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

[Doug Ewell]

Brooks Harris wrote:

> 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.

That’s because the earth doesn’t jiggle and joggle uniformly. If it had instead been decided to introduce leap seconds on a regular, predictable 18- or 24-month cycle, based on the data we had in the early 1970s, we would be faced with inaccuracy in the opposite direction.

> 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.

You also can’t fit an earth year into a perpetual, integral number of 7-day weeks, or into 12 or 13 months of uniform length. The fallacy is in trying to fit those pegs into those holes at all.

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

For the next several thousand years, anyway, which is not our problem or that of our children, any more than the inaccuracy of the Julian calendar was many hundreds of years removed from being Caesar’s problem.

Apologies for snarkiness.

--
Doug Ewell, CC, ALB | Lakewood, CO, US | ewellic.org