Code:

function RoundTime(ADate: string; Rounding: Integer; bRound: Boolean): string;

var

Year, Month, Day, Hour, Min, Sec, MSec: Word;

tmpDate: TDateTime;

Res, Diff: string;

M: integer;

begin

tmpDate := StrToDateTime(ADate);

DecodeTime(tmpDate, Hour, Min, Sec, MSec);

if (Rounding > 0) and (bRound = True) then

begin

if Min mod Rounding = 0then

Res := IntToStr(Min)

else

Res := IntToStr(Round(Min / Rounding) * Rounding);

M := StrToInt(Copy(ADate, Length(ADate) - 1, 2));

Diff := IntToStr(StrToInt(Res) - M);

if Copy(Diff, 1, 1) = '-'then

begin

Diff := Copy(Diff, 2, Length(Diff) - 1);

Result := FormatDateTime('dd.mm.yy hh:mm', (tmpDate - StrToTime('00:00' + Diff)));

end

else

Result := FormatDateTime('dd.mm.yy hh:mm', (tmpDate + StrToTime('00:00' + Diff)));

end

else

Result := ADate;

end;

// Example:

procedure TForm1.Button1Click(Sender: TObject);

begin

Edit1.Text := FormatDateTime('dd.mm.yy hh:mm', Now);

Edit2.Text := RountTime(Edit1.Text, SpinEdit1.Value, Checkbox1.Checked);

// Example: RoundTime('07.08.02 10:41', '15', True) -- > 07.08.02 10:45

end;