Finding a Date variance from 2 tables

[PowerBIAllStars]

Hi I am trying to find a date difference for milestones reporting over a number of periods. Variance has to be negative if slipped bewtween the periods. The dates are indifferent tables, the row has a common Milestone ID. I have a linked the tables as below to a DAte Table so I can somehow catergorise Year/Month etc. When I try to use DateDiff I add New Column to the Table and try but I get the below error message:

Below is a extract of the model view.

Please help! 

[PowerBIAllStars]

Data Table as below, its much larger, what I would like to do is link the Forecast date per period to the "YearPeriod" data so I can filter on a particular "YearPeriod". I have linked the Baseline table to the date Table so I can show the baseline "YearPeriod", but how can I show the Forecast "YearPeriod" to multiple different coumns? 

Thank you. 

Date	DateSK	Period	ShortFinYearNum	YearPeriod	YearNum
23/06/2024	20240623	4	2425	2425_P4	2024
24/06/2024	20240624	4	2425	2425_P4	2024
25/06/2024	20240625	4	2425	2425_P4	2024
26/06/2024	20240626	4	2425	2425_P4	2024
27/06/2024	20240627	4	2425	2425_P4	2024
28/06/2024	20240628	4	2425	2425_P4	2024
29/06/2024	20240629	4	2425	2425_P4	2024
30/06/2024	20240630	4	2425	2425_P4	2024
01/07/2024	20240701	4	2425	2425_P4	2024
02/07/2024	20240702	4	2425	2425_P4	2024
03/07/2024	20240703	4	2425	2425_P4	2024
04/07/2024	20240704	4	2425	2425_P4	2024
05/07/2024	20240705	4	2425	2425_P4	2024
06/07/2024	20240706	4	2425	2425_P4	2024
07/07/2024	20240707	4	2425	2425_P4	2024

[PowerBIAllStars]

Period 3 data

ID	Milestone Des	MS Tier	23-24 P03
101	MS101	1	04/08/2024
102	MS102	2	12/08/2024
103	MS103	3	16/08/2024
104	MS104	1	15/08/2024
105	MS105	2	29/08/2024
106	MS106	3	14/09/2024
107	MS107	1	02/08/2025
108	MS108	2	11/08/2025
109	MS109	3	12/08/2025
110	MS110	1	13/08/2025
111	MS111	2	15/08/2025
112	MS112	3	12/09/2025

[PowerBIAllStars]

Baseline Data (at the begining of the project:

ID	Milestone Des	MS Tier	BL	PM	Status
101	MS101	1	12/07/2024	Jiya	Complete
102	MS102	2	26/07/2024	Jiya	Complete
103	MS103	3	29/07/2024	Jiya	In Progress
104	MS104	1	01/08/2024	Harry	In Progress
105	MS105	2	15/08/2024	John	In Progress
106	MS106	3	28/08/2024	Jiya	In Progress
107	MS107	1	15/07/2025	Harry	In Progress
108	MS108	2	29/07/2025	John	Not Started
109	MS109	3	01/08/2025	John	Not Started
110	MS110	1	04/08/2025	Jiya	Not Started
111	MS111	2	18/08/2025	Harry	Not Started
112	MS112	3	31/08/2025	Harry	Not Started

Period 2 data

ID	Milestone Des	MS Tier	23-24 P02
101	MS101	1	09/08/2024
102	MS102	2	16/08/2024
103	MS103	3	19/08/2024
104	MS104	1	20/08/2024
105	MS105	2	30/08/2024
106	MS106	3	19/09/2024
107	MS107	1	12/08/2025
108	MS108	2	19/08/2025
109	MS109	3	22/08/2025
110	MS110	1	23/08/2025
111	MS111	2	02/09/2025
112	MS112	3	22/09/2025

[lbendlin]

You'll have to work on your data model.  Do not join fact tables like this.  (Rather append them).

Please provide sample data (with sensitive information removed) that covers your issue or question completely, in a usable format (not as a screenshot). Leave out anything not related to the issue.
https://community.fabric.microsoft.com/t5/Community-Blog/How-to-provide-sample-data-in-the-Power-BI-...
Please show the expected outcome based on the sample data you provided.

https://community.fabric.microsoft.com/t5/Desktop/How-to-Get-Your-Question-Answered-Quickly/m-p/1447...