To: authorities responsible for the measurement and distribution of time
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 difference between UTC and the International Atomic Time TAI is:from 2015 July 1, 0h UTC, to 2017 January 1 0h UTC: UTC-TAI = - 36s
from 2017 January 1, 0h UTC, until further notice : UTC-TAI = - 37s
This means that tomorrow, 3:59:59 PM PST will be followed by 3:59:60 PM PST prior to the advent of 4:00:00 PM PST.
The leap second's stay of execution has been extended until at least 2023. Whew!