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Comment by speleo_engr | Hacker News Reader

Your article is about time zones, not leap seconds?

The US has put forth a proposal to abolish leap seconds. It is now supported by China, Australia, Japan, and South Korea. The ITU keeps punting on actually voting on it - it's now scheduled for 2023.

https://en.wikipedia.org/wiki/Leap_second

A day already drifts... every single day in fact. Why is 0.9 sec the magic threshold for maximum drift? Why can't it be 1 minute of drift, or 1 hour of drift? We are putting out problematic corrections for something a minor drift on the scale of years that should be happening on the scale of centuries or millennia in my opinion.

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That's interesting, I stand corrected. TIL that it's actually a heavily disputed topic and much less clear than I painted it, I had quite a different impression before — thanks!

Happy to see it is not just me that enjoy getting rid of my ignorance : )

It's a lot easier to test and prepare for something that occurs at least semi-regularly than a monumental event far into the future that is "so far into the future we don't have to worry about it"....

If we abolish leap seconds (and any other changes to UTC) and let the error accumulate until it hits 30 minutes then a 1-hour time zone change can adjust for it. Time zone changes happen at least semi-regularly so it wouldn't be monumental.

It would take millennia for such an error to accumulate. Leap seconds are inserted less than once a year and 30 minutes is 1800 seconds.

Falsehoods programmers believe about leap seconds: 1. The rate at which leap seconds are inserted will remain roughly constant. [...]

The Earth's rotation is slowing down (by about 2 ms per day per century), so the difference between TAI and UT1 is increasing quadratically, not linearly.

Wouldn’t that move the international date line?

I guess so, but I don't know why that matters.

The international date line isn't straight in order to avoid land. Moving it would be problematic.

think of it as ordinal: you're shifting left 1 unit, not moving the line, per se.

Still matters because some places want to make sure it's the same day (according to their local reckoning) as it is somewhere else in particular (usually a major trading partner).

Or the next town over.

The other boundaries are a lot straighter.

Imagine what would happen when the International Date Line ends up in the middle of the US.

1 minute of drift seems fine. 1 hour of drift is rather noticeable.

If the drift is about 0.5 second per year, about a minute of drift will have to be compensated on a century border.

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