Need get Time in a 24 hour format while adding Time

Question

I had written a function for Adding time as given below

private void Delay15Minute() {
        String pkManifest = manifest.pkManifestNo;
        manifest_helper = new manifest_helper(this);
        cursor = manifest_helper.GetDeliveries(pkManifest);
        cursor.moveToFirst();
        for (int i = 0; i < cursor.getCount(); i++) {
            cursor.getString(cursor.getColumnIndex("PKDelivery"));
            // String
            // RevisedTime=cursor.getString(cursor.getColumnIndex("RevisedEstimatedDeliveryTime"));
            String RevisedTime = "12:55";

            // get hour and minute from time string
            StringTokenizer st1 = new StringTokenizer(RevisedTime, ":");
            int j = 0;
            int[] val = new int[st1.countTokens()];
            // iterate through tokens
            while (st1.hasMoreTokens()) {
                val[j] = Integer.parseInt(st1.nextToken());
                j++;
            }
            // call time add method with current hour, minute and minutesToAdd,
            // return added time as a string
            String date = addTime(val[0], val[1], 15);
            // Tioast the new time
            Toast.makeText(this, "date is =" + date, Toast.LENGTH_SHORT).show();

        }
            }



public String addTime(int hour, int minute, int minutesToAdd) {
        Calendar calendar = new GregorianCalendar(1990, 1, 1, hour, minute);
        calendar.add(Calendar.MINUTE, minutesToAdd);
        SimpleDateFormat sdf = new SimpleDateFormat("hh:mm");
        String date = sdf.format(calendar.getTime());

        return date;
    }

I am getting the oupt of this as 01:10 as 12 hours fromat...

I need to get it in 13:10 format ie 24 hour format.....Please help me