[tz] negative leap second predicted

[Brian Inglis]

On 2021-03-07 08:18, John Sauter via tz wrote:
> On Sat, 2021-03-06 at 17:27 -0800, Steve Allen via tz wrote:
>> On Sat 2021-03-06T15:54:42-0800 Guy Harris via tz hath writ:
>>> After all, we don't truncate the files at the date/time when they're 
>>> generated, given that we have no guarantee that there will be no changes
>>> in the future to the offset from UTC, or the DST rules, for a given tzdb
>>> region....

>> The way the crust is rotating now it is likely that jurisdiction(s)
>> will change time zone rule(s) before there is another leap second.

Or drop leap seconds and declare UTC is GMST.

> The way the crust is rotating now there will be a negative leap second
> on June 30, 2031.

There's a reason nobody is willing to commit to a prediction more than six 
months in advance. Even then they are not always as expected six months later - 
the last leap second could have been skipped, as dUT1 did not reach the value 
expected which would require a change. So it will be a longer than expected 
interval until the next.

However there is evidence of mutual interactions between earth rotation and 
seismic activity - braking increases earthquakes which foreshadows eruptions.

https://www.volcanodiscovery.com/volcano-activity/news/123478/Volcanic-activity-worldwide-4-Mar-2021-Etna-volcano-Pacaya-Fuego-Popocatepetl-Dukono-Krisuv.html

https://www.livescience.com/iceland-earthquakes-volcanic-eruption-2021.html

Significant earthquakes may make the distribution of the earth's mass more 
compact, decrease its moment of inertia and LoD, and increase rotation speed as 
angular momentum is conserved; significant eruptions which move large masses 
from the interior to the exterior may have the opposite effect.

There may also be effects due to resonance of tidal and natural ocean frequencies.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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