Cron expression explainer

How to understand a cron expression

1. Type or paste your cron expression into the input field (e.g. 0 9 * * 1-5).
2. The tool translates it into plain English instantly.
3. View the next 5 scheduled run times based on the expression.
4. Use the quick-fill buttons to start with a common schedule like @daily or @weekly.

Common uses

• Verifying that a cron job is scheduled at the intended time before deploying, use Unix timestamp converter to check the exact epoch time of a past run
• Explaining a cron expression to a colleague who is not familiar with the syntax
• Debugging why a scheduled task ran at an unexpected time. The date calculator helps work out how many days ago or until a specific date

Technical specification

• Algorithm or formula: Plain-English translation uses the cronstrue library. Next-run preview is a custom 5-field parser that checks every field and expands ranges, lists, step values, and month and day names, then walks forward through the matching days minute by minute to find the next matching slots.
• Browser API or library: cronstrue 3.14 (about 22 KB minified, 6 KB gzipped), imported with a dynamic import when the page opens. Native JavaScript Date for time arithmetic.
• Input limits: Standard 5-field cron syntax, including month names (JAN to DEC) and day names (SUN to SAT), plus the @hourly, @daily, @midnight, @weekly, @monthly, @yearly, and @annually shorthands. Quartz 6 and 7-field expressions (seconds first) get a description but no next-run preview.
• Output: Plain-English description and the next 5 run times in the browser's local time zone, looking up to 5 years ahead.
• Known limitations: At daylight saving changes the preview follows Vixie cron: a job with a fixed minute and hour is listed once when the clocks go back, and a run at a time the clocks skip is listed at the first minute after the change. A job with * in the minute or hour field is listed at each matching time the clock shows. The Quartz characters L, W, and # get a description but no next-run preview, and ? is read as *.

Frequently asked questions

What is a cron expression?

A cron expression is a string of 5 fields separated by spaces that defines a recurring schedule: minute, hour, day of month, month, and day of week. For example, 0 9 * * 1-5 means 9:00 AM every weekday.

Is my data sent to a server?

Parsing and scheduling calculations run entirely in your browser using JavaScript. Our servers are not involved at any point.

Does the tool support @daily and other shorthand expressions?

Yes. Common shortcuts like @hourly, @daily, @weekly, @monthly, and @yearly are all supported.

What time zone are the next run times shown in?

Run times are shown in your browser's local time zone, and each one is labelled with its zone name or UTC offset.