// Aquí guardo el tiempo.
    mp.getLongs().put(item.getName(), new Date().getTime());

// Así hago un check de si ya ha pasado el tiempo y si no, obtengo lo que falta
    long timestampNow = System.currentTimeMillis() / 1000;
    long expires = mp.getLongs().get(item.getName());
    if(timestampNow >= expires){
          mp.getLongs().remove(item.getName());
    }else{
          expires = (long) expires * 1000;
          String formatExpires = Utils.formatDateDiff(expires);
    }
// Esto me devuelve un String con el tiempo dividido en años, meses, días, horas, minutos y segundos:
    public static String formatDateDiff(Calendar fromDate, Calendar toDate){
          boolean future = false;

          if (toDate.equals(fromDate)) {
            return "1 segundo";
          }
          if (toDate.after(fromDate)) {
            future = true;
          }

        StringBuilder sb = new StringBuilder();
        int[] types = new int[] { Calendar.YEAR, Calendar.MONTH, Calendar.DAY_OF_MONTH, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND };
        String[] names = new String[] { "año", "años", "mes", "meses", "día", "días", "hora", "horas", "minuto", "minutos", "segundo", "segundos" };
        for (int i = 0; i < types.length; i++) {
            int diff = dateDiff(types[i], fromDate, toDate, future);
            if (diff > 0) {
                sb.append(" ").append(diff).append(" ").append(names[i * 2 + (diff > 1 ? 1 : 0)]);
            }
        }
        if (sb.length() == 0) {
            return "1 segundo";
        }
        return sb.toString().trim();
    }

    public static String formatDateDiff(long date) {
        Calendar now = new GregorianCalendar();
        Calendar c = new GregorianCalendar();
        c.setTimeInMillis(date);
        return formatDateDiff(now, c);
    }