Cron Expression — Syntax, Format & Examples

A cron expression is a string of five fields separated by spaces — minute hour day-of-month month day-of-week — that defines when a scheduled job should run. Each field accepts numbers, wildcards (*), ranges (1-5), lists (1,3,5), and steps (*/5).

For example, the cron expression 0 */2 * * * means "at minute 0 past every 2nd hour" — so the job runs at midnight, 2 AM, 4 AM, 6 AM, and so on. The expression 0 9 * * 1-5 means "at 9:00 AM, Monday through Friday." These compact strings replace verbose scheduling configuration with a universal, portable format understood by Linux crontab, cloud platforms, CI/CD systems, and application frameworks.

Some systems extend the standard 5-field format: Quartz Scheduler (Java) adds a seconds field at the beginning, and AWS EventBridge adds a year field at the end. SimpleCronTab supports all major formats and lets you build, validate, and test cron expressions visually before deploying them.