Cron Expression Parser & Builder

How to use: step by step

1. 1
   Choose Build or Parse mode
   Build mode lets you construct a cron expression using dropdowns. Parse mode lets you enter an existing expression and decode it.
2. 2
   Set each field (Build mode)
   Use the Minute, Hour, Day of Month, Month, and Day of Week selectors. Each field supports Every, Specific value, Step (*/n), or Range.
3. 3
   Read the generated expression
   The result panel shows the cron expression and a human-readable description like 'Runs every 15 minutes, weekdays 9:00–17:59'.
4. 4
   Paste an expression (Parse mode)
   Switch to Parse mode and type or paste any 5-field cron expression. The tool breaks down each field and explains it in plain English.
5. 5
   Check the next 5 execution times
   The Next Executions panel shows the upcoming 5 run times based on your local system clock: useful for verifying the schedule is what you intended.

Frequently Asked Questions

What is a cron expression?

A cron expression is a string of 5 (or 6) space-separated fields that define a recurring schedule for automated tasks. The standard 5-field format is: minute hour day-of-month month day-of-week. For example, '0 9 * * 1-5' means 'at 9:00 AM, Monday through Friday'.

What do the 5 fields in a cron expression mean?

From left to right: (1) minute (0–59), (2) hour (0–23), (3) day of month (1–31), (4) month (1–12), (5) day of week (0–6, where 0 is Sunday). An asterisk (*) means 'every value'. A slash (*/n) means 'every n units'. A hyphen (a-b) means 'range from a to b'.

What does */15 mean in a cron expression?

*/15 in the minute field means 'every 15 minutes': specifically at minutes 0, 15, 30, and 45 of every hour. The slash is a step operator: */n means every nth value starting from the minimum.

How do I run a job every weekday at 9 AM?

Use the expression '0 9 * * 1-5'. This means: minute 0, hour 9, every day-of-month, every month, Monday through Friday (1–5).

What is the difference between day-of-month and day-of-week fields?

Day-of-month (field 3) triggers based on the calendar date (1–31). Day-of-week (field 5) triggers based on the day name (0=Sunday, 6=Saturday). When both are specified, most cron implementations run the job if either condition is true (OR logic).

Does this tool support 6-field cron expressions with seconds?

The tool works with the standard 5-field POSIX cron format used by Unix cron, GitHub Actions, and most job schedulers. 6-field expressions (with seconds) used by Spring/Quartz schedulers are not currently supported.

Why do the next execution times show in my local timezone?

The next execution calculator uses your browser's local system clock and timezone. Cron on a server runs in the server's timezone, which may differ. Make sure your server timezone matches your expected schedule.

Are the preset expressions safe to use in production?

Yes. The presets are standard, well-known cron expressions. Always verify the next execution times match your expectations before deploying, especially for month-end or year-end schedules.

Is there a cron expression for the last day of the month?

Standard 5-field cron cannot express 'last day of month' directly since months have different lengths. Some extended cron implementations support 'L' for last day. In standard cron, you would use day 28 for a safe cross-month schedule, or a combination with shell logic.

Can I use this tool offline?

Once the page is loaded, all cron parsing and execution calculation runs in JavaScript with no network requests. It works entirely offline.