Custom Date table

Anonymous-

Something like the below should help in your desired outcome (this is setup for my organizations FY; you'll need to modify for yours):

let
    Calendar = #table(
    type table
        [
            #"PeriodStart" = date,
            #"PeriodEnd" = date
        ],
    {
                { #date ( 2017, 06, 01 ), #date ( 2017, 6, 30 ) },
		{ #date ( 2017, 07, 01 ), #date ( 2017, 8, 1 ) },
		{ #date ( 2017, 08, 02 ), #date ( 2017, 8, 31 ) },
		{ #date ( 2017, 09, 01 ), #date ( 2017, 9, 30 ) },
		{ #date ( 2017, 10, 01 ), #date ( 2017, 10, 31 ) },
		{ #date ( 2017, 11, 01 ), #date ( 2017, 11, 30 ) },
		{ #date ( 2017, 12, 01 ), #date ( 2017, 12, 31 ) },
		{ #date ( 2018, 01, 01 ), #date ( 2018, 1, 30 ) },
		{ #date ( 2018, 01, 31 ), #date ( 2018, 2, 28 ) },
		{ #date ( 2018, 03, 01 ), #date ( 2018, 3, 31 ) },
		{ #date ( 2018, 04, 01 ), #date ( 2018, 4, 30 ) },
		{ #date ( 2018, 05, 01 ), #date ( 2018, 5, 30 ) },
		{ #date ( 2018, 05, 31 ), #date ( 2018, 6, 30 ) },
		{ #date ( 2018, 07, 01 ), #date ( 2018, 7, 31 ) },
		{ #date ( 2018, 08, 01 ), #date ( 2018, 8, 30 ) },
		{ #date ( 2018, 08, 31 ), #date ( 2018, 9, 30 ) },
		{ #date ( 2018, 10, 01 ), #date ( 2018, 10, 30 ) },
		{ #date ( 2018, 10, 31 ), #date ( 2018, 11, 29 ) },
		{ #date ( 2018, 11, 30 ), #date ( 2018, 12, 31 ) },
		{ #date ( 2019, 01, 01 ), #date ( 2019, 1, 30 ) },
		{ #date ( 2019, 01, 31 ), #date ( 2019, 2, 28 ) },
		{ #date ( 2019, 03, 01 ), #date ( 2019, 3, 31 ) },
		{ #date ( 2019, 04, 01 ), #date ( 2019, 4, 30 ) },
		{ #date ( 2019, 05, 01 ), #date ( 2019, 5, 30 ) },
		{ #date ( 2019, 05, 31 ), #date ( 2019, 6, 30 ) }
    }
),
    #"Added Index" = Table.AddIndexColumn(Calendar, "PeriodID", 1, 1),
    #"Added DatesBetween" = Table.AddColumn(#"Added Index", "Date", each List.Transform( { Number.From ( [PeriodStart] ) ..Number.From ( [PeriodEnd] ) }, each Date.From (_) ) ),
    #"Expanded Date" = Table.SelectColumns(Table.TransformColumnTypes(Table.ExpandListColumn(#"Added DatesBetween", "Date"),{{"Date", type date}}),{"PeriodID", "Date"}),
    #"Expanded EndOfWeek" = Table.TransformColumnTypes(Table.SelectColumns(Table.ExpandTableColumn(Table.AddIndexColumn(Table.Group( Table.AddColumn(#"Expanded Date", "End of Week", each Date.EndOfWeek([Date]), type date), {"End of Week"}, {{"EndOfWeek", each _, type table}}), "EndOfWeekID", 1, 1), "EndOfWeek", {"PeriodID", "Date"}, {"PeriodID", "Date"}),{"PeriodID", "EndOfWeekID", "Date" }),{{"PeriodID", Int64.Type},{"EndOfWeekID", Int64.Type},{"Date", type date}}),
    #"Added FiscalYearPeriodNum" = Table.AddColumn(#"Expanded EndOfWeek", "FiscalYearPeriodNum", each if Number.Mod([PeriodID], 12) = 0 then 12 else Number.Mod([PeriodID], 12), Int64.Type),
    #"Added FiscalYearPeriodName" = Table.AddColumn(#"Added FiscalYearPeriodNum", "FiscalYearPeriodName", each fnSwitchPeriodNumToName([FiscalYearPeriodNum]), type text),
    #"Added FiscalYearNum" = Table.AddColumn(#"Added FiscalYearPeriodName", "Fiscal Year", each if [FiscalYearPeriodNum] <= 7 then Date.Year([Date]) else Date.Year([Date]) - 1, Int64.Type),
    #"Added FiscalYearPeriodID" = Table.AddColumn(#"Added FiscalYearNum", "FiscalYearPeriodID", each ([Fiscal Year] * 100) + [FiscalYearPeriodNum], Int64.Type),
    #"Added FiscalYearPeriodCombined" = Table.RemoveColumns(Table.AddColumn(#"Added FiscalYearPeriodID", "Fiscal Year Period", each Text.Combine({Text.PadStart(Number.ToText([FiscalYearPeriodNum]), 2, "0"), [FiscalYearPeriodName]}, "-"), type text),{"FiscalYearPeriodNum", "FiscalYearPeriodName"})
in
    #"Added FiscalYearPeriodCombined"

You may also need the function below:

(input) =>

let

values = {

{1, "Jul"},
{2, "Aug"},
{3, "Sep"},
{4, "Oct"},
{5, "Nov"},
{6, "Dec"},
{7, "Jan"},
{8, "Feb"},
{9, "Mar"},
{10, "Apr"},
{11, "May"},
{12, "Jun"},
{input, "Undefined"}

},

Result = List.First(List.Select(values, each _{0}=input)){1}

in

Result