code: public Date estimateLockTime(AbstractBlockChain chain) {
          if (lockTime < LOCKTIME_THRESHOLD)
              return chain.estimateBlockTime((int)getLockTime());
          else
              return new Date(getLockTime()*1000);
      }
docs: Returns either the lock time as a date, if it was specified in seconds, or an estimate based on the time in
  the current head block if it was specified as a block time.