Cron Explainer

A cron expression is five space-separated fields that describe a repeating schedule: <minute> <hour> <day-of-month> <month> <day-of-week>. Each field accepts a specific number, a wildcard (* means "every"), a range (1-5), a list (1,15), or a step (*/10 means "every 10"). The scheduler fires a job whenever all five fields simultaneously match the current time.

This tool parses your expression client-side and uses your browser's Intl.DateTimeFormat API to render the next five run times in your chosen IANA timezone. No data leaves your machine - useful when pasting expressions that include business-sensitive schedules. The human-readable description is generated by the cronstrue library, and the next-run computation uses cron-parser.

Common pitfall: day-of-week 0 and 7 both mean Sunday in standard cron, but implementations vary. If a job doesn't fire when you expect, double-check the day-of-week field against your platform's docs. AWS EventBridge, GitHub Actions, and traditional cron all accept the same five-field syntax, but some (like Quartz Scheduler) add a sixth field for seconds - this tool covers the standard five-field form only.