In this article
What Is a Cron Expression?
A cron expression is a string that defines a schedule for recurring tasks. Originally from Unix systems, cron syntax is now used in cloud schedulers (AWS EventBridge, GCP Cloud Scheduler), CI/CD systems (GitHub Actions, Jenkins), and application frameworks to define when jobs should run automatically.
A standard cron expression has 5 fields: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-6). Extended formats add a seconds field at the beginning or a year field at the end.
How Cron Parsing Works
CheckTown's cron parser decodes the expression and shows you exactly when it will trigger.
- Field parsing — breaks down each field and validates the range and special characters
- Human description — converts the expression to plain English (e.g., 0 9 * * 1 → Every Monday at 9:00 AM)
- Next execution times — shows the next 5-10 scheduled run times based on the expression
Try it free — no signup required
Parse a Cron Expression →When To Use the Cron Parser
The cron parser is useful whenever you need to create, read, or debug scheduled task configurations.
- Scheduled jobs — verify cron expressions for database backups, report generation, or cleanup tasks
- Cloud scheduling — validate EventBridge or Cloud Scheduler cron rules before deploying
- On-call schedules — confirm that monitoring alerts or maintenance windows are scheduled correctly
Frequently Asked Questions
What does * mean in cron?
An asterisk (*) means 'every valid value' for that field. So * in the minute field means 'every minute', * in the hour field means 'every hour', etc. The expression * * * * * means 'run every minute of every hour of every day'.
What is the difference between 5-field and 6-field cron?
Traditional Unix cron uses 5 fields (minute, hour, DOM, month, DOW). Many modern systems add a 6th field for seconds at the start, producing (second, minute, hour, DOM, month, DOW). AWS and GCP use 6-field expressions. Always check which format your scheduler expects.
Can I use both day-of-month and day-of-week in the same expression?
In most cron implementations, using specific values in both DOM and DOW creates an OR condition — the job runs if either condition is met. This behavior is confusing and often unintentional. If you need a job to run on a specific weekday of a specific date, use a more specific expression or conditional logic in the job itself.