[tz] negative leap second predicted

Andrew Gierth andrew at tao11.riddles.org.uk
Sun Mar 7 18:03:55 UTC 2021

>>>>> "John" == John Sauter via tz <tz at iana.org> writes:

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

The lack of any leap second (positive or negative) on Jun 30 2031 has
already been formally announced:


  "NO leap second will be introduced at the end of June 2021.
   The difference between Coordinated Universal Time UTC and the
   International Atomic Time TAI is :
     from 2017 January 1, 0h UTC, until further notice : UTC-TAI = -37 s"

IMO, a negative leap second would not be introduced until it became
absolutely necessary (assuming we don't abolish leap seconds first),
considering the likely disruption that it would cause. That being the
case, there is about 800ms of slack available, and the predictions I've
seen are for 2021 to run short by only on the order of 20ms, so it would
take around 40 years before a negative leap second was required if the
current rotation is maintained, or about 8 years if the speedup
increases approximately linearly.


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