Joe Touch <touch@xxxxxxx> wrote: > > Smearing leads to differing interpretations of elapsed time for two reasons: > > 1) smearing isn't unambiguously specified > 2) smearing doesn't match the clock standards set by the ITU (who > defines UTC) Since leap smear is becoming more popular, it would be sensible to try to get a consensus on the best way to do it if you do it. Clearly organizations that do leap smear think (2) leap seconds are too much trouble so it's better to diverge from official time in a controlled manner. To clear up (1) there are a few technical choices on which people seem to be working towards some kind of agreement... * If you centre the smear period over the leap second, your maximum error from UTC is 0.5s, which seems to be preferable to starting or ending the smear period on the leap second * Linear smear works better than sigmoid smear, since it minimizes the rate divergence for a given smear period, and NTP's algorithms react better * Longer smear periods are better, because they give NTP more time to react to the rate change, and they minimize the rate difference It looks to me like a 24h leap smear from 12:00 UTC before the leap to 12:00 UTC after the leap has a good chance of becoming more popular than other leap smear models. Tony. -- f.anthony.n.finch <dot@xxxxxxxx> http://dotat.at/ - I xn--zr8h punycode Humber, Thames: West 5 to 7, veering northwest 6 to gale 8, perhaps severe gale 9 later in Humber. Moderate or rough, occasionally very rough, becoming high at times later in Humber. Rain then showers. Moderate or good.