UTC might be redefined without Leap Seconds
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Three pictures that show the situation
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A brief and pictorial page showing how our clocks
are affected by leap seconds.
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Elapsed time
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A javascript program showing the international problem that
POSIX is not currently capable of providing an interface that
properly describes time, and that international agreements
confound the process of fixing that problem.
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How the problems could be solved now
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A prescription that shows how existing deployed and tested
code could allow computing and telecommunications systems to
handle leap seconds without difficulty, but only if the ITU-R
changes the name of the broadcast time scale.
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Differences between time scales
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Plots showing how time keeping got the way it is, and
suggesting a way to reduce the issues associated with
leap seconds which is compatible with human history as
well as modern systems for navigation, telecomms, and POSIX.
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A bibliographic gathering of references
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This is the document which was originally visible at this URL.
It includes hundreds of links to almost all on-line material
pertaining to the future of leap seconds.
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Figures and tables showing the reasons for leap seconds
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This includes some material on the proposed changes.
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A brief history of time scales
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During the past century or so the concept of time has changed
considerably. The results of struggling with ever more refined
notions of time have been some two dozen new ways of expressing
time.
What could happen if civil time becomes atomic time?
The colloquium in Torino resulted in a suggestion that a new atomic
timescale named TI might be created in about the year 2022. I have a
document with tables showing how roughly
when the difference will reach certain
sizes. I also consider what could happen to societies whether or
not civil time is changed from Universal Time (mean solar time, or
time-of-day) to atomic time. If leap hours were to be instituted they
might prove far more annoying
than leap seconds.
Optical and Infrared Observatories
Study of the bibliography above indicates that no formal survey has
ever been performed specifically to ask optical and infrared
observatories to consider the schedule and cost implications of
discontinuing leap seconds from UTC. The initial URSI survey was
published very broadly, and attempts were made to contact
observatories. Nevertheless, I believe that this survey was
inadequate for several reasons:
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The survey was performed on behalf of URSI Commission J, which is
Radio Astronomy.
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The survey was performed before the nature of the cost implications of
discontinuing leap seconds had been considered.
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The survey was performed before it had become clear that those
who were suggesting changes to UTC were either serious or
capable of doing it.
Some older optical and infrared telescopes were built or designed
before Stoyko had confirmed that the length of day varied
seasonally. Others were not designed to require pointing accuracy of
1 second of time. Often this was because they are manually pointed by
a full-time telescope technician -- not by the observer, not by
software. Telescopes such as these have never required their control
systems to distinguish between UT1 and UTC. Discontinuing leap seconds
requires a fundamental change in their operational procedures.
Astronomers should note in particular that the agenda for the meeting
in Torino considered financial aspects (costs and opportunities) for
several disciplines, but not for astronomy.
A survey of schedule and cost consequences for observatories
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A description of costs and consequences
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This is an introduction to the survey below.
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The survey about schedule and cost
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This is an attempt to gather some estimates of the scheduled
time and costs which observatories will have to expend if leap
seconds are discontinued.
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The results of the survey
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Here are the data gathered in response to the above survey.
The results are sparse. This may be because it is difficult
to answer the questions without expending most of the effort
required to identify the deficiencies, and this is amplified
by the absence of a clear indication of the detailed nature of
a change.
Various postings that I have made to the
LEAPSECS mailing list
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UTC vis-a-vis civil time (2003-02-12)
local text/plain,
Mail Archive,
LEAPSECS subscribers
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UTC without leap seconds would deviate from all other forms of
``universal'' time.
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legal time (2003-04-10)
local text/plain ,
LEAPSECS subscribers,
(ideas included here)
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If UTC switches to leap hours, how far in the future will those occur?
Under the current legal time for the US and UK (which is, effectively,
UT2) will lawsuits begin to happen when DUT1 exceeds a few seconds?
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UTC is doomed (2003-04-22)
local text/plain ,
LEAPSECS subscribers,
(ideas included here)
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But it is not doomed anytime soon.
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UT and the IAU (2003-05-10)
local text/plain ,
LEAPSECS subscribers,
(ideas included here, here, and here)
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Universal Time was defined and approved by action of the IAU
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will history repeat itself? (2003-05-10)
local text/plain ,
LEAPSECS subscribers,
(ideas included here)
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33 years ago the CCIR (predecessor of the ITU) was in a similar
position with respect to UTC. Rather than create an international and
interdisciplinary committee to choose a solution, the CCIR acted
unilaterally and imposed a solution on the world with less than 2
years notice.
Polyglot search engine bait
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English
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leap second,
leap seconds
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German
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Schaltsekunde,
Schaltsekunden
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French
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seconde intercalaire,
secondes intercalaires
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Spanish
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segundo intercalar, segundos intercalares,
segundo intercalado, segundos intercalados,
segundo adicional, segundos adicionales,
segundo extra
(tal vez segundo bisiesto,
segundos bisiestos)
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Italian
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secondo intercalare,
secondi intercalari
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Portuguese
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segundo intercalado,
segundos intercalados
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Swedish
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skottsekund, skottsekunder
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Icelandic
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hlaupasekundum, hlaupasekundur
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Danish
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skudsekund, skudsekunder
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Dutch
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schrikkelseconde, schrikkelseconden
Steve Allen <sla@ucolick.org>
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