Cron Expression Generator

Translate a cron expression into plain English and preview its next run times — including the day-field OR rule most tools get wrong.

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Cron expression

Meaning and next runs

Output appears here as you type.

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About the Cron Expression Generator

Builds a five-field cron expression and states in plain English which times it selects, which is the check worth doing before deploying a schedule. Cron syntax is easy to write and genuinely hard to read back.

The classic trap is the two day fields. When both day-of-month and day-of-week are restricted, cron runs the job when *either* matches, so `0 9 1-7 * 1` fires on the first seven days and every Monday — about 76 times a year rather than 12. A field starting with `*`, including `*/2`, counts as unrestricted.

Frequently asked questions

What do the five fields mean?

In order: minute (0–59), hour (0–23), day of month (1–31), month (1–12 or JAN–DEC) and day of week (0–6 or SUN–SAT, where both 0 and 7 mean Sunday). Each accepts *, a single value, a range (1-5), a list (1,3,5) and a step (*/15).

Why does "0 0 1 * MON" run more often than I expect?

Because of a rule that surprises nearly everyone: when BOTH the day-of-month and day-of-week fields are restricted, cron fires if EITHER matches — not both. So that expression runs on the 1st of every month AND on every Monday. If you need "the first Monday", cron alone cannot express it; you have to check the date inside your job.

Which timezone does cron use?

Whatever the machine or scheduler is configured with, and this is a common source of production incidents. System crontab typically uses the server's local time, which means jobs shift by an hour twice a year under daylight saving — and a 2:30am job may run twice or not at all on the transition days. Running schedulers in UTC avoids the whole class of bug.

Are shorthand aliases supported?

Yes — @hourly, @daily, @midnight, @weekly, @monthly and @yearly/@annually are all accepted and expanded to their five-field equivalents.