ietf-nntp Section 11.5 - NEWNEWS

[Russ Allbery]

Paul Overell <paulo at turnpike.com> writes:
> Clive D.W. Feather <clive at demon.net> writes

>> + The date and time are given in the server's approximation to UT
>> + (otherwise known as GMT).

No, it's not; it's UTC.  The only reason why it was called GMT was because
folks didn't understand the technical difference between GMT and UTC.
Most server implementations that I'm familiar with use gmtime to obtain
the information, and on nearly all Unix systems this will return UTC (on
some, it will return TAI).

>> + The server is not required to track leap seconds or UT/TAI/UTC
>> + variations exactly, nor need the server's clock be accurate to within
>> + 1 second.

As long as it's clear that if the server is actually keeping TAI, the news
server software isn't required to convert that to UTC.  We don't want to
go there, and it's very reasonable (and more useful for some applications)
to set a Unix system clock to track TAI instead of UTC.  I know quite a
few people who do so.

> I think invoking UT/TAI/UTC/ is muddying the waters.  It's in UTC (not
> UT, not TAI, not POSIX).  Saying what accuracy is not required doesn't
> say what accuracy is required.  I suggest:

>         The date and time are given in UTC.  The date and time SHOULD be
>         accurate.

> Using "SHOULD" gives the server the get-out if they can't support leap
> seconds or if their clock drifts a bit, but if they can get it right
> then they SHOULD.

Yeah, but you're implying to the client author more accuracy than may be
there; if the server is actually keeping TAI, the clock could easily be
off from UTC by half a minute or more.

-- 
Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>