On Feb 7, 2021, at 12:47 AM, Tom Honermann via Lib-Ext <lib-ext@lists.isocpp.org> wrote:

  1. References:
    1. This is more of a question for LWG.  The IANA registry is not versioned, but does contain a last updated time stamp.  No stability guarantees are provided, nor is there an obvious way to access older revisions of the registry.  Is a reference ok?  Or do we need to include the contents in the standard?  The IANA registry had not been updated for many years until just a month ago when "UTF-7-IMAP" was added.

IANA is already referenced in the bibliography and the chrono sections of the standard in relation to the time zone interface. There’s no versions or stability there either — just a link. Howard can probably clarify, but pretty sure all that was intentional to avoid instability in the c++ spec — that is stay out of the quagmire or ever changing time zone data. 

The difference I see is that P1885, as currently drafted, basically pulls in ’the list of encodings' from IANA, where chrono completely dodges doing anything of the sort. Not sure there’s a way to achieve the goals of P1885 without that, but it’s clearly more dependent than chrono.