Identified is a need to define a duration property, which is published by several individuals but with no clear definition.

See Discussion in snarfed/granary#169 summarized below.

The proposed definition is the duration of an audio or video file in the entry, however duration is also used for other items, so it should be only the duration of an audio or video file if there is a video/audio property.

Should the value be the ISO8601 duration format, the derived HTML duration, or just integer seconds? Also, the proposal note in the wiki states p-duration, where it probably should be dt-duration, to match h-event.

iCal and hCalendar use ISO8601 duration format, Media RSS uses seconds. Whatever format is adopted for h-event should be adopted for h-entry for consistency.

Related: http://microformats.org/wiki/h-event defines duration with no format defined. See microformats/h-event#7