Need to use date functions in Approval workflow

Summary:

Use date functions in the Approval workflow for the 'Manage personal contribution' task.

Content (required):

My requirement is to create a rule in the approval workflow to check if the Compensation Start Date is the first of any month.

(TRUNC(Worker's Other Compensation Details.Other Compensation Start Date.toGregorianCalendar(),'MM') = '01')

I have tried using the above function but it does not work. Please suggest a way to achieve this requirement.

Version (include the version you are using, if applicable):

23A

Code Snippet (add any code snippets that support your topic, if applicable):