Format @datetime in ISO 8601 format, including the date, time and time zone, and return that as a UTF-8 encoded string.
a newly allocated string formatted in ISO 8601 format or %NULL in the case that there was an error. The string should be freed with g_free().
2.62
See Implementation
Format @datetime in ISO 8601 format, including the date, time and time zone, and return that as a UTF-8 encoded string.