[LEAPSECS] Longer horizon

[Daniel R. Tobias]

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 
dangerous.

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.


-- 
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