Hi hansreivers,
Okay well in that case see if the Custom ISO Week, column does the trick for you.
let
    Source = List.Dates(StartDate, Length, #duration(1, 0, 0, 0)),
    #"Converted to Table" = Table.FromList(Source, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    #"Renamed Columns" = Table.RenameColumns(#"Converted to Table",{{"Column1", "Date"}}),
    #"Changed Type" = Table.TransformColumnTypes(#"Renamed Columns",{{"Date", type date}}),
    StartDate = #date(#"Start year calendar",1, 1),
    EndDate = #date(#"End year calendar", 12, 31) ,
    Today = DateTime.Date(DateTime.LocalNow()),
    Length = Duration.Days(EndDate - StartDate) + 1,
    DayOfWeek = Date.DayOfWeek(Today)+1,
    StartWeekDate = Date.AddDays(Today, 1-DayOfWeek),
    DayOfMonth = Date.Day(Today),
    StartMonthDate = Date.AddDays(Today,1-DayOfMonth),
    EndQuarterDate = Date.EndOfQuarter(Today),
    
    #"Inserted Year" = Table.AddColumn(#"Changed Type" , "Year", each Date.Year([Date])),
    weekStart = Day.Monday,
    InsertWeekNumber = Table.AddColumn(#"Inserted Year", "Custom ISO Week", each
        if Number.RoundDown((Date.DayOfYear([Date])-(Date.DayOfWeek([Date], weekStart)+1)+10)/7)=0
        then Number.RoundDown((Date.DayOfYear(#date(Date.Year([Date])-1,12,31))-(Date.DayOfWeek(#date(Date.Year([Date])-1,12,31), weekStart)+1)+10)/7)
        else if (Number.RoundDown((Date.DayOfYear([Date])-(Date.DayOfWeek([Date], weekStart)+1)+10)/7)=53 and (Date.DayOfWeek(#date(Date.Year([Date]),12,31), weekStart)+1<4))
        then 1 else Number.RoundDown((Date.DayOfYear([Date])-(Date.DayOfWeek([Date], weekStart)+1)+10)/7), type number),
    InsertCurrWeekOffset = Table.AddColumn(InsertWeekNumber, "CurrWeekOffset", each (Number.From(Date.StartOfWeek([Date], weekStart))-Number.From(Date.StartOfWeek(Today, weekStart)))/7),
    GroupRows = Table.Group(InsertCurrWeekOffset, {"Year"}, 
        {
            {"data", each Table.RemoveLastN( Table.RemoveFirstN( _, 7), 7), type table [Date=nullable date, Year=number, Custom ISO Week=number, CurrWeekOffset=number]}, 
            {"top", each let t = Table.FirstN(_, 7), v = List.Max(List.RemoveMatchingItems(t[Custom ISO Week], {2})) in Table.ReplaceValue( t, v, 1, Replacer.ReplaceValue, {"Custom ISO Week"}), type table [Date=nullable date, Year=number, Custom ISO Week=number, CurrWeekOffset=number]}, 
            {"bottom", each let t = Table.LastN(_, 7), v = List.Max(List.RemoveMatchingItems(t[Custom ISO Week], {53})) in Table.ReplaceValue( t, each [Custom ISO Week], each if List.Contains( {1, 53}, [Custom ISO Week]) then v else [Custom ISO Week], Replacer.ReplaceValue, {"Custom ISO Week"}), type table [Date=nullable date, Year=number, Custom ISO Week=number, CurrWeekOffset=number]}
        }
    ),
