code: public int getDays() {
  		switch (_units) {
  		case Days:
  			return _amount;
  		case Weeks:
  			return _amount * 7;
  		case Months:
  			if (_amount <= 1)
  				return _amount * 30;
  			else if (_amount < 12)
  				return (_amount * 61) / 2;
  			else
  				return (_amount * 365) / 12;
  		default:
  			throw new UnsupportedOperationException();
  		}
  	}
docs: Get amount of this Duration in days
  @return