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:

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.