[tz] No leap second on 2021-12-31

[Tony Finch]

Kerry Shetline via tz <tz at iana.org> wrote:

> What’s interesting is that the Earth is undergoing an odd span of time
> during which it has been spinning a bit faster instead of slowing down.
> If this keeps up, not only will it be a while until we see another leap
> second, but in a few years we might experience the first negative leap
> second, where a second is dropped from the end of the last minute just
> before 00:00 UTC.

Yes, it's super weird :-)

I have a program that uses the formula from IERS Bulletin A to guess when
the next leap second might happen and what direction it will be. Typically
(over the last 10 years) the length of day (ignoring seasonal variation)
has been about 1ms longer than 24*60*60 seconds. Five years ago (June
2016) the LoD peaked at nearly 1.5ms extra; at the moment it is about
0.25ms too short. If this continues, the next leap second will be a
negative leap second at the end of 2028.

https://github.com/fanf2/bulletin-a

Bulletin D announces the value of DUT1 to be used in radio time signals;
the most recent one at the end of last month was the first ever to
increase DUT1 (from -0.2s to -0.1s). Leap seconds are scheduled to prevent
DUT1 getting near +/- 1.

Tony.
-- 
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