Cron Expression Explainer
Parse any cron expression into a human-readable schedule and preview upcoming run times.
About this tool
A cron expression is five whitespace-separated fields that tell a scheduler (cron, Kubernetes, AWS EventBridge, GitHub Actions) when a job should run. The fields are, in order: minute, hour, day-of-month, month, day-of-week. Reading them aloud is easy once you know the order; writing them by hand is error-prone, which is why an explainer is useful.
Common patterns: */5 * * * * means every 5 minutes; 0 9 * * 1-5 means 09:00 Monday through Friday; 0 0 1 * * means midnight on the first day of every month; 30 3 * * * means 03:30 every day.
Type or paste an expression and the tool translates it into plain English and lists the next several execution times so you can confirm the schedule behaves the way you expect before deploying it. It supports the standard 5-field Vixie-cron syntax including ranges, lists, step values (*/N), and named days.
FAQ
What is the sixth field some crontabs have? ›
Traditional Unix crontab entries have a leading field for the user the job runs as, plus the five scheduling fields. Quartz and Spring add a trailing seconds field, and some schedulers add a year or day-of-week with an L/W modifier. This tool covers the standard five-field syntax used by Kubernetes, GitHub Actions, and AWS EventBridge.
How is */5 different from 0,5,10,15,20,25,30,35,40,45,50,55? ›
They are identical for minutes. The step syntax */5 is shorthand for the explicit list. Steps also work on other fields: */2 in the hour field means every other hour (0, 2, 4, …, 22).
What happens when day-of-month and day-of-week are both set? ›
In standard cron, a match on either field triggers the job — they are OR-ed, not AND-ed. So 0 0 13 * 5 runs at midnight on Friday the 13th and also every other Friday. Quartz uses AND semantics instead, which is a common source of surprise when migrating schedules.
Why does my schedule run in the wrong timezone? ›
Cron uses the server's system timezone by default. Kubernetes CronJobs and AWS EventBridge let you specify a timezone explicitly. Always confirm the timezone in production — a job that runs at 02:00 server time may run at a surprising local time in UTC.
What do the red and amber warning badges mean? ›
The tool checks your expression for impossible or surprising day/month combinations. A red badge means a day will never fire in the selected month(s) — for example '30 0 30 2 *' (Feb 30) or '0 0 31 4 *' (Apr 31). An amber badge means the day is skipped in some of the selected months, or only fires in leap years (Feb 29). These are warnings, not errors — the expression is still valid cron, it just may not do what you intended.
Can I share a cron expression with a coworker? ›
Yes. Click the Share button to copy a link that encodes the current expression in the URL (?c=...). Opening that link loads the expression and its explanation immediately, so you can paste it into a ticket, PR, or chat to discuss a schedule before deploying it.