@SuppressWarnings ("javadoc")
	final FEMDuration _move_(final int durationmonths, final long durationmillis) throws IllegalArgumentException {
		if (this.signValue() < 0) return FEMDuration.from(durationmonths - this.durationmonthsValue(), durationmillis - this.durationmillisValue());
		return FEMDuration.from(durationmonths + this.durationmonthsValue(), durationmillis + this.durationmillisValue());
	}