Re: [LEAPSECS] ITU Meeting last year

From: Markus Kuhn <>
Date: Thu, 20 Jan 2005 12:17:30 +0000

matsakis.demetrios_at_USNO.NAVY.MIL wrote on 2005-01-19 20:19 UTC:
> A resolution was proposed to redefine UTC by replacing leap seconds by leap
> hours, effective at a specific date which I believe was something like 2020.

Thanks for the update!

Did the proposed resolution contain any detailed political provisions
that specify, who exactly would be in charge of declaring in about six
centuries time, when exactly the first UTC leap hour should take place?

Will IERS send out, twice a year, bulletins for the next *600 years*,
announcing just that UTC will continue as usual for the next 6 months?
Not the most interesting mailing list to be on ...

And when the day comes, will people still recognize the authority of
IERS and ITU in such matters? Keep in mind that the names, identities,
and structures of these instritutions will likely have changed several
times by then. Also keep in mind that any living memory of the last UTC
leap will then have been lost over twenty generations earlier. The
subject won't get any less obscure by making the event a 3600x more rare

If this proposal gets accepted, then someone will have to shoulder the
burden and take responsibility for a gigantic disruption in the
global^Wsolar IT infrastructure sometimes around 2600. I believe, the
worry about Y2K was nothing in comparison to the troubles caused by a
UTC leap hour. We certainly couldn't insert a leap hour into UTC today.

In my eyes, a UTC leap hour is an unrealistic phantasy.

Judging from how long it took to settle the last adjusting disruption of
that scope (the skipping of 10 leap days as part of the Gregorian
calendar reform), I would expect the UTC leap hour to become either very
messy, or to never happen at all. Who will be the equivalent of Pope
Gregory XIII at about 2600 and where would this person get the authority
from to break thoroughly what was meant to be an interrupt-free computer
time scale. Even the, at the time, almightly Catholic Church wasn't able
to implement the Gregorian transition smoothly by simply decreeing it.

Do we rely on some dictator vastly more powerful than a 16-th century
pope to be around near the years 2600, 3100, 3500, 3800, 4100, 4300,
etc. to get the then necessary UTC leap hour implemented?

Remember that UTC is used today widely in computers first of all because
it *lacks* the very troublesome DST leap hours of civilian time zones.
Most of the existing and proposed workarounds for leap seconds (e.g.,
smoothing out the phase jump by a small temporary frequency shift) are
entirely impractical for leap hours.

Please shoot down this leap-hour idea. The problem is not solved by
replacing frequent tiny disruptions with rare catastrophic ones. It is
hardly ethical to first accept that a regular correction is necessary,
but then to sweep it under the carpet for centuries, expecting the
resulting mess to be sorted out by our descendents two dozen generations
later on.

Leap hours are 3600 more disruptive than leap seconds!

If ITU wants to turn UTC into an interrupt-free physical time scale
decoupled from the rotation of the Earth, then it should say so
honestly, by defining that UTC will *never* ever leap in any way,
neither by a second, nor by an hour.


Markus Kuhn, Computer Lab, Univ of Cambridge, GB | __oo_O..O_oo__
Received on Thu Jan 20 2005 - 04:17:50 PST

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