Find the difference between two dates from two different tables
I am looking to find the difference between two dates from two different tables. The tables being used are Assignments and AssigmentBaselines. The columns used are 'Assignments[AssignmentActualFinishDate] and 'AssignmentBaselines'[AssignmentBAselineFinishDate]. The tables have a relationship many to one (*:1) and has a both cross filter direction.
The formula I have been using is:
Baseline Days +/- = DATEDIFF(AssignmentBaselines[AssignmentBaselineFinishDate], RELATED(Assignments[AssignmentActualFinishDate].[Day]))
The error I keep getting is "Too few arguments were passed to the DATEDIFF function. The minimum argument count for the function is 3."
I have looked through many different forum post and I have tried many different ways to solve this issue but I keep coming up short. Any help would be appreciated.