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    SubjectRe: Bug: Status/Summary of slashdot leap-second crash on new years 2008-2009
    2009/1/5 David Newall <davidn@davidnewall.com>:

    > Zoneinfo files cater for leap seconds.

    As has been (repeatedly) pointed out, the leap seconds
    only apply to UTC, so there is no way, given UTC, to
    use a zoneinfo file to twiddle UTC.

    Your argument *might* work if the kernel maintained
    TEI instead of UTC. Then there could, in principle, be
    a zoneinfo file that converted from TEI to UTC (by
    adding 24 seconds to TEI).

    However, this requires converting the kernel to track
    TEI instead of UTC, and reviewing all sorts of code
    in the kernel, glibc, ntp, and myriads of other libraries
    to figure out what's affected and whats not. As well
    as figuring out how to twiddle zoneinfo files so that
    they're backwards/forwards compatible with the
    timekeeping change, so that users aren't screwed
    when they put new kernels on old distros, or new
    zonefiles on old kernels.

    This is a fairly big chunk of work, requiring coordination
    between lots of different parties.

    > If you know in advance, you can update zoneinfo files with multiple leap
    > seconds.

    Heh. You miss the point. The whole point of leap seconds
    is that they're unknowable in advance. You only know if they
    already happened, or seem likely to happen real soon now.
    The previously cited wikipedia article reviews this nicely.

    --linas

    p.s. Yes, you could say I'm coming around to your point
    of view. If you had said, from the begining, something
    like "the kernel should keep TEI instead of UTC, and
    compute UTC in user-space from the TEI time", then
    you might have met a lot less resistance. But that's not
    how your argument came across.


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