duration

  is an emerging microformats2 property that indicate the time duration of audio and/or video properties in the same item. is an alias.

Examples in the wild have used both ISO 8601 duration (eg ) values and integer seconds values.

How to publish
Use a  element with either integer number of seconds or ISO 8601 duration in the   attribute, and any human-readable representation you choose in the contents. Example:

IndieWeb Examples

 * : details
 * : details

Granary
granary converts podcast h-feeds and h-entries to RSS with enclosures, including iTunes extension elements.

It reads episode duration from the  and   mf2 properties, and supports both integer seconds and ISO 8601 duration values. It emits the  mf2 property with integer seconds value. Background discussion.