code: public void initTimestamp() throws ChronosException, FatalChronosException {
      maxAssignedTimestamp = chronosServerWatcher.getPersistentTimestamp();
      long newPersistentTimestamp = maxAssignedTimestamp + zkAdvanceTimestamp;
      chronosServerWatcher.setPersistentTimestamp(newPersistentTimestamp);
      LOG.info("Get persistent timestamp " + maxAssignedTimestamp + " and set "
          + newPersistentTimestamp + " in ZooKeeper");
    }
docs: Get the persistent timestamp in ZooKeeper and initialize the new one in ZooKeeper.
  
  @throws ChronosException when error to set value in ZooKeeper
  @throws FatalChronosException when set a smaller timestamp in ZooKeeper