Cron Expression Parser
Cron expressions are used in Unix-like systems and many scheduling tools (cron, systemd timers, Kubernetes CronJobs, GitHub Actions) to define recurring schedules. Each expression consists of five fields: minute, hour, day of month, month, and day of week.
This tool parses any standard 5-field cron expression into a human-readable description and shows the next 5 scheduled run times. It supports wildcards (*), ranges (1-5), lists (1,3,5), and step values (*/15).
How it works
A cron expression has the format: minute (0-59) hour (0-23) day-of-month (1-31) month (1-12) day-of-week (0-6, where 0 = Sunday). Special characters: * (any), , (list), - (range), / (step).
Use cases
- Verifying cron schedules before deploying to production
- Understanding legacy cron expressions in existing systems
- Planning scheduled tasks for CI/CD pipelines
- Debugging timing issues in cron-based automation
Frequently asked questions
What do the 5 fields of a cron expression mean?
From left to right they are: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-6, where 0 = Sunday). Each field accepts a specific value, a wildcard (*), a range (1-5), a list (1,3,5), or a step value (*/15). Together the five fields define when the job runs.
What does */15 mean in a cron expression?
The / character defines a step value. In the minute field, */15 means "every 15 minutes" — the job fires at minutes 0, 15, 30, and 45 of each hour. The same syntax works in other fields, so */2 in the hour field means every 2 hours.
How do I schedule a cron job to run every day at midnight?
Use the expression 0 0 * * * — minute 0, hour 0, any day of month, any month, any day of week. For a different time, change the first two fields: 30 6 * * * runs daily at 06:30. This tool shows the next 5 run times so you can confirm the schedule before deploying.
In cron, is day-of-week 0 Sunday or Monday?
In standard cron, day-of-week runs from 0 to 6 with 0 = Sunday, so 1 is Monday and 6 is Saturday. Some implementations also accept 7 as an alias for Sunday, and many accept three-letter names like SUN or MON. This parser follows the standard 0 = Sunday convention.
Where are cron expressions used?
Cron expressions drive scheduled tasks in Unix-like systems (crontab), systemd timers, Kubernetes CronJobs, and CI/CD schedulers like GitHub Actions (the schedule trigger). All of these use the standard 5-field format that this parser decodes. Verifying an expression and previewing its next run times before deployment prevents jobs from firing at the wrong time in production.