public String monthL(String field)
    {
         
         String newField = "";

          for(int i = 1; i <= field.length(); i++)
          {
                 if(isNumber(field.substring(i - 1, i)))
                {
                    newField = newField + field.substring(i - 1, i);
                }
                else
                {
                     newField = "~invalid~";
                     break;
                }

                 boolean over = false;

                 try
                 {
                     if(Integer.parseInt(newField) > 31)
                     {
                         over = true;
                     }

                 }catch(Exception e)
                 {
                     System.out.println("not a integer");
                 }

                if(over)
                {
                    newField = "~invalid over~";
                    break;
                }
          }
         return newField;
     }