    Transform = Table.TransformColumns( GroupRows, {{"top", each let v = List.Mode([Custom ISO Week]), m = List.Mode([CurrWeekOffset]) in Table.ReplaceValue(_, (x)=> x[CurrWeekOffset], (x)=> if x[Custom ISO Week] = v then m else x[CurrWeekOffset], Replacer.ReplaceValue, {"CurrWeekOffset"} ), type table [Date=nullable date, Year=number, Custom ISO Week=number, CurrWeekOffset=number] }, {"bottom", each let v = List.Mode([Custom ISO Week]), m = List.Mode([CurrWeekOffset]) in Table.ReplaceValue(_, (x)=> x[CurrWeekOffset], (x)=> if x[Custom ISO Week] = v then m else x[CurrWeekOffset], Replacer.ReplaceValue, {"CurrWeekOffset"} ), type table [Date=nullable date, Year=number, Custom ISO Week=number, CurrWeekOffset=number] }}),
    UpdatedWeeks = Table.Combine( Table.AddColumn(Transform, "temp", each [top] & [data] & [bottom], type table [Date=nullable date, Year=number, Custom ISO Week=number, CurrWeekOffset=number])[temp] ),
    #"Inserted Month" = Table.AddColumn(UpdatedWeeks, "Month", each Date.Month([Date])),
    #"Inserted Quarter" = Table.AddColumn(#"Inserted Month", "Quarter", each Date.QuarterOfYear([Date])),
    #"Inserted Day" = Table.AddColumn(#"Inserted Quarter", "Day", each Date.Day([Date])),
    #"Inserted Quarter Name" = Table.AddColumn(#"Inserted Day", "Quarter Name", each Text.Combine({"Q",Number.ToText([Quarter])})),
    #"Inserted YYYYQ" = Table.AddColumn(#"Inserted Quarter Name", "YYYYQ", each [Year] * 10 + [Quarter]),
    #"Inserted Quarter End Date" = Table.AddColumn(#"Inserted YYYYQ", "Quarter Date End", each Date.EndOfQuarter([Date])),
    #"Inserted Quarter Start Date" = Table.AddColumn(#"Inserted Quarter End Date", "Quarter Date Start", each Date.AddDays(Date.EndOfMonth(Date.AddQuarters([Quarter Date End],-1)),1)),
    #"Inserted Month Name" = Table.AddColumn(#"Inserted Quarter Start Date", "Month Name", each Date.MonthName([Date], "en-US"), type text),
    #"Inserted Month Name NL" = Table.AddColumn(#"Inserted Month Name", "Month Name NL", each Date.MonthName([Date], "nl-NL")),
    #"Inserted DateKey" = Table.AddColumn(#"Inserted Month Name NL", "DateKey", each [Year] * 10000 + [Month] * 100 + [Day]),
    #"Inserted Month Name Short" = Table.AddColumn(#"Inserted DateKey", "Month Name Short", each Text.Start([Month Name], 3), type text),
    #"Inserted Month Name Short NL" = Table.AddColumn(#"Inserted Month Name Short", "Month Name Short NL", each Date.ToText([Date], "MMM")),
    #"Inserted YYYYMM" = Table.AddColumn(#"Inserted Month Name Short NL", "YYYYMM", each [Year]*100 + [#"Month"]),
    #"Inserted MMM-YYYY" = Table.AddColumn(#"Inserted YYYYMM", "MMM-YYYY", each Text.Combine({[Month Name Short], "-", Number.ToText([Year])})),
    #"Inserted MMM-YYYY NL" = Table.AddColumn(#"Inserted MMM-YYYY", "MMM-YYYY NL", each Text.Combine({[Month Name Short NL], "-", Number.ToText([Year])})),
    #"Inserted Month Start Date" = Table.AddColumn(#"Inserted MMM-YYYY NL", "Month Date Start", each Date.AddDays([Date], 1-[Day])),
    #"Inserted Month End Date" = Table.AddColumn(#"Inserted Month Start Date", "Month Date End", each Date.EndOfMonth([Month Date Start])),
    #"Inserted Day of Week" = Table.AddColumn(#"Inserted Month End Date", "Day of Week", each Date.DayOfWeek([Date])+1, Int64.Type),
    #"Inserted Day Name" = Table.AddColumn(#"Inserted Day of Week", "Day Name", each Date.DayOfWeekName([Date], "en-US"), type text),
    #"Inserted Day Name NL" = Table.AddColumn(#"Inserted Day Name", "Day Name NL", each Date.DayOfWeekName([Date], "nl-NL")),
    #"Inserted Day Name Short" = Table.AddColumn(#"Inserted Day Name NL", "Day Name Short", each Text.Start([Day Name], 3), type text),
    #"Inserted Day Name Short NL" = Table.AddColumn(#"Inserted Day Name Short", "Day Name Short NL", each Text.Start([Day Name NL], 2)),
    #"Inserted ISO Date" = Table.AddColumn(#"Inserted Day Name Short NL", "getISODate", each getISO8601Week([Date])),
    #"Inserted ISO Year" = Table.AddColumn(#"Inserted ISO Date", "ISO Year", each Text.Start([getISODate], 4)),
    #"Inserted ISO Week" = Table.AddColumn(#"Inserted ISO Year", "ISO Week", each Text.Middle([getISODate], 6, 2)),
    #"Inserted ISO Week Name" = Table.AddColumn(#"Inserted ISO Week", "ISO Week Name", each Text.Middle([getISODate], 5, 3)),
    #"Inserted YYYWW" = Table.AddColumn(#"Inserted ISO Week Name", "YYYYWW", each Number.From([ISO Year]) * 100 + Number.From([ISO Week])),
    InsertCustomYYYWW = Table.AddColumn(#"Inserted YYYWW", "MDK YYYYWW", each [Year] * 100 + [Custom ISO Week], Int64.Type),
    #"Inserted Week Start Date" = Table.AddColumn(InsertCustomYYYWW, "Week Date Start", each Date.AddDays([Date], 1-[Day of Week])),
    #"Inserted Week End Date" = Table.AddColumn(#"Inserted Week Start Date", "Week Date End", each Date.AddDays([Week Date Start], 6)),
    #"Inserted Day Index" = Table.AddColumn(#"Inserted Week End Date", "Day Index", each Duration.Days(Duration.From([Date] - Today))),
    #"Inserted Week Index" = Table.AddColumn(#"Inserted Day Index", "Week Index", each Duration.Days(Duration.From(StartWeekDate - [Week Date Start])) / -7),
    #"Inserted Month Index" = Table.AddColumn(#"Inserted Week Index", "Month Index", each Number.Round(Duration.Days(Duration.From(StartMonthDate - [Month Date Start])) / -30.4 , 0)),
    #"Inserted Quarter Index" = Table.AddColumn(#"Inserted Month Index", "Quarter Index", each Number.Round(Duration.Days(Duration.From(EndQuarterDate - [Quarter Date End])) / -91.25 , 0)),
    #"Inserted Year Index" = Table.AddColumn(#"Inserted Quarter Index", "Year Index", each [Year] - Date.Year(Today)),
    #"Inserted Current Week" = Table.AddColumn(#"Inserted Year Index", "Current Week", each if[Week Index] = 0 then "Current Week" else Text.Combine({[ISO Week Name], "-", Number.ToText([Year])})),
    #"Inserted Current Month" = Table.AddColumn(#"Inserted Current Week", "Current Month", each if [Month Index] = 0 then "Current Month" else [#"MMM-YYYY"]),
    #"Inserted Current Quarter" = Table.AddColumn(#"Inserted Current Month", "Current Quarter", each if [Quarter Index] = 0 then "Current Quarter" else Text.Combine({[Quarter Name], "-", Number.ToText([Year])})),
    #"Inserted Current Year" = Table.AddColumn(#"Inserted Current Quarter", "Current Year", each if [Year Index] = 0 then "Current Year" else Number.ToText([Year])),
    #"Inserted Day Type" = Table.AddColumn(#"Inserted Current Year", "Day Type", each if [Day of Week] <= 5 then "Weekdag" else "Weekend"),
    #"Insert YYYY-MM kolom" = Table.AddColumn(#"Inserted Day Type", "ISO YYYYWW", each Text.Combine({Text.Start(Text.From([YYYYMM], "nl-NL"), 4), "-", Text.Middle(Text.From([YYYYMM], "nl-NL"), 4)}), type text),
    ChType = Table.TransformColumnTypes(#"Insert YYYY-MM kolom",{{"Year", Int64.Type}, {"Custom ISO Week", Int64.Type}, {"CurrWeekOffset", Int64.Type}, {"Month", Int64.Type}, {"Quarter", Int64.Type}, {"Day", Int64.Type}, {"YYYYQ", Int64.Type}, {"DateKey", Int64.Type}, {"YYYYMM", Int64.Type}, {"Day of Week", Int64.Type}, {"ISO Year", Int64.Type}, {"ISO Week", Int64.Type}, {"YYYYWW", Int64.Type}, {"MDK YYYYWW", Int64.Type}, {"Day Index", Int64.Type}, {"Week Index", Int64.Type}, {"Month Index", Int64.Type}, {"Quarter Index", Int64.Type}, {"Year Index", Int64.Type}, {"Quarter Name", type text}, {"Month Name", type text}, {"Month Name NL", type text}, {"Month Name Short", type text}, {"Month Name Short NL", type text}, {"MMM-YYYY", type text}, {"MMM-YYYY NL", type text}, {"Day Name", type text}, {"Day Name NL", type text}, {"Day Name Short", type text}, {"Day Name Short NL", type text}, {"getISODate", type text}, {"ISO Week Name", type text}, {"Current Week", type text}, {"Current Month", type text}, {"Current Quarter", type text}, {"Current Year", type text}, {"Day Type", type text}, {"ISO YYYYWW", type text}, {"Quarter Date End", type date}, {"Quarter Date Start", type date}, {"Month Date Start", type date}, {"Month Date End", type date}, {"Week Date Start", type date}, {"Week Date End", type date}}),
    #"Added Custom" = Table.AddColumn(ChType, "Hulpkolom (eerst in DAX, daarna ""vertaald naar M"" in PQ", each if [Year]=[ISO Year] then [ISO Week] else
        if [Year]<=[ISO Year] and [ISO Week]=1 then [ISO Week]+52 else
        if [Year]>=[ISO Year] and [ISO Week]=52 then [ISO Week]-51
        else
        if [Year]>=[ISO Year] and [ISO Week]=53 then [ISO Week]-52
        else "KLOPT NIET"),
    #"Added Custom Column1" = Table.AddColumn(#"Added Custom", "Jaar(datum) + HRE ISO week", each Text.Combine({Text.PadEnd(Text.From([Year], "nl-NL"), 5, "-"), Text.PadStart(Text.From([#"Hulpkolom (eerst in DAX, daarna ""vertaald naar M"" in PQ"], "nl-NL"), 2, "0")}), type text),
    #"Changed Type1" = Table.TransformColumnTypes(#"Added Custom Column1",{{"Hulpkolom (eerst in DAX, daarna ""vertaald naar M"" in PQ", Int64.Type}}),
    #"Renamed Columns2" = Table.RenameColumns(#"Changed Type1",{{"Day", "Day Of Month"}}),
    #"Inserted Day of Year" = Table.AddColumn(#"Renamed Columns2", "Day of Year", each Date.DayOfYear([Date]), Int64.Type),
    #"Renamed Columns3" = Table.RenameColumns(#"Inserted Day of Year",{{"Week Index", "Week Index F"}}),
    #"Inserted Text After Delimiter" = Table.AddColumn(#"Renamed Columns3", "HRE ISO - WEEK", each Text.AfterDelimiter([#"Jaar(datum) + HRE ISO week"], "-"), type text)
in
    #"Inserted Text After Delimiter"
I hope this is helpful
Financial Performance Report
