Cron Expression: 5 Fields vs 6 Fields

The most confusing aspect of cron is that different systems use different numbers of fields. Standard Unix cron uses 5 fields: minute hour day-of-month month day-of-week. Quartz Scheduler uses 6-7 fields with seconds: second minute hour day-of-month month day-of-week [year]. AWS uses 6 fields with year: minute hour day-of-month month day-of-week year.

This matters because the same expression means different things in different systems. 0 15 10 * * ? in Quartz means "10:15:00 AM daily" (seconds=0, minutes=15, hours=10). But if you paste this into a standard crontab expecting 5 fields, it's invalid.

How to tell which format you need: count the fields your system expects. Standard cron (crontab, Vercel, GitHub Actions): 5 fields. Quartz (Java Spring): 6-7 fields, starts with seconds. AWS (EventBridge, CloudWatch): 6 fields, ends with year. When in doubt, check your platform's documentation. SimpleCronTab auto-detects the format based on field count and syntax.