Re: [Ntp] Leap smearing

Martin Burnicki <> Thu, 10 December 2020 14:33 UTC

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To: Magnus Danielson <>,
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From: Martin Burnicki <>
Organization: Meinberg Funkuhren GmbH & Co. KG, Bad Pyrmont, Germany
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Date: Thu, 10 Dec 2020 15:32:55 +0100
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Subject: Re: [Ntp] Leap smearing
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Magnus Danielson wrote:
> On 2020-12-10 01:24, Doug Arnold wrote:
>> Note it would always be possible to determine the unsmeared UTC if
>> needed in this approach.
> Yes, I think this should be done on the client side.

Again, IMO you have to distinguish.

If you have a "sophisticated" client for a specific application, you can
retrieve normal UTC from the server, with leap second warnings included,
and do the smearing locally at the client side.

As far as I know, some frameworks use UTC-SLS to do this, even if the
operating system time doesn't.

This should work fine for a specific application, but it would be
interesting to see what happens if programs that have been built with
UTC-SLS share timestamped data with programs that rely on the system
time provided by the native API calls of the operating system. ;-)

However, if you have "normal" clients and you just want to prevent your
applications from hickups when the system time is stepped back, it's
easier to let the server smear the time, because you only have to
configure this once, and all clients behave the same.

Martin Burnicki

Senior Software Engineer

MEINBERG Funkuhren GmbH & Co. KG
Phone: +49 5281 9309-414

Lange Wand 9, 31812 Bad Pyrmont, Germany
Amtsgericht Hannover 17HRA 100322
Geschäftsführer/Managing Directors: Günter Meinberg, Werner Meinberg,
Andre Hartmann, Heiko Gerstung