Question 1

What is a cron expression?

Accepted Answer

A cron expression is a string of five fields separated by spaces that defines when a scheduled job should run. The fields represent minute, hour, day of month, month, and day of week. An asterisk (*) means every value for that field.

Question 2

What does the asterisk (*) mean in a cron expression?

Accepted Answer

An asterisk means every possible value for that field. For example, * in the hour field means every hour. * in the minute field means every minute.

Question 3

What is the difference between day of month and day of week?

Accepted Answer

Day of month selects a specific calendar date (1 to 31). Day of week selects a day by name or number (0 = Sunday, 6 = Saturday). Most cron implementations run a job if either field matches, so combining both can cause unexpected double-triggering.

Question 4

How accurate are the next run time predictions?

Accepted Answer

The next run times are calculated from the current moment using the expression fields you have set. They are computed entirely in your browser and are as accurate as your local system clock.

Question 5

Can I use this expression with any scheduler?

Accepted Answer

The standard five-field format shown here is supported by UNIX cron, crontab, AWS EventBridge, GitHub Actions, and most job schedulers. Some systems (like Quartz) add a seconds field as the first field, which is not included here.

Cron Builder

Three steps to done

When to use this

Schedule backups

GitHub Actions

AWS EventBridge

Free visual cron expression builder

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