ISO 8601 format or null in the case that there was an error. The string should be freed with glib.global.gfree.
DateTime.formatIso8601
string formatIso8601()Format datetime in ISO 8601 format, including the date, time and time zone, and return that as a UTF-8 encoded string.
Since GLib 2.66, this will output to sub-second precision if needed.
Returns
a newly allocated string formatted in