function setReleaseTime(address _holder, uint256 _release_time)
    public
    onlyOwner
    returns (bool)
  {
    require(_holder != address(0));
	require(_release_time >= block.timestamp);

	uint256 old_release_time = userLock[_holder].release_time;

	userLock[_holder].release_time = _release_time;
	emit LockTimeSetted(_holder, old_release_time, userLock[_holder].release_time);
	return true;
  }