Title: AdvanceDateByOneMonth function + DaysInMonth
Question: Need a function to advance a date by one month, taking into account going from the last day of a 30 day month to the last day of a 31 day month, and visa versa, and February?
This is a simple function, but hopefully it will help someone.
Answer:
function daysInMonth(iMonth, iYear: Integer): Integer;
begin
if iMonth in [1,3,5,7,8,10,12] then
Result := 31
else if (iMonth in [4,6,9,11]) then
Result := 30
else if isLeapYear(iYear) then
Result := 29
else
Result := 28;
end; // daysInMonth
function advanceDateByOneMonth(dd: TDateTime): TDateTime;
var
iYear, iMonth, iDay, iOldMonth, iOldYear: Word;
begin
DecodeDate(dd, iYear, iMonth, iDay);
iOldMonth := iMonth;
iOldYear := iYear;
Inc(iMonth);
if iMonth = 13 then begin
iMonth := 1;
Inc(iYear);
end;
{if last day of month is used then
make the next date the last day of next month}
if daysInMonth(iOldMonth, iOldYear) = iDay then
iDay := daysInMonth(iMonth, iYear);
Result := EncodeDate(iYear, iMonth, iDay);
end; // advanceDateByOneMonth