code: @Override
      public int compareTo(Timestamp other) {
  	if (unixSec < other.unixSec) {
              return -1;
          } else if (unixSec == other.unixSec) {
              if (nanoSec < other.nanoSec) {
                  return -1;
              } else if (nanoSec == other.nanoSec) {
                  return 0;
              } else {
                  return 1;
              }
          } else {
              return 1;
          }
      }
docs: Defines the natural ordering for timestamp as forward in time.
  
  @param other another object
  @return comparison result