Returns a time mark on the same time source that is ahead of this time mark by the specified duration.
The returned time mark is more late when the duration is positive, and more early when the duration is negative.
If the time mark is adjusted too far in the past or in the future, it may saturate to an infinitely distant time mark. In that case, elapsedNow will return an infinite duration elapsed from such infinitely distant mark.
IllegalArgumentException - an implementation may throw if a positive infinite duration is added to an infinitely distant past time mark or
a negative infinite duration is added to an infinitely distant future time mark.