This is a great question!

You can change the due date, but not the “done date” of a task. The Done date is stamped when the status changes of the task is moved to “Done”. 

There is a way to overwrite it, but you’d have to use the API and Postman (or another API platform tool). You can update a task’s completedAt date. See the documentation here: https://api.guidecx.com/api/v2/docs#patch-/tasks/-id-

If you see this happening a lot, then it may be more of a question about reminding your team to mark tasks as done when they complete them.