Fair point, I don't know..
On the other hand, Oracle has it..
And if I interpret what it says there correctly (without my brain getting fuzzy)...
"Time zone offset: The string '(+|-)HH:MM' specifies a time zone as an offset from UTC. For example, '-07:00' specifies the time zone that is 7 hours behind UTC. For example, if the UTC time is 11:00 a.m., then the time in the '-07:00' time zone is 4:00 a.m."
I THINK that is saying it is NOT Posix, but ISO... or the opposite of what postgresql does... I'd like to argue therefore postgresql is "wrong", though no doubt that will make some people mad. In ISO land, a negative offset has an earlier time than UTC, and a positive offset has a later time than UTC, so if UTC is 11am, and UTC-7 is 4 am (like America), then that's ISO format.
Microsoft land has it:
Now I can't see an explicit statement on whether that is Posix or ISO, however it does mention that zones are interpreted according to the windows registry:
KEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones
and if you look in there, it says Vladivostok UTC+10, so almost certainly this is an ISO setup.
I'm starting to think that it's basically a defacto SQL standard, if not actually an SQL standard, and it should be ISO, not Posix. I'm tempted to argue that even UTC+- should be changed to conform.
Highly doubtful that any production code cares about doing that, but having sensible output is useful for ad hoc queries.
