UFN_DAYOFMONTH_DESCRIPTION

CREATE function dbo.UFN_DAYOFMONTH_DESCRIPTION(
    @DAYOFMONTH smallint = NULL
)
returns nvarchar(10)
with execute as caller
as begin
    declare @DESC nvarchar(10);    
    declare @MOD smallint;

    if @DAYOFMONTH=29 
        set @DAYOFMONTH=NULL;

    set @MOD = @DAYOFMONTH % 10;
    if (@DAYOFMONTH>3 and @DAYOFMONTH<20) or (@MOD=0 or @MOD>=4)
        set @DESC = CONVERT(nvarchar,@DAYOFMONTH) + 'th';
    else if @DAYOFMONTH = 1 
        set @DESC = 'First';
    else if @MOD = 1 
        set @DESC = CONVERT(nvarchar,@DAYOFMONTH) + 'st';
    else if @MOD = 2 
        set @DESC = CONVERT(nvarchar,@DAYOFMONTH) + 'nd';
    else if @MOD = 3 
        set @DESC = CONVERT(nvarchar,@DAYOFMONTH) + 'rd';
    else 
        set @DESC = 'Last';

    return @DESC;
end