Re: Proposal for a Smoothed Coordinated UniversalTime(UTS)

From: Markus Kuhn <>
Date: Mon, 30 Oct 2000 15:17:33 +0000

John Cowan wrote on 2000-10-25 20:23 UTC:
> Steve Allen wrote:
> > Of course this is pretty much the disease that most systems running
> > NTP currently have.


> Not at all. Systems with NTP make smooth adjustments, applicable to
> themselves alone, to a standard that uniformly ticks SI seconds.

That is also the clearly stated idea behind UTS: A standardized
interoperable way of making a smooth adjustment to UTC on systems where
displaying is not an option and where high-precision
time-interval measurements are anyway neither feasible nor necessary in
practice, because due to interrupt latencies, preemptive scheduling,
variable CPU clock speed, etc. <0.1% time-interval measurement errors
have anyway to be tolerated by applications.

You might want to read the extremely carefully worded proposal again if
this was not evident from a first quick browsing of the text.

> The proposal would make the very length of the SI second depend on the date!

No, UTS is definitely *NOT* changing the SI second! UTS just defines a
clock display behaviour, not a new physical unit of measurement. UTS can
be converted into UTC and vice versa (using a 1h leap second warning),
so no information is lost. Just like DST is not changing the length of
the SI second to -3599 seconds for one second every fall. Just like UTC
did not change the length of the SI second before 1972. Just like
interrupts delaying a return of gettimeofday() do not change the speed
of light or the meter.


Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at,  WWW: <>
Received on Mon Oct 30 2000 - 07:17:51 PST

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