Cron expression generator — build a crontab schedule from menus

How to use the cron generator

1. Choose a Minute mode: every minute, every N minutes, or at fixed minutes. Type the number or list in Minute value (15, or 0,30).
2. Choose an Hour mode: every hour, every N hours, at fixed hours (9 or 9,17), or Between hours (9-17). Enter it in Hour value.
3. Pick Day of week: every day, Monday to Friday, Saturday and Sunday, or Specific days (0 or 7 = Sunday, 1 = Monday … 6 = Saturday).
4. Leave Day of month and Month as *, or narrow them (1,15 or 1-6 or JAN,MAR).
5. Choose a Time zone for the preview. The expression, its plain-English meaning and the next five runs update as you type.

What it does and when to use it

Cron syntax is short but easy to get wrong: is the hour field second or third, and is Sunday 0 or 7? This tool builds the line from choices you can read. Use it for a crontab entry, a Kubernetes CronJob schedule or a GitHub Actions on.schedule; all take the same 5-field format.

To go the other way and read an expression someone else wrote, use the Cron Parser. To type each field by hand and see it explained, use Crontab Guru.

How it works

The menus map to the five fields of a POSIX crontab line, in this order:

minute  hour  day-of-month  month  day-of-week

“Every” writes *, “Every N” writes */N, and fixed values or ranges are copied as typed. Monday to Friday becomes 1-5, the weekend 0,6. The line is then checked with the cron-parser library, described with cronstrue and stepped forward from now to list five runs, all in your browser.

Worked examples

Weekday morning report. Minute “At minute(s)” 30, Hour “At hour(s)” 9, Day of week “Monday to Friday”:

30 9 * * 1-5
Schedule: At 09:30, Monday through Friday

Polling during office hours. Minute “Every N minutes” 15, Hour “Between hours” 9-17, every day:

*/15 9-17 * * *
Schedule: Every 15 minutes, between 09:00 and 17:59
Runs in the next 24 hours: 36

The first-Monday trap. Minute 0, Hour 3, Specific days 1, Day of month 1-7 gives 0 3 1-7 * 1. The tool warns that the job runs when either field matches, so it fires on the 1st to 7th and on every Monday. A common fix is 0 3 1-7 * * plus a weekday test inside the script.

Limits and tips

• The Minute value, Hour value, Day of month and Month boxes are passed through as typed. Out-of-range values such as minute 75 show an “Invalid cron expression” message instead of a schedule.
• The preview library also accepts extras like L (last day of the month) in Day of month. Classic Vixie cron and many hosted schedulers do not, so check your platform’s docs.
• A job that must run at an exact UTC instant is safest with a UTC server clock; compare zones in Timezone Dev.