TAT Calculation based on Next Group

Hi Sebas7,

You can create a calendar table (Calendar = CALENDAR("2017-9-1",TODAY())) and add a index column in Query Editor,then create calculated columns below in the fact table: 

WinStreak =
var LastLossIndex = CALCULATE( MAX('Table1'[Index]),
FILTER('Table1', 'Table1'[Group] <> EARLIER(Table1[Group])),
FILTER('Table1', [Index] <= EARLIER([Index]))
)

return
[Index] - LastLossIndex

NewGroup = CALCULATE(MAX(Table1[Index]),FILTER('Table1','Table1'[Index]<=EARLIER(Table1[Index]) && Table1[Group]=EARLIER(Table1[Group])&& Table1[WinStreak]=1&& Table1[Case]=EARLIER(Table1[Case])))

NewDate = DATEVALUE('Table1'[Date])

Diff = var MaxDate=CALCULATE(MAX('Table1'[NewDate]),FILTER('Table1','Table1'[Case]=EARLIER(Table1[Case])&&Table1[NewGroup]=EARLIER(Table1[NewGroup])))
var MinDate=CALCULATE(MIN('Table1'[NewDate]),FILTER('Table1','Table1'[Case]=EARLIER(Table1[Case])&&Table1[NewGroup]=EARLIER(Table1[NewGroup])))
return
IF(MinDate=MaxDate,0,DATEDIFF(LOOKUPVALUE('Calendar'[Date],'Calendar'[Date],MinDate),LOOKUPVALUE('Calendar'[Date],'Calendar'[Date],MaxDate),DAY)-CALCULATE(COUNTROWS('Calendar'),FILTER('Calendar',('Calendar'[Weekday]=6 || 'Calendar'[Weekday]=7)&&'Calendar'[Date]>=MinDate&&'Calendar'[Date]<=MaxDate))+1)

You can download attached pbix file to have a look. 

Best Regards,
Qiuyun Yu