code: public static String prettyUptime(int secs) {
          String[][] PRETTYSECDIVIDERS = { new String[] { "s", "60" }, new String[] { "m", "60" }, new String[] { "h", "24" },
                  new String[] { "d", null } };
          int diversize = PRETTYSECDIVIDERS.length;
  
          LinkedList<String> tmp = new LinkedList<>();
          int div = secs;
          for (int i = 0; i < diversize; i++) {
              if (PRETTYSECDIVIDERS[i][1] != null) {
                  Integer d = Integer.parseInt(PRETTYSECDIVIDERS[i][1]);
                  tmp.addFirst(div % d + PRETTYSECDIVIDERS[i][0]);
                  div = div / d;
              } else {
                  tmp.addFirst(div + PRETTYSECDIVIDERS[i][0]);
              }
              if (div <= 0 ) break;
          }
  
          Joiner joiner = Joiner.on(" ");
          return joiner.join(tmp);
      }
docs: seconds to string like '30m 40s' and '1d 20h 30m 40s'
  
  @param secs
  @return