0 */4 * * *. Six runs per day at 00:00, 04:00, 08:00, 12:00, 16:00 and 20:00. A common cadence for cache refreshes and twice-an-8-hour-shift jobs.View future cron matches in a calendar
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0 */4 * * *
The hour step */4 selects 0, 4, 8, 12, 16, 20 — six firings per day. Four is a divisor of 24 so the spacing is exactly 4 hours.
See the dedicated guide for the full breakdown: Cron every hour.
Paste it into the editor above to see the next runs on a calendar.
0 */4 * * 1-5 — every 4 hours on weekdays only30 */4 * * * — every 4 hours at xx:30 (00:30, 04:30, 08:30, …)0 */4 * * * uses standard 5-field cron syntax, so it works in:
crontab — 0 */4 * * * /path/to/script.shvercel.json.cron(...) with day-of-week as ? and a year field.0) and append day-of-week ?.`0 */4 * * *`. Paste this into any cron-compatible scheduler (Linux crontab, AWS EventBridge, Vercel cron, Quartz, node-cron, robfig/cron) to run a job every 4 hours.
The editor above shows the next 30+ runs on a calendar in your local timezone, plus a plain-English description. If the calendar matches your intent, the cron is correct.
It uses standard 5-field cron syntax, so yes — Linux crontab, AWS EventBridge (with the additional `?` and year fields), Vercel cron jobs, Quartz Scheduler, node-cron, robfig/cron, and Kubernetes CronJob all accept it. Vercel's free Hobby plan caps the minimum frequency at once-per-day; the Pro plan removes that cap.
Most schedulers will start the new run anyway, leading to overlap. To prevent this, wrap the command with `flock -n /tmp/myjob.lock /path/to/script.sh` on Linux, or set `concurrencyPolicy: Forbid` on Kubernetes CronJob. Vercel cron and AWS EventBridge let you configure concurrency at the platform level.
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