Cron Expression Builder
Build and decode cron schedule expressions visually.
Format: minute hour day-of-month month day-of-week (e.g., 0 9 * * 1-5 = 9 AM on weekdays)
What Is a Cron Expression?
A cron expression is a string of five fields that defines a recurring schedule. Used by Unix cron, Kubernetes CronJobs, CI/CD pipelines, and task schedulers worldwide, cron expressions control when automated jobs run. The five fields represent: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-6, where 0 = Sunday). An asterisk (*) means "every value," making * * * * * the simplest expression: run every minute.
Cron Syntax Cheat Sheet
Beyond simple values and asterisks, cron supports ranges (1-5 for Monday through Friday), lists (1,15 for the 1st and 15th), and step values (*/5 for every 5 minutes). You can combine these: 0 9-17 * * 1-5 means "on the hour, from 9 AM to 5 PM, Monday through Friday." Some implementations also support @reboot, @daily, @weekly, and other shorthand strings, though the five-field format is universal.
Common Pitfalls
The most common mistake is confusing day-of-month and day-of-week — setting both creates an OR condition (runs when either matches), not an AND condition. Another frequent error: 0 0 31 * * doesn't run on the last day of every month — it only runs in months that have 31 days. Timezone handling varies by implementation: some systems use UTC, others use the server's local time. Always verify which timezone your scheduler uses. This tool shows the next scheduled runs so you can confirm your expression works as intended before deploying.
When to Use This Tool
Use this builder to create cron expressions for scheduled backups, log rotation, report generation, deployment pipelines, monitoring checks, database maintenance, and any other recurring task. The human-readable description and next-run preview help you verify correctness before copying the expression into your crontab or configuration file.