I want to represent a time interval as start/end but also while taking advantage of the abbreviations that ISO 8601 seems to allow: for interval end fields that are the same as in the starting point. For example, the interval starting right now and lasting a week would be 2016-06-08T12:27Z/15T12:27 (note the omission of a second "2016-06-").
To ward of potential XY-problem second-guessing: I don't want this interval represented as 2016-06-08T12:27Z/P1W, even if it is shorter. I do want the end time represented directly, but abbreviated to the extent possible.
I don't think DatePeriod does what I want - does it? It seems to either do half the job (start and end independently, with no possibility for abbreviation) or the wrong job (returning a duration, not an end time).