Cron Expression Builder
Build cron job schedules visually without memorizing syntax. Set the fields, see the generated expression, and verify the next 5 run times — no guessing.
Frequently Asked Questions
What does the asterisk (*) mean in a cron expression?
An asterisk means "every" for that field. So * in the minute field means every minute; * in the hour field means every hour. The expression * * * * * runs every minute of every day. When you see */5 in the minute field, the slash means "every Nth" — so */5 means every 5 minutes. Most cron jobs combine specific values in some fields with asterisks in others: 0 9 * * 1 means at 9:00 AM every Monday specifically.
What is the difference between Day of Month and Day of Week?
These are two separate ways to target specific days. Day of Month (field 3) runs on a calendar date — 1 means the 1st of every month, 15 means the 15th. Day of Week (field 5) runs on a specific day name — 1 means Monday, 5 means Friday, 0 means Sunday. When both are set to specific values (not *), most systems run the job if either condition is true. To run only on the 1st Monday of the month, you need a more complex expression or a different scheduler like AWS EventBridge.
How do I run a cron job every 15 minutes between 9 AM and 5 PM?
Use the expression */15 9-17 * * *. The */15 in the minute field triggers every 15 minutes, and 9-17 in the hour field restricts it to the 9 AM through 5 PM window. This runs at 9:00, 9:15, 9:30, 9:45, 10:00 ... 17:45. Note that it will also fire at 17:00, 17:15, 17:30, and 17:45. If you only want it to run until 5:00 PM exactly, use 9-16 for the hours and add 0 */1 in a separate rule — or adjust your application logic to ignore runs after business hours.