[time-nuts] FW: Bulletin C number 30

Warner Losh imp at bsdimp.com
Mon Jul 4 16:42:49 EDT 2005

> Fact is, time measurement _is_ based on geophysics, and the absence
> of leap seconds wouldn't make it "universal" in any way. That being
> the case, it is not unreasonable to keep it properly aligned. Leap
> seconds have been around long enough that any IT system which can't
> accommodate them is poorly designed.

You've clearly not dealt with many such system then if you are going
to make such sweeping statements.  It is *HARD* to design systems to
be perfect around leap seconds.  I'd grant you that most systems
likely operate correctly given that leap seconds exist, but I'm less
sure they all work perfectly when a leap second happens.  It has been
5 years since the last one and even well written systems haven't been
tested by fire.

Leap second complicate things in hundreds of little ways.  As someone
who has to write software that deals with leap seconds on a daily
basis, I can tell you it makes it more expensive to write and debug
and more prone to weird failure cases.  phk's point isn't that the IT
industry can cope.  It is that if they didn't have to cope, things
would be a lot cheaper.  He's right about that given the number of
hours that I see devoted to designing for leap seconds; arguing about
how, exactly, they work; understanding the subtle implications of such
simple rules; setting up expensive simulators to test the leap
seconds; etc, etc, etc.  The truth of the matter is that there's a
very real cost to leap seconds.


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