Returns a time mark on the same time source that is behind this time mark by the specified duration.
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 subtracted from an infinitely distant future time mark or
a negative infinite duration is subtracted from an infinitely distant past time mark.
Returns the duration elapsed between the other time mark and
this time mark.
The returned duration can be infinite if the time marks are far away from each other and
the result doesn't fit into Duration type,
or if one time mark is infinitely distant, or if both
this and other time marks
lie infinitely distant on the opposite sides of the time scale.
Two infinitely distant time marks on the same side of the time scale are considered equal and the duration between them is Duration.ZERO.
Note that the other time mark must be obtained from the same time source as this one.