code: def _probe_lock_file(self, reported_mtime):
          
          delta = reported_mtime - self.lock_data["lock_time"]
          # delta2 = reported_mtime - self.lock_write_time
          self.server_time_ofs = delta
          if self.get_option("verbose", 3) >= 4:
              write("Server time offset: {:.2f} seconds.".format(delta))
docs: Called by get_dir