When do day-of-month and day-of-week combine?

When both fields are restricted, cron matches if either matches (OR). When only one is restricted, that one must match.

Why is there no result for 31 February?

If no instant matches within a year the tool reports an empty run list rather than looping forever.

Tool

Cron Expression Generator

Validate a five-field cron expression, describe it, and list its next run times.

Try it

This tool runs entirely in your browser. Nothing you type or paste is sent anywhere.

*/15 9-17 * * MON-FRI runs next at 2026-01-05T09:00:00.000Z.

How it works

Split the expression into the five standard fields.
Expanded ranges, lists, steps, and month/day names into value sets.
Scanned forward minute by minute (bounded to one year) for matching UTC instants.

Cron uses UTC and runs the day-of-month and day-of-week rules with OR semantics when both are restricted.

Usage

Enter a five-field cron expression (minute hour day-of-month month day-of-week).
Choose how many upcoming runs to list.
Read the description and the next run times.

Examples

Every 15 minutes on weekday business hours

{
  "expression": "*/15 9-17 * * MON-FRI",
  "count": 3,
  "reference": "2026-01-05T08:00:00.000Z"
}

First of each month at midnight

{
  "expression": "0 0 1 * *",
  "count": 2,
  "reference": "2026-01-15T00:00:00.000Z"
}

Limitations

Reading a cron field

A field is a comma list of items. Each item is a single value, a range (1-5), a step (*/15 or 1-30/5), or a wildcard. Month and day-of-week accept three-letter names.

Why UTC matters

Many schedulers interpret cron in the server's local time. This tool uses UTC explicitly so that the listed run times are unambiguous.

Frequently asked questions

When do day-of-month and day-of-week combine?: When both fields are restricted, cron matches if either matches (OR). When only one is restricted, that one must match.
Why is there no result for 31 February?: If no instant matches within a year the tool reports an empty run list rather than looping forever.

Sources

POSIX crontab specification — The Open Group