// Create a calendar object of the desired month out.println(dateSplit[2]); out.println(dateSplit[0]); out.println(dateSplit[1]); Calendar cal = new GregorianCalendar(Integer.parseInt(dateSplit[2]), Integer.parseInt(dateSplit[0]), Integer.parseInt(dateSplit[1])); // Get the number of days in that month int days = cal.getActualMaximum(Calendar.DAY_OF_MONTH); // 28 out.println("days: "+days);