On 2020-11-16, at 11:44:07, Michael H Deckers via tz <tz@iana.org> wrote:
A positive leap second is usually taken to be a (left closed and right open) interval of length 1 s of TAI values that are not associated with UTC values by the function from UTC to TAI as published by the IERS. For the latest leap second this interval was [2017-01-01T00:00:36..2017-01-01T00:00:37[; while TAI was in that interval, UTC could be 36 s or 37 s less than TAI, and ITU recommends the use of their leap second notation for the value of UTC.
Is that the same as?: https://datacenter.iers.org/data/16/bulletinc-052.txt A positive leap second will be introduced at the end of December 2016. The sequence of dates of the UTC second markers will be: 2016 December 31, 23h 59m 59s 2016 December 31, 23h 59m 60s 2017 January 1, 0h 0m 0s The UTC "23:59:60" is extraordinary; I'd call it the "leap second". A "negative leap second" is problematic. It would be a TAI second with no matching UTC second. -- gil