Breaks with the iso8601 standard for duration

[nutgaard]

Decimal numbers should be allowed in the format, e.g: P0.5Y and PT0.123S.
This Z designator does however not exists in ISO8601-duration (ref: ISO8601 3.4), and may for all intents and purposes be removed since it is only used as a UTC designation(ISO8601 4.2.4).

http://dotat.at/tmp/ISO_8601-2004_E.pdf