| Re: [chrony-dev] Fw: leap seconds correction |
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On Sun, 9 Feb 2014, Marek Behun wrote:
Hi,
I think there is a little misunderstanding here. I do not want to not
use leap seconds. I fully understand why they are applied and how the
systems work now. Again I suggest to read the first post at
http://forums.gentoo.org/viewtopic-t-980486.html where this idea is
explained more. I want to use another definition of UNIX time.
Current definition of UNIX time is this:
the number of seconds that have elapsed since 00:00:00 Coordinated
Universal Time (UTC), Thursday, 1 January 1970, not counting leap
seconds.
From Wikipedia: due to its handling of leap seconds, it is neither a
linear representation of time nor a true representation of UTC.
UTC is not TAI. UTC includes leap seconds. Ie, it is discontinuous.
Unix time is utc except if a second is lost, tnen during the course of that
second the unix clock always returns a greater time to successive requests for
time. Ie if there are not requests during that time, it returns utc always. If
there are more than one, then each will return a (slightly) later time.
I want to use this redefinition:
number of seconds that have elapsed since 00:00:00 UTC, Thursday, 1
January 1970, *counting leap seconds*.
Yes, you want TAI, not UTC.
That is certainly your right.
Currently I'm using openrdate with -c flag to do this. This way I can
use the right/Europe/Prague timezone and still have the same output of
$ date
as is on a server with posix/Europe/Prague at that exact moment if that
server doesn't use this kind of leap seconds corrections.
To conclude: I don't want to remove leap seconds. I want my UNIX
time ticks to tick continuosly, so when a leap second occurs, my UNIX
time won't stop for one second (or skip one), it will tick normally
through that leap second and the right/Europe/Prague timezone will then
compute the right time when formatting to human readable form. That way
I can for example compute the correct number of seconds elapsed between
two events. (And please don't tell me to use CLOCK_MONOTONIC, I am
talking about events happening on different machines and this is still
an example).
The implementation should be trivial: if the flag is present, count the
It is always nice to tell others that the work you want them to do is trivial.
If it is, do it.
Note it is equally trivial to do this in Userspace. When you want coninuous
time subtract the seconds and add the number of leap seconds from the file.
Looking up files should not be occuring on system space but in user space.
Someday you might persuade Unix to adopt TAI rather than UTC. I do not see
that as happening soon.
number of leap seconds from a leap second database and add that number
to the time received from time server. Openrdate does exactly that with
-c flag. But openrdate cannot synchronize from more timeservers and
uses settimeofday, so time update can still be non-continuous.
From the last post on that gentoo forum page:
This idea was presented at the first Future of UTC meeting in 2011,
and the problems faced by Linux kernels were documented at the second
meeting in 2013. See http://futureofutc.org/ for the full conference
proceedings, and see
http://www.ucolick.org/~sla/leapsecs/right+gps.html for more about
the code that can test this idea.
Marek Behun
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