[LEAPSECS] Consensus building 2

[Tim Shepard]

> * definition: UTC-1972-day - a duration either 86400 SI-seconds or

> 86401 SI-seconds long


or 85999


> * leap-seconds are added to UTC-1972 with the aim of keeping UT1 and

> UTC no more than 0.9 SI-seconds apart


Leap seconds may be inserted or deleted, though so far there have only
been insertions, and the way things are going there are unlikely to
ever be any deletions.