[tz] Fwd: New Version Notification for draft-murchison-rfc8536bis-06.txt

[Paul Eggert]

In rereading the draft I found a couple of technical issues.

1. Most of this draft was written before the recent announcement that 
leap seconds are possibly being discontinued. As I understand it, this 
proposal is likely but not yet set in stone. Perhaps we need a sentence 
or two about this in the draft? Something like the following at the 
first mention of leap second expiry:

"If leap seconds become permanently discontinued, as requested by the 
General Conference on Weights and Measures[*], the leap second table 
SHOULD NOT expire since it will not be updated in the foreseeable future."

and cite Resolution 4 of the 27th CGPM (2022) 
<https://www.bipm.org/en/cgpm-2022/resolution-4>.


2. The use of TZ strings like 'XXX3EDT4,0/0,J365/23' is described 
confusingly, since 3.3.1 says that this is not an extension to POSIX 
(i.e., we're just spelling out what POSIX says, so this is not a TZ 
string extension), whereas the title of 3.3.1 says "TZ String 
Extensions". Because section 4 says a writer should generate a version 3 
file (which can contain TZ string extensions) only if necessary, it's 
too easy to read this as saying that if the TZif file contains a TZ 
string like 'XXX3EDT4,0/0,J365/23' then it must be at least version 3 - 
which is not how current zic behaves (it's just version 2). (This 
confusion is my fault; sorry.)

To fix this, how about if we move the text and example in the bullet 
point "* DST is considered to be in effect all year ..." up from section 
3.3.1 to section 3.3, with minor wordsmithing to continue to make it 
clear that we're only spelling out POSIX more explicitly, not extending 
it. As a result of this wordsmithing, there will only be one POSIX 
extension (extending hours to -167 through 167).

I suppose we should also should note that a future version of POSIX is 
likely to adopt the POSIX extension documented in 3.3.1. Even if that 
happens, 3.3.1 will still considered to be an extension, in that TZif 
files using it will still need to be marked version 3 or later.