Cron Expression

The scheduler uses a UNIX cron expression to determine the frequency with which a scheduled task triggers an action on a job. You can use the UI to define a simple expression or you can define your own advanced expression using the cron expression syntax. The time zone specified for the scheduled task applies to the expression.

A cron expression is a string comprised of five or six fields separated by white space that represents a schedule. For example, the following cron expression triggers on the first day of every month at 9 AM:

0 9 1 1/1 ? *

Tip: If you create multiple scheduled tasks that run on a minute basis, configure those tasks to start at different minutes after the hour to avoid a sudden spike in triggered scheduled tasks.

The scheduler provides a UI where you can easily define the schedule without writing a cron expression. The scheduler generates the valid cron expression based on your selections. For example, the following image displays a selected schedule that triggers on the first day of every month at 9 AM in the US/Central time zone. The scheduler lists the read-only generated cron expression beneath the selected schedule:

Read-only generated cron expression listed beneath the selected schedule

Click Advanced to define your own cron expression. The fields in the cron expression can contain any of the following allowed values:


Field Name	Mandatory	Allowed Values
Minutes	yes	0-59
Hours	yes	0-23
Day of month	yes	1-31
Month	yes	1-12 or JAN-DEC
Day of week	yes	1-7 or SUN-SAT
Year	no	empty, 1970-2099

The fields can also contain various combinations of the allowed special characters for that field. For example, the asterisk (*) special character can be used in all fields to represent all values within the field.

For a list of the allowed special characters in each field and for example expressions, see the Quartz Scheduler documentation. Note that the Control Hub scheduler does not support the seconds field.