How to use this cron generator
- Pick a schedule from the "Common schedules" menu to fill the fields automatically, or set each field yourself.
- Edit the five fields, minute, hour, day of month, month and day of week, to fine tune the timing.
- Copy the cron string, read the explanation and check the next five run times, they update instantly as you type.
Nothing is submitted or stored: your schedule never leaves your device, so you can experiment freely.
How cron expressions work
A cron expression is five fields separated by spaces, written in the orderminute hour day-of-month month day-of-week. Each field accepts the same kinds of value, and a job runs whenever the current time matches every field at once. The fields and their ranges are:
- Minute, 0 to 59.
- Hour, 0 to 23.
- Day of month, 1 to 31.
- Month, 1 to 12.
- Day of week, 0 to 6, where 0 is Sunday.
You can write each field in a few ways, and they combine to cover most schedules:
- Every value, a star
*matches every value of the field. - Ranges,
1-5matches every value from 1 to 5 inclusive. - Lists,
1,3,5matches each listed value. - Steps,
*/15matches every 15th value starting from 0, so 0, 15, 30 and 45.
Day of month and day of week are joined with OR in standard cron: if both are set to something other than a star, the job runs when either one matches. Keeping one of them as a star avoids surprises.
Frequently asked questions
What is a cron expression?
A cron expression is a short string of five fields that tells a scheduler when to run a job. The fields are minute, hour, day of month, month and day of week, so "0 9 * * 1" means 9am every Monday.
What does an asterisk mean?
An asterisk matches every value of that field. The expression "* * * * *" runs once every minute because all five fields match everything.
How do steps like */15 work?
A step value such as */15 in the minute field means every 15 minutes (0, 15, 30 and 45). The number after the slash sets the interval.
Why are day of month and day of week treated as OR?
Standard cron runs the job when either the day of month or the day of week matches, as long as both are set. Leave one as a star to avoid unexpected extra runs.
Is my schedule uploaded?
No, the cron string, explanation and next run times are all calculated on your device and nothing is sent anywhere.