CRON Parser

What is a Cron Expression

Cron is a time expression format used in Unix/Linux systems to define scheduled tasks. By combining 5 fields, you can precisely describe execution schedules — from every minute to specific dates each year. Modern cloud platforms (AWS CloudWatch, GitHub Actions, Kubernetes CronJob) all use similar syntax.

Field Format

┌──── Minute 0-59
│ ┌── Hour 0-23
│ │ ┌─ Day 1-31
│ │ │ ┌ Month 1-12
│ │ │ │ ┌ Weekday 0-7 (0 and 7 are both Sunday)
* * * * *

Special Characters

* any value · , multiple values (1,15) · - range (9-17) · / step (*/5)

Common Examples

Expression	Meaning
0 * * * *	Every hour on the hour
0 0 * * *	Daily at midnight
*/15 * * * *	Every 15 minutes
0 9 * * 1-5	Weekdays at 9:00 AM
0 2 * * 0	Every Sunday at 2:00 AM
30 4 1 * *	1st of every month at 4:30 AM

Note: Spring CRON uses 6 fields (adds "seconds" at the front), and Quartz uses 7 fields (adds "year" at the end) — both differ from the standard 5-field format.

Common Use Cases

• CI/CD pipelines: Schedule GitHub Actions or GitLab CI builds and deployments
• Database maintenance: Automate backups, data cleanup, and index rebuilding
• Monitoring & alerting: Configure periodic health checks, log rotation, and report generation
• Business scheduling: Timed email sends, report generation, and third-party data syncing

How to Use

1. Enter or paste a Cron expression in the input field (supports standard 5-field and 6-field Spring format)
2. The tool instantly parses and displays a human-readable description (e.g., "Every weekday at 9:00 AM")
3. Review the list of upcoming execution times to verify the schedule matches your expectations

FAQ

What's the difference between */5 and 0,5,10,...?

They are functionally equivalent — */5 is syntactic sugar for step values. However, some older cron implementations don't support the / syntax, requiring you to list all values explicitly.

How do I express "last day of the month"?

Standard 5-field Cron doesn't support "last day" semantics. Workarounds include using 28-31 with an in-script date check, or using extended formats that support the L symbol (e.g., Quartz's 0 0 L * ?).

Why isn't my Cron job running as expected?

Common causes: server timezone mismatch (check the TZ environment variable), syntax errors in the crontab file (missing trailing newline), script paths not using absolute paths, or task output not redirected causing mail queue buildup.