[LEAPSECS] alternative to smearing

[Brooks Harris]

On 2017-01-05 06:26 AM, Hal Murray wrote:
> [do something N years in the future]
>> Except that's not how things are programmed. Programming it that way would
>> be very inefficient in a part of the kernel that has to be ultra-efficient.
>> Since you don't know how many seconds it will from now, you can't schedule a
>> timeout. The current setup of UTC doesn't let me know how many seconds it
>> will be in the future. People can talk about it, but computers don't always
>> store things that way. ...
> Are there any performance critical chunks of code that want to wait until N
> years from now?  I doubt it.
>
> If I ask for 6 months rather than a few years, then you also have to consider
> daylight savings.  Actually, you have to consider it anyway.  Congress might
> change the start/stop times again and your wait-until might hit one of them.
>
> I think that means that if you want to schedule something a long time in the
> future specified as date and time rather than seconds from now, you have to
> wakeup a bit early and recompute how long to wait.  For leap seconds, the bit
> early has to be a few months, depending on how long it takes you to update
> your leap file.  For daylight savings, I don't think you can predict a value
> of a bit early.  Congress isn't dependable.
>
> How far in advance were the last daylight savings changes announced?
>
>

Roughly a year and a half or so, I think. I haven't researched when the 
announcement might have officially been made by the Dept of Commerce, 
who, I believe, would have been responsible for that:

Daylight saving time in the United States >> Second extension (2005)
https://en.wikipedia.org/wiki/Daylight_saving_time_in_the_United_States

"By the Energy Policy Act of 2005, daylight saving time (DST) was 
extended in the United States beginning in 2007.[9]"

"... Wyoming Senator Michael Enzi and Michigan Representative Fred Upton 
advocated the extension from October into November especially to allow 
children to go trick-or-treating in more daylight."

Energy Policy Act of 2005
https://en.wikipedia.org/wiki/Energy_Policy_Act_of_2005

"The Energy Policy Act of (Pub.L. 109–58) is a bill passed by the United 
States Congress on July 29, 2005, and signed into law by President 
George W. Bush on August 8, 2005,..."

I'd put that is a category of "reasonable notice of change", but not all 
jurisdictions are so responsible.

[More generally I'd put the whole notion of Daylight Savings Time in the 
category of "stupid", but there's no fighting city hall....]

-Brooks