The following article refers to functionality available in Workflow builder, which can be accessed in one of the following locations, depending on your configuration:

Administration > HR > Workflows 
or
Administration > HR > Workflows > Workflows

Within Workflow Builder it is now possible to determine whether the workflow will trigger for employees who are currently in probation.  When building a workflow, you will see the following option: 

This setting will determine whether or not a workflow will trigger against an employee based on their probation date in the system. The probation date for an employee is set on their file in:

People > Employees 

On the employee's card click on the Change icon under the Core Details Heading:

And locate the Probationary date setting:

If you have set "Trigger against employees in probation" to "No" in your workflow, and if this probationary date is the future, the system will class the employee as being in probation and will not trigger the workflow against them.   

If the probationary date is in the past, the workflow will trigger against them.