[LEAPSECS] alternative to smearing

[Warner Losh]

On Wed, Jan 4, 2017 at 9:36 PM, Steve Summit <scs+ls at eskimo.com> wrote:
> Warner Losh wrote:
>> Steve Summit <scs+ls at eskimo.com> wrote:
>> > The requirement for tables (and, correspondingly, the
>> > "impossibility" of dealing with future UTC dates more than a few
>> > months out) depends on what you're trying to do...
>> > In particular, if right now it's 2017-01-05T01:56:13, I can
>> > obviously compute that (say) exactly three years from now is
>> > 2020-01-05T01:56:13, and I can even set a computer alarm to
>> > go off then, even if neither I nor the (suitably programmed)
>> > OS kernel that's tracking the alarm know in advance how many
>> > leap seconds there might end up being between now and then.
>>
>> Except that's not how things are programmed... People can talk
>> about it, but computers don't always store things that way. The
>> non-uniform radix presents problems. Trying to play semantic games
>> like this doesn't change that. There's problem, and trying to
>> equivocate away by saying "well, if you just did it right it would be
>> OK" isn't a helpful position. Requiring every computer to do
>> complicated things so that a leap second can work once in a blue moon
>> isn't a good engineering tradeoff.
>
> Indeed.  Did you see the message a few hours ago where I
> mentioned the "New Jersey approach" (aka "Worse is better")?
>
> But my point, my quibble with tvb's list, was that he said that
> some things were impossible or require leap second tables, when
> in fact they're merely difficult (to the point, depending on your
> engineering tradeoffs, of being a bad idea) or sometimes require
> leap second tables.
>
> I don't think that saying something is impossible, when it's
> merely difficult, is helpful either.

Saying something is impossible is just a short hand for "impossible to
implement efficiently" which is a decidedly helpful thing to say.
Forcing a design that can't be fast will inevitably result in a
competing design that is fast winning out, even in the face of
correctness. time_t is one such example: It made it easy to do local
time and literally impossible to do UTC.

Warner