title: How to add number of days to a date in jalali(shamsi) calendar
body: <p>I am developing a java app in which I need to get a date and number of days from the user and then add this numbers to the date and show the final date which in this case would be the deadline date , to the user.
  The problem here is that I'm using <strong>shamsi(jalali) calendar</strong> and in order to the calculation , first I have to convert the shamsi date to java standar calendar then add the day numbers and again convert it back to shamsi date.</p>
  
  <pre><code>Date miladiDate = new Date(DateConvertor.shamsi2miladi(entity.getDoDate()));
  
  SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
  Calendar c = Calendar.getInstance();
  c.setTime(miladiDate);
  c.add(Calendar.DATE, baseEvaluate.getDeadLineDays());
  String output = sdf.format(c.getTime());
  System.out.println(output);
  entityDetail.setDeadLineDate(DateConvertor.miladi2date(c.getTime()));
  </code></pre>
  
  <p>I wanted to know if there is a way in which I could do this without converting the shamsi date , and just add the day number to the shamsi date.
  P.S : I used joda time , it does not support the shamsi calendar.</p>