Model: Task

Trigger: On Update

Trigger Fields: Stage (Task)

Before Update Domain: Stage is not = "Done"

Apply on: Stage= "Done"

I want to clone the (Done) task and add 28 days (4weeks) to the due date

I've tried to do it using Action To Do : Create a new record and i've done the cloning part but didn't figure out how to change the due date part (record.date_deadline).

I've tried to use

record.date_deadline=record.date_deadline+relativedelta(days=28)

 in the Value but it didn't work.