[LEAPSECS] What's the point?

Warner Losh imp at bsdimp.com
Tue Feb 8 20:22:04 EST 2011

On 02/08/2011 17:19, Steve Allen wrote:

> On Tue 2011-02-08T17:03:31 -0700, Warner Losh hath writ:

>> NTP also does everything in UTC time

> No, NTP does not use UTC per se.

> The existing implementations make that specification misleading.

> Rather, NTP uses the internationally approved broadcast time scale.

> The implementations do not know the name of that time scale.

> Only the documentation knows that.


> (This is, of course, discounting those site whose sensitivity

> to leap seconds is so great that they are using some sort of

> GPS-based or TAI-based master timeserver for their NTP.)

Pedantically correct, but ntp networks operating in those modes are the
exception, rather than the rule. At least with the prevalence of
GPS-based ntp-servers, setting up a GPS-time network is quite a bit
easier to pull off than years ago...

> The point of my suggestion for using zoneinfo to propagate the leap

> seconds is that both NTP and POSIX would de facto, silently, and

> inconsequentially change to using TI rather than UTC if the name of

> the internationally approved time scale changed to that. The systems

> would keep working just fine -- even better if they do not like leaps.

Yes, that would work. If there were no more leap seconds then this
would be a workable solution. only because you don't have either the
restart or the stale leap data to worry about.

> The documentation could be fixed up later, and the situation would not

> be any more confusing than it is now.

The biggest problem I have with the current state of the art is the need
to restart programs when new zone files arrive. At least that was the
state of the art last time I studied this code in detail, which was
about 3 years ago. The second biggest problem I have is using stale
leap second data to do things like set the current system time before
you can get the latest info, at which point you're painted into a corner
with few good solutions.


> --

> Steve Allen<sla at ucolick.org> WGS-84 (GPS)

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