Cron expression generator

Cron schedules you can read

Cron is the scheduler built into Linux and Unix systems, and its notation has spread to cloud schedulers, CI pipelines, container platforms, backup tools and many applications. A schedule such as */15 9-17 * * 1-5 is compact but cryptic, and a misplaced field can mean a job that runs every minute instead of every hour, or never. This tool lets you build the expression without memorizing the syntax and tells you in plain words what it will do.

The five fields

• Minute from 0 to 59.
• Hour from 0 to 23, on a 24-hour clock.
• Day of the month from 1 to 31.
• Month from 1 to 12, or the names JAN to DEC.
• Day of the week from 0 to 7, where 0 and 7 are Sunday, or the names SUN to SAT.

In each field an asterisk means every value, a comma separates a list (1,15), a hyphen sets a range (9-17) and a slash sets a step (*/10 is every ten). They can be combined, as in 0-30/10 for minutes 0, 10, 20 and 30.

Check the next runs

The clearest way to be sure a schedule is right is to see when it will actually fire. The tool lists the next five run times in the time zone of your browser. Remember that the server that runs the job may use another time zone, often UTC, so check which one your system uses.

A classic trap

When both the day of the month and the day of the week are restricted, standard cron runs the job when either of them matches, not both. So 0 9 1 * 1 runs on the first of the month and also on every Monday. The tool warns you when you set both.

What it does not cover

This is standard five-field cron. It does not handle a seconds field, Quartz or Spring extensions such as L, W and #, or special strings such as @daily, which some systems accept as shortcuts. The explanation is a guide, so test important schedules on your system. Everything is calculated in your browser. To convert a date to a timestamp, use the Unix timestamp converter.