In several projects I have worked on we have used
YYYY-MM-DDThh:mm:ssUTC
e.g.
2017-01-01T12:00:00UTC
as the time-format and claimed it (incorrectly?) to be a compliant subset of ISO-8601.
It is clear that ISO-8601 includes Z and +hhmm as legal ways of specifying the offset from UTC and thereby the time-zone (ignoring daylight savings).
It seems clear that the W3C and most other organisations adopting (subsets of) ISO-8601 prefer to use Z (and +hhmm).
I'm looking for someone familiar with or better yet owning a copy of ISO-8601 to confirm whether or not it is conformant to use any time-zone abbreviation at all and UTC in particular (as a synonym for zulu-time 'Z').
I believe IANA is responsible for time-zones and ISO-8601 uses offsets only to avoid having to deal with the issue of time-zones changing.
I found an older version of the standard here which does not mention time-zone abbreviations. I would like confirmation that it is is not valid in the current standard (ISO-8601:2004?) to use UTC and claim ISO-8601 conformance.
I have ISO-8601:2004, which according to Wikipedia is the latest edition. I do not see that it allows the use of UTC in place of Z, though it mentions "UTC" quite often in the specification.