Delphi Get previous month and year

Hi, this is the easiest way to do it

procedure TForm1.Button1Click(Sender: TObject);
begin
 ShowMessage(DateToStr(IncMonth(now, -1)));
end;

This will get a date with previous month. If you want previous year substract 12 months

If you want to use you date format, try this

function GetPreviousDate(IntDate: Integer): string;
var Year, Month: word;
begin
Year := StrToInt(Copy(IntToStr(IntDate), 1, 4));
Month := StrToInt(Copy(IntToStr(intDate), 5, 2));
if Month = 1 then result := IntToStr(Year - 1) + '12'
else result := IntTostr(year) + IntToStr(Month - 1);
end;

procedure TForm1.Button1Click(Sender: TObject);

begin
showmessage(GetPreviousDate(201001)) ;
end;

It appears that, although you said you wanted the "previous month and year", you actually want the previous month and, if the current month is January, you want December of the previous year.
 In that case, twinsoft's solution is the correct one.
Now, if you want to be able to do something like display the year in one TEdit control and the month in another and then selectively either subtract one year or one month, you can accomplish that with the following code.
 

procedure TForm1.SubtractYearClick(Sender: TObject);
begin
 ShowMessage(DateToStr(IncYear(now, -1)));
end;

procedure TForm1.SubtractMonthClick(Sender: TObject);
begin
 ShowMessage(DateToStr(IncMonth(now, -1)));
end;

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@henryreynolds

If I read your question correctly, you have a string that contains yyyymm value and you need to calculate/output the yyyymm value for the prior month.

First, you will need to convert your yyyymm sting into a date, using the first day of the month as a default.  Then pass that date value to a version of the twinsoft routine (from http:#28531199).
IncMonth(converteddatevalue, -1)

Next, you will need to format that prior month's date back into yyyymm format.

Thank you very much

@ henryreynolds

Are you sure you meant to accept that comment and not the one above it?