[LEAPSECS] Bloomberg announced its smear

Martin Burnicki martin.burnicki at burnicki.net
Thu Sep 29 03:18:11 EDT 2016


Tom Van Baak wrote:
>> Hm, IMO the advantage of the initial smear approach (24 hours before the
>> leap second) is that smearing is finished as soon as the leap second has
>> occurred, so the beginning of the next UTC day /hour / minute is accurate.
> Martin,
> I suspect your idea only works in cases when the time server is
> instantaneously jamming time to a stateless client. But there is
> often some level of filtering and so the client will necessarily lag
> the server. In this case the client will not have accurate UTC until
> many time constants after midnight.

First please note I've implemented this in ntpd, but it's not my idea.
It's what Google did when they first smeared time.

IMO the advantage of the cosine approach is that smearing starts slowly,
then increases, and then fades out quite some time before it ends, so
the last samples during the smear interval should pretty much be in
coincidence with real UTC after the leap second. See the measurement
graphs in my PDF.


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