public User(String userName, 
				String firstName, 
				String lastName,
				Date dateOfBirth, 
				String emailAddress,
				Date passwordExpiryDate) {
		
		super();
		this.userName = userName;
		this.firstName = firstName;
		this.lastName = lastName;
		
		//making defensive copy
		if (dateOfBirth != null) {
			this.dateOfBirth = new Date(dateOfBirth.getTime());			
		} else {
			this.dateOfBirth = null;
		}

		this.emailAddress = emailAddress;
		
		//making defensive copy
		if (passwordExpiryDate != null) {
			this.passwordExpiryDate = new Date(passwordExpiryDate.getTime());			
		} else {
			this.passwordExpiryDate = null;
		}
	}