Should a format for duration be specified? #5
Description
Inspired by snarfed/granary#169. mf1 (both [hAudio](http://microformats.org/wiki/haudio and hCalendar) used to recommend ISO 8601 durations for duration properties. This made it clear for both authors and consumers what sort of value they could expect.
Currently we do not specify any duration format for h-event’s dt-duration. Would it be a good idea if we did?
I would lean towards specifying HTML’s duration syntax. This will mean it stays compatible with HTML datetime properties.