How to Use the Cron Expression Generator & Explainer

What the tool does

A standard cron expression has five fields: minute (0 to 59), hour (0 to 23), day of month (1 to 31), month (1 to 12 or JAN to DEC) and day of week (0 to 7 or SUN to SAT, where 0 and 7 are both Sunday). An asterisk means every value, a comma makes a list, a dash makes a range, and a slash makes a step, as in */5. Shortcuts such as @daily, @hourly, @weekly, @monthly and @yearly also work.

How to use it

1. Type or paste an expression, or pick a preset such as Every 5 minutes or Weekdays at 8:00 AM.
2. Or open Build an expression and choose the schedule. The expression updates as you choose.
3. Read the plain-English meaning and the next run times in the time zone you pick.

A worked example

The expression 0 8 * * 1-5 means at 8:00 AM, Monday through Friday. The expression */15 * * * * means every 15 minutes. The next run times show when each will fire next, so you can confirm the schedule matches what you meant before you put it in a server.

Things to know

• Day of month and day of week work together in a way that surprises people. If both are restricted (neither starts with an asterisk), cron runs when either one matches. If either starts with an asterisk, both must match.
• This is standard 5-field cron as used by Linux and Unix crontab. Quartz, Spring and AWS EventBridge add fields or symbols and are not supported.
• Next runs look up to 10 years ahead. A schedule that never occurs, such as February 31, shows no runs.
• Schedulers differ in how they handle daylight-saving changes. Check yours.

Common questions

Why did my job run on days I did not expect? Probably the day-of-month and day-of-week rule. When both are set, cron runs the job if either matches.

Does it support a seconds field? No. It handles the standard five fields only.

Cron Expression Generator: Open the Cron Expression Generator & Explainer and try your own numbers.