โ Frequently Asked Questions โ Cron Parser
What is a cron expression?
A cron expression is a string of 5 fields (minute, hour, day-of-month, month, day-of-week) that defines a schedule for automated tasks. For example, "0 9 * * 1-5" means "at 9:00 AM, Monday through Friday". Cron jobs are widely used in Linux systems, CI/CD pipelines, cloud schedulers, and backend services.
What is the difference between 5-field and 6-field cron?
Standard Unix cron uses 5 fields (minute through day-of-week). Some implementations like Quartz Scheduler and AWS EventBridge use 6 fields by adding a seconds field at the start, or a year field at the end. This tool uses the standard 5-field format used by Linux crontab, GitHub Actions, and most job schedulers.
Why are my next run times different from what I expected?
Cron times are always interpreted in the server's local timezone. If your server is in UTC and you expect 9 AM IST, you need to account for the +5:30 offset (use 3:30 AM UTC = "30 3 * * *"). Always check your deployment environment's timezone configuration when setting up cron jobs.
Can I schedule a cron to run every 30 seconds?
Standard 5-field cron cannot schedule sub-minute intervals โ the minimum unit is 1 minute. To run every 30 seconds, you'd need two cron entries running the same task with an offset, or use a tool that supports seconds in the schedule (like Quartz with 6-field cron). For sub-minute tasks, consider application-level scheduling instead.