Verbiage re: durations in rules
It would make more sense IMO to say that durations are an alternative way to specify an end for in_range operations (via calculation), and then provide an example. By supplying a duration, you are in effect supplying an end. The syntax is the same:
date in_range to
date in_range to duration ...
This is related to BZ 1662378. By addressing this BZ, that BZ should no longer be relevant.