A cron expression schedules recurring tasks — backups, reports, cleanups — on Unix-like systems. This builder lets you assemble a valid five-field cron schedule one field at a time, or start from a preset, and shows a plain-English summary so you can be sure it does what you intend before pasting it into a crontab.
How it works
A standard cron expression has five space-separated fields, read left to right:
| Field | Range | Meaning |
|---|---|---|
| Minute | 0–59 | minute of the hour |
| Hour | 0–23 | hour of the day |
| Day of month | 1–31 | day of the month |
| Month | 1–12 | month of the year |
| Day of week | 0–6 | 0 = Sunday |
Each field accepts * (every value), a single number, a list (1,15), a range (1-5), or a step (*/5). The builder validates each entry against its range, flags out-of-range values, and translates the whole expression into a sentence as you type.
Building common schedules
To run a job at 9:00 every Monday:
0 9 * * 1→ “At 09:00 on Monday”
Other common patterns:
| Expression | What it does |
|---|---|
*/5 * * * * | Every 5 minutes |
0 0 * * * | Daily at midnight |
0 0 1 * * | First of every month at midnight |
0 8-18 * * 1-5 | Every hour from 08:00 to 18:00 on weekdays |
15 3 * * 0 | 03:15 every Sunday |
Reading your crontab — common gotchas
Day-of-week numbering: 0 and 7 both mean Sunday in most Unix implementations, so 0 9 * * 0 and 0 9 * * 7 are equivalent. Some CI tools number Monday as 1 and Sunday as 7 in ISO order — the builder names the day in its English summary so you can confirm.
Both day fields set at once: when both day-of-month and day-of-week are not *, standard cron fires when either matches, not both. 0 9 15 * 1 fires at 09:00 on every 15th of the month and at 09:00 every Monday. To fire only on, say, Mondays that fall on the 15th, you need to handle that logic inside the job itself.
Time zones: the cron daemon uses the server’s local time. Most cloud servers run UTC, so a job you intend to fire at 09:00 local time should be offset accordingly. For example, UTC+5:30 (IST) means writing 30 3 * * * to trigger at 09:00 IST.
Minimum resolution: standard cron fires at most once per minute. Sub-minute scheduling requires a different tool or a sleep loop inside the job.
Where to paste the expression
Copy the finished five-field string directly into:
/etc/cron.d/files orcrontab -eon Linux/macOS- The
schedule:key in GitHub Actions workflows - The
spec:field of a Kubernetes CronJob manifest - Cloud scheduler consoles (GCP Cloud Scheduler, Azure Logic Apps, etc.)
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