DateTime::ISO8601 isn't ISO8601 compatible

[zoul0813]

Just discovered that DateTime::ISO8601 isn't compatible with the ISO8601 standard, PHP Docs state that you should use DateTime::ATOM to be compatible.

DateTime::ATOM
DATE_ATOM
Atom (example: 2005-08-15T15:52:01+00:00)

DateTime::ISO8601
DATE_ISO8601
ISO-8601 (example: 2005-08-15T15:52:01+0000)
Note: This format is not compatible with ISO-8601, but is left this way for backward compatibility reasons. Use DateTime::ATOM or DATE_ATOM for compatibility with ISO-8601 instead.

http://www.php.net/manual/en/class.datetime.php

The difference appears to be in how the TZ Offset at the end is formatted (0000 vs 00:00).