |
| day of month | * | every day of month |
| month | * | every month |
| day of week | 1-5 | Monday to Friday |
Next five runs (UTC, from now)
- 2026-09-18 09:00 UTC
- 2026-09-18 09:30 UTC
- 2026-09-18 10:00 UTC
- 2026-09-18 10:30 UTC
- 2026-09-18 11:00 UTC
Mistakes people make with this schedule
- "9-17" includes the whole of hour 17, so the last run of the day is at 17:45, not 17:00, and the first is at 09:00. Use "9-16" if 17:00 must be the last.
- Assuming the server clock is your clock. Cron runs in the machine’s timezone unless the runtime says otherwise; the examples here are UTC.
- No lock around a job that might overlap itself, and no alert when it silently stops. That second one is what Supercrontab is for.
Run it in your stack
import cron from 'node-cron';
cron.schedule('*/30 9-17 * * 1-5', async () => {
await runReport();
}, { timezone: 'UTC' });In-process schedulers die with the process. Fine for one long-lived server, not for serverless.
Questions
Does */30 9-17 * * 1-5 run in my local time?
Only if the scheduler is configured for it. crontab uses the system timezone; Vercel and GitHub Actions always use UTC; Laravel and node-cron take a timezone option. In Supercrontab the timezone is a field on the job.
What if the previous run is still going?
Classic cron starts the next run anyway. Add a lock (flock on Linux, withoutOverlapping() in Laravel) or let Supercrontab skip the tick while the previous request is open.
Is there a shorter way to write this?
No. The five-field form is the shortest portable version.