[LEAPSECS] Longer horizon

Daniel R. Tobias dan at tobias.name
Tue Jul 10 19:37:57 EDT 2012

On 10 Jul 2012 at 8:38, Warner Losh wrote:

> You really don't understand the depth of the leap second issue in

> software. If it were that easy, it would have actually been

> solved. People just don't care, and that's the problem.

Actually, from what I've seen and heard about this year's crop of
bugs, server crashes, etc., relating to the leap second, the big
problems come when the developers know and care just enough to be

If you take the total dumbass approach to leap seconds, like you
don't even know they exist, or pretend they don't exist even though
you've heard of them, then in most cases your hardware and software
will muddle through just fine. It might wind up a second off after
the leap second happens, but that will just be an additional
one-second delta added (or subtracted) on to whatever other delta
might exist due to normal clock drift, which will eventually get
corrected (either in an abrupt jump or smoothed out, depending on the
system software) when the system next polls whatever external time
source it periodically syncs to (if it does this at all). Or maybe
the end user will just once in a while set the clock manually to the
top of the hour when the theme song to his favorite sitcom comes on
the boob tube. At any rate, it will eventually take the leap second
into account, and nothing will crash and burn in the meantime.

It's only when you actually attempt to get the system to account for
the leap second immediately and precisely when it happens that you
end up having to code in something convoluted that only runs every
couple of years, with all the potential to screw it up and cause a
major crash of some sort. Probably only less than 1/10 of 1 percent
of systems actually need this degree of precision, so the other 99.9%
are best off not even trying to do anything special for the leap
second, though some defensive programming to keep from crashing if
fed something like "23:59:60" from a remote site would be desirable.

== Dan ==
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