joevandyk/ruby-duration — pull request #1 by joevandyk (2012-06-23 05:47:01+00:00)
Title: Iso8601

I'm not an ISO8601 expert, but it appears many implementations ignore
weeks in the format string. The Ruby iso8601 library does, and
postgresql does as well:

select interval '1w';
interval
----------
P7D

In order to better operate with those libraries, this library no longer
includes the week in the iso8601 format.