The Wayback Machine - https://web.archive.org/web/20210302230704/https://www.ucolick.org/~sla/leapsecs/
UTC might be redefined without Leap Seconds
After over a decade of discussions the ITU-R and other groups
have not managed to come to a consensus on whether or not radio
broadcast time signals should continue to have leap seconds.
As seen in the following linked pages, a problem is that simply
omitting leap seconds would redefine the meaning of the word
"day" so that it is not related to the sun in the sky,
nor connected with the rotation of the earth.
In 1970 the CCIR (predecessor of the ITU-R) decided to
disconnect clocks from the rotation of the earth, but they kept
the calendar connected to the rotation of the earth.
That decision was implemented starting in 1972, and since
then the leap seconds have maintained the connection.
In 2015 the ITU-R decided not to decide whether the calendar
will also become disconnected from the rotation of the earth.
There is currently no open question about leap seconds at the
ITU-R, so they will take no further action until 2023.
The request from the ITU-R at WRC-15 was for a bunch of external
international agencies (none of which is involved in setting
standards for computing systems) to try to forge some agreement
which the ITU-R might be able to approve in 2023.
At least until that time leap seconds will continue.
There are basically two options available:
if UTC retains leap seconds
one calendar day counts one turn of the earth on its axis
with respect to the sun
if UTC abandons leap seconds
one calendar day counts
794 243 384 928 000 hyperfine
oscillations of cesium-133
One person who suggested the idea of leap seconds also
pointed out that leap seconds would cause problems for
automated systems.
Before the first leap second happened he explained that USNO
time systems would not use leap seconds.
These documents contain transcriptions from the 1955 meeting
where one second was redefined to have a duration which is
unrelated to the duration of one day.
From this point on time became split between the traditional
meaning that has always been in the calendar and the technical
meaning needed for precision systems.
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.
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.
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.
This document gives a picture of how the ITU-R has spent over
ten years on redefining UTC without coming to a conclusion.
It includes hundreds of links to almost all on-line material
pertaining to the future of leap seconds.
This is the document which was originally visible at this URL.
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.
Previously, the ITU-R convened a
Colloquium on the UTC Time Scale
in Torino Italy during 2003 May.
At the conclusion of that meeting the invited experts suggested
that a solution to the problems of leap seconds in the radio
broadcast time scale would be
to create a new atomic timescale named TI in about
the year 2022.
Subsequent to that meeting the delegates to the ITU-R seem to
have rejected or ignored the advice given to them by the experts
who attended their meeting.
Everything below here is old information.
Please focus on the links at the top of the page.
The information below remains here largely for the sake of URL permanence.
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:
The survey was performed on behalf of URSI Commission J, which is
Radio Astronomy.
The survey was performed before the nature of the cost
implications of discontinuing leap seconds had been considered.
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
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
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?
In 1970 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
English
leap second,
leap seconds
German
Schaltsekunde,
Schaltsekunden
French
seconde intercalaire,
secondes intercalaires
Spanish
segundo intercalar, segundos intercalares,
segundo intercalado, segundos intercalados,
segundo adicional, segundos adicionales,
segundo extra
(tal vez segundo bisiesto,
segundos bisiestos)
Italian
secondo intercalare,
secondi intercalari
Portuguese
segundo intercalado,
segundos intercalados
Swedish
skottsekund, skottsekunder
Icelandic
hlaupasekundum, hlaupasekundur
Danish
skudsekund, skudsekunder
Dutch
schrikkelseconde, schrikkelseconden
Russian
дополнительная секунда,
дополнительные секунды
Steve Allen <sla@ucolick.org>
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