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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

Three pictures that show the reasons for leap seconds

A brief and pictorial page showing how our clocksare affected by leap seconds, and why there is noschedule for them.

time scales have a choice between three goals

A time scale can pick two of three.
But which two? A look at where the decision processes went wrong.

timing systems that always refused to use leap seconds

One person who suggested the idea of leap seconds alsopointed out that leap seconds would cause problems forautomated systems.Before the first leap second happened he explained that USNOtime systems would not use leap seconds.

When the second became unrelated to the day

These documents contain transcriptions from the 1955 meetingwhere one second was redefined to have a duration which isunrelated to the duration of one day.From this point on time became split between the traditionalmeaning that has always been in the calendar and the technicalmeaning needed for precision systems.

Elapsed time

A javascript program showing the international problem thatPOSIX is not currently capable of providing an interface thatproperly describes time, and that international agreementsconfound the process of fixing that problem.

correct precision handling of leap seconds using code already on POSIX systems

A prescription that shows how existing deployed and testedcode could allow computing and telecommunications systems tohandle leap seconds without difficulty, but only if the ITU-Rchanges the name of the broadcast time scale.

Differences between time scales over 4000 years

Plots showing how time keeping got the way it is, andsuggesting a way to reduce the issues associated withleap seconds which is compatible with human history aswell as modern systems for navigation, telecomms, and POSIX.

Differences between time scales at year 2100

Plots with estimates of how far off the calendar and clockmight drift by the year 2100 if leap seconds are abandoned inthe year 2020.

calendar of events and gathering of references

This document gives a picture of how the ITU-R has spent overten years on redefining UTC without coming to a conclusion.It includes hundreds of links to almost all on-line materialpertaining to the future of leap seconds.This is the document which was originally visible at this URL.

Figures and tables showing the need for leap seconds

These include plots of how the rotation of the earth slowsdownand speeds up, and other material on theproposed changes.

A brief history of time scales

During the past century or so the concept of time has changedconsiderably. The results of struggling with ever more refinednotions of time have been some two dozen new ways of expressingtime.

Two kinds of time are necessary

In 1954 D.H. Sadler described the need and implicationof two kinds of time.His monograph is clearer than any other writeup for the next60 years.

What could happen if civil time becomes atomic time?

This question was treated at the meeting Requirements for UTC and Civil Timekeeping on Earth held during 2013 May in Charlottesville VA USA. Thepresentations at that meeting resulted in 350 pages of proceedings (also available onCDROM).

Previously this question was treated at the meeting Decoupling Civil Timekeeping from Earth Rotation held during 2011 October in Exton PA USA. Thepresentations at that meeting resulted in 400 pages of proceedings (also available onCDROM).

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 isRadio Astronomy.
• The survey was performed before the nature of the costimplications of discontinuing leap seconds had been considered.
• The survey was performed before it had become clear that those whowere suggesting changes to UTC were either serious or capable ofdoing 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

A description of costs and consequences

This is an introduction to the survey below.

The survey about schedule and cost

This is an attempt to gather some estimates of the scheduledtime and costs which observatories will have to expend if leapseconds are discontinued.

The results of the survey

Here are the data gathered in response to the above survey.The results are sparse. This may be because it is difficultto answer the questions without expending most of the effortrequired to identify the deficiencies, and this is amplifiedby the absence of a clear indication of the detailed nature ofa change.

Various postings that I have made to the LEAPSECS mailing list

UTC vis-a-vis civil time (2003-02-12) local text/plain, Mail Archive, LEAPSECS subscribers

UTC without leap seconds would deviate from all other forms of"universal" time.

legal time (2003-04-10) local text/plain, LEAPSECS subscribers,(ideas included here)

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?

UTC is doomed (2003-04-22) local text/plain, LEAPSECS subscribers,(ideas included here)

But it is not doomed anytime soon.

UT and the IAU (2003-05-10) local text/plain, LEAPSECS subscribers,(ideas includedhere,here, andhere)

Universal Time was defined and approved by action of the IAU

will history repeat itself? (2003-05-10) local text/plain, LEAPSECS subscribers,(ideas included here)

In 1970 the CCIR (predecessor of the ITU) was in a similarposition with respect to UTC. Rather than create an international andinterdisciplinary committee to choose a solution, the CCIR actedunilaterally and imposed a solution on the world with less than 2years notice.

Polyglot search engine bait

English

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German

Schaltsekunde,Schaltsekunden

French

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Spanish

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Italian

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Portuguