Cron Expression Builder

How cron expressions schedule automation

A cron expression is five fields, minute, hour, day-of-month, month and day-of-week, that together describe when a job runs. It powers Linux crontabs, Kubernetes CronJobs, CI schedules and countless backup and cleanup tasks. The syntax is terse and easy to get wrong, which is why a job that was meant to run nightly ends up firing every minute. Building the expression visually and reading back a plain-English description removes most of that risk before the schedule reaches production.

Build and verify schedules safely

This builder lets you compose each field and immediately see the human-readable meaning and the next run times, all in your browser. That preview is the fastest way to catch a mistake such as confusing the day-of-month and day-of-week fields, or using a step value where you meant a range. Copy the finished expression straight into a crontab, a Kubernetes CronJob spec or a scheduled CI pipeline.

Common cron mistakes and how to fix them

The most frequent bug is a job that runs far more often than intended because a field was left as an asterisk. Another is timezone confusion: system cron uses the server timezone, while Kubernetes CronJobs default to UTC unless you set one. Always confirm the timezone your scheduler uses before trusting the times. To schedule builds and deploys the same way in a pipeline, see our GitHub Actions CI/CD deploy guide.

Frequently asked questions

What does five asterisks mean?

Every minute of every hour of every day. It is the most common accidental over-scheduling mistake.

What timezone does cron use?

Traditional cron uses the server local time; Kubernetes CronJobs default to UTC unless a timeZone is set.

How do I run a job every 15 minutes?

Use a step value in the minute field, such as the pattern that expands to 0,15,30,45.

Whats the difference between day-of-month and day-of-week?

They are separate fields; if both are set, most cron implementations run when either matches.