[tz] Extra transition for Europe/London with 2023d

[Brooks Harris]

On 1/9/2024 4:45 PM, Doug Ewell wrote:
> Brooks Harris wrote:
>
>> The leap-second is evil.
> Presumably in the same way that leap year is “evil,” and for the same reason.
>
> --
> Doug Ewell, CC, ALB | Lakewood, CO, US | ewellic.org
Ah, no.

Ok, my comment was a bit smart aleck. The leap-second is "evil" for 
several reasons.

Leap-seconds are introduced at irregular times to maintain approximation 
of observed solar time. They are not algorithmically predicable, 
requiring lookup of the metadata provided by IERS.

Posix-time and many systems that have fixed 86400-second-days have no 
way to properly represent leap-seconds, positive or negative. You can't 
fit 86401 pegs in 86400 holes, nor fill all 86400 holes with 86399 pegs. 
This is the root of the great leap-second controversy, the 
incommensurability between UTC with leap-seconds and systems with fixed 
86400-second-days, which has been raging since at least 1999.

The leap year is algorithmically predicable and doesn't cause 
interoperability problems.

-Brooks