Cron Expression Explainer
Type or generate a standard 5-field cron expression to translate it into plain English. Inspect the next scheduled run times in your local timezone instantly. Every calculation runs locally in your browser.
This tool supports standard 5-field cron expressions used by crontab and Kubernetes CronJob. Quartz-style 6 and 7-field expressions (with seconds or year fields) are not supported.
Cron Expression
Description
Every 5 minutes
Next 5 Run Times
GitHub Actions schedules always run in UTC, and a Kubernetes CronJob uses the controller manager's time zone unless spec.timeZone is set.
Calculating upcoming runs...
Field Reference
Understanding Cron Expressions in DevOps
A cron expression is a string consisting of five fields separated by white space that represents a set of times to execute a routine. It is deeply ingrained in Unix-like operating systems via the crontab utility, and heavily relied upon in modern infrastructure, including Kubernetes CronJobs, GitHub Actions, and various CI/CD task schedulers.
Worked Example
Consider the expression 0 */6 * * *. It executes at minute 0 past every 6th hour. This means a job runs at the top of every sixth hour - midnight, 6 AM, noon, and 6 PM. Using step values like */5 (every 5) or lists like 1,15 (first and fifteenth) gives operators immense flexibility.
Common Day-of-Week Pitfall
A very common mistake involves confusing day-of-week numbering. While POSIX strictly specifies 0 through 6 for day-of-week, most cron implementations (such as Vixie cron, cronie, and Kubernetes) accept 7 as Sunday as well. Additionally, if both day-of-month and day-of-week are restricted (neither begins with an asterisk), the scheduler uses an OR condition - the job will run if either condition matches.
Standard POSIX Cron vs Quartz and Spring
The standard 5-field cron syntax is the foundation of Linux crontab and Kubernetes CronJobs. Schedulers like Quartz and Spring's @Scheduled use a 6-field variant with seconds at the front, while systems like Jenkins use a 5-field format extended with an H (hash) symbol for load balancing. This tool focuses strictly on the standard 5-field layout commonly encountered in server automation and DevOps interviews.