webutilkit

Cron Expression Explainer

Break a 5-field cron expression down into plain English, field by field, in your browser.

How it works

A cron expression has five space-separated fields — minute, hour, day of month, month, and day of week — each describing when a job runs. Each field is parsed independently and explained in plain language, whether it is a wildcard, a single value, a range, a list, or a step interval.

The day-of-month and day-of-week quirk

When both the day-of-month and day-of-week fields are restricted at the same time, most cron implementations run the job whenever either one matches — an OR, not an AND. A schedule of 0 0 1 * 1 runs on the first of every month and every Monday, not only on Mondays that happen to fall on the first.

What this does not do

This explains a schedule’s meaning; it does not calculate upcoming run times, since that also depends on the timezone and cron implementation actually running the job.

Frequently asked questions

Which cron syntax is supported?

The standard 5-field format (minute, hour, day-of-month, month, day-of-week), including *, single values, ranges (1-5), lists (1,3,5), and step values (*/15).

What happens when both day-of-month and day-of-week are set?

This tool explains each field independently. In most cron implementations, setting both means the job runs when either condition is met, not only when both are — a common source of surprise.