code: public static void validateTime(String timestamp, int duration) throws Exception {
          Date date = getTimestampFormatter().parse(timestamp);
          long sign_time = date.getTime();
          long now_time = System.currentTimeMillis();
          long diff = now_time - sign_time;
          long min_diff = diff / (60 * 1000);
          
          if (min_diff >= duration) {
              throw new GeneralSecurityException("Authorization token has expired.");
          }
      }
docs: Validates the timestamp and insures that it falls within the specified duration.
  
  @param timestamp Timestamp in yyyyMMddHHmmssz format.
  @param duration Validity duration in minutes.
  @throws Exception Unspecified exception.