On 2016-12-05 04:04, Tony Finch wrote:
Paul Eggert <eggert@cs.ucla.edu> wrote:
With leap smearing, the ideal clock is at most 0.5 s off UTC, as opposed to being at most 1.0 s off with strict POSIX time.
It's a bit more complicated than that :-)
There are a number of variations of leap smear. The ones that centre the smear interval on the leap second have an up-to-0.5s divergence from UTC. The ones that have the whole smear interval before (or after) the leap second have an up-to-1s divergence from UTC.
If I understand the ntpd documentation, they have implemented a configurable smear interval that occurs before the leap second.
Note their provisos not to provide smear on public servers - to avoid legal issues; NTP must be rebuilt to support smear and be configured with a leap file and smear interval; server and peer times are still UTC, only client packets are fudged with the current offset, and they contain a refid address of 254. followed by 2 integer bits and 22 fractional bits of the signed (negative) offset from 0..-1s, calculated using the Google cosine formula. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada