Duration is currently included in the draft spec at http://www.loc.gov/standards/datetime/spec.html
in features 003 and 005.
In 005, the end endpoint of an interval is expressed as a duration rather than a date. But a date/duration interval can always be converted to a date/date interval and so it seems that there is no real need for this feature.
003 specifies standalone duration, for example "five years, two months". In recent discussion it has become clear that there is more work to do to sort out normalization rules, even perhaps to establish a model for duration. The only participant in that discussion have been Saašha and myself, and nobody else seems interested, so perhaps there is no need for duration in the spec, in either form, and if not then we can avoid unnecessary work.
So, if you see a need for duration, speak up, otherwise I plan to eliminate it from the spec.
> -----Original Message-----
> From: Discussion of the Developing Date/Time Standards
> [mailto:[log in to unmask]] On Behalf Of Ray Denenberg
> Sent: Thursday, July 14, 2011 4:20 PM
> To: [log in to unmask]
> Subject: Re: [DATETIME] duration normalization rules
> From: Saašha Metsärantala
> > I would like to ask whether we need CONTEXTUAL duration AS OF #005?
> > there a point with a start-duration interval (as of #005) if it
> > can be rewritten as a start-end interval as of #004?
> Yes it seems that we're not sure that we have any use case for duration,
> either contextual or standalone, and, given the complexity with respect
> to its normalization, we should consider eliminating it from the spec.