Sure.
Iâve added comments in your Calendar function below, to explain what each step does.
You can also visualize the nested table that is created in your Dates table, by omitting the Table.RowCount in the InsertCustomWeek step - when you click in the white space, you can see a preview of the nested table. The number of rows in that table change with each week. And so we can use it to create a custom week number for each date.
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let fnDateTable = (StartDate as date, EndDate as date, FYStartMonth as number) as table =>
let
DayCount = Duration.Days(Duration.From(EndDate - StartDate)),
Source = List.Dates(StartDate,DayCount,#duration(1,0,0,0)),
TableFromList = Table.FromList(Source, Splitter.SplitByNothing()),
ChangedType = Table.TransformColumnTypes(TableFromList,{{"Column1", type date}}),
RenamedColumns = Table.RenameColumns(ChangedType,{{"Column1", "Date"}}),
InsertYear = Table.AddColumn(RenamedColumns, "Year", each Date.Year([Date]),type text),
InsertYearNumber = Table.AddColumn(RenamedColumns, "YearNumber", each Date.Year([Date])),
InsertQuarter = Table.AddColumn(InsertYear, "QuarterOfYear", each Date.QuarterOfYear([Date])),
InsertMonth = Table.AddColumn(InsertQuarter, "MonthOfYear", each Date.Month([Date]), type text),
InsertDay = Table.AddColumn(InsertMonth, "DayOfMonth", each Date.Day([Date])),
InsertDayInt = Table.AddColumn(InsertDay, "DateInt", each [Year] * 10000 + [MonthOfYear] * 100 + [DayOfMonth]),
InsertMonthName = Table.AddColumn(InsertDayInt, "MonthName", each Date.ToText([Date], "MMMM"), type text),
InsertCalendarMonth = Table.AddColumn(InsertMonthName, "MonthInCalendar", each (try(Text.Range([MonthName],0,3)) otherwise [MonthName]) & " " & Number.ToText([Year])),
InsertCalendarQtr = Table.AddColumn(InsertCalendarMonth, "QuarterInCalendar", each "Q" & Number.ToText([QuarterOfYear]) & " " & Number.ToText([Year])),
InsertDayWeek = Table.AddColumn(InsertCalendarQtr, "DayInWeek", each Date.DayOfWeek([Date])),
InsertDayName = Table.AddColumn(InsertDayWeek, "DayOfWeekName", each Date.ToText([Date], "dddd"), type text),
InsertWeekEnding = Table.AddColumn(InsertDayName, "WeekEnding", each Date.EndOfWeek([Date]), type date),
InsertWeekNumber= Table.AddColumn(InsertWeekEnding, "Week Number", each Date.WeekOfYear([Date])),
// Add a Week of Month column, where the week starts on Sunday
InsertWeekOfMonth = Table.AddColumn(InsertWeekNumber, "Week Number2", each Date.WeekOfMonth([Date], Day.Sunday)),
// Create a Unique Interger for each Week
InsertWkMnthNum = Table.AddColumn(InsertWeekOfMonth, "YMW number", each [Year] * 10000 + [MonthOfYear] * 100 + [Week Number2], type number),
// Load the disinct combination of the columns [Year] and [YMW number] into memory
BufferTable = Table.Buffer(Table.Distinct( InsertWkMnthNum[[Year], [YMW number]])),
// Count the rows in the Filtered BufferTable where [Year] = [Year] and [YMW number] <= [YMW number] on the current Record
InsertCustomWeek = Table.AddColumn(InsertWkMnthNum, "Custom Week no", (OT) => Table.RowCount( Table.SelectRows( BufferTable, (IT) => IT[YMW number] <= OT[YMW number] and IT[Year] = OT[Year]))),
InsertMonthnYear = Table.AddColumn(InsertCustomWeek,"MonthnYear", each [Year] * 10000 + [MonthOfYear] * 100),
InsertQuarternYear = Table.AddColumn(InsertMonthnYear,"QuarternYear", each [Year] * 10000 + [QuarterOfYear] * 100),
ChangedType1 = Table.TransformColumnTypes(InsertQuarternYear,{{"QuarternYear", Int64.Type},{"Week Number", Int64.Type},{"Year", type text},{"MonthnYear", Int64.Type}, {"DateInt", Int64.Type}, {"DayOfMonth", Int64.Type}, {"MonthOfYear", Int64.Type}, {"QuarterOfYear", Int64.Type}, {"MonthInCalendar", type text}, {"QuarterInCalendar", type text}, {"DayInWeek", Int64.Type}}),
InsertShortYear = Table.AddColumn(ChangedType1, "ShortYear", each Text.End(Text.From([Year]), 2), type text),
AddFY = Table.AddColumn(InsertShortYear, "FY", each "FY"&(if [MonthOfYear]>=FYStartMonth then Text.From(Number.From([ShortYear])+1) else [ShortYear]))
in
AddFY
in
fnDateTable