Cron Expression Builder

What is a cron expression?

A cron expression is a string of 5 fields defining when a scheduled job runs: minute (0-59), hour (0-23), day-of-month (1-31), month (1-12), day-of-week (0-6). Each field accepts: * (any), specific values (5), ranges (1-5), step values (*/15), and comma lists (1,3,5). The cron daemon checks every minute whether the current time matches the expression.

What does */ mean in a cron expression?

The */n step syntax means 'every n units.' */5 in the minute field means every 5 minutes (0, 5, 10, 15...). */2 in the hour field means every 2 hours (0, 2, 4, 6...). Example: */15 * * * * runs every 15 minutes. */1 is equivalent to * (every unit).

What are the most common cron patterns?

Every minute: * * * * *. Every 5 minutes: */5 * * * *. Every hour: 0 * * * *. Daily midnight: 0 0 * * *. Daily 9am: 0 9 * * *. Every weekday 8am: 0 8 * * 1-5. Every Monday: 0 9 * * 1. First of month: 0 0 1 * *. Every Sunday 2am: 0 2 * * 0.

What is the difference between day-of-month and day-of-week?

Day-of-month (field 3) specifies which calendar date (1-31). Day-of-week (field 5) specifies which weekday (0=Sunday, 1=Monday, ..., 6=Saturday). When both fields are set (not *), most cron implementations run the job when EITHER condition matches (OR logic). Use only one of the two for predictable scheduling.

How do I run a cron job in a specific timezone?

Standard cron expressions use the system's local timezone. To run at 9am IST (UTC+5:30), set to 3:30 UTC: 30 3 * * *. Modern schedulers like Kubernetes CronJobs, AWS EventBridge, and GitHub Actions allow setting CRON_TZ or a timezone config field separately from the expression.

What are @daily, @weekly, and @hourly special strings?

@reboot: run once at startup. @hourly = 0 * * * *. @daily = 0 0 * * *. @weekly = 0 0 * * 0. @monthly = 0 0 1 * *. @yearly = 0 0 1 1 *. These are convenience aliases supported by most modern cron daemons. Standard 5-field expressions are universally compatible across all schedulers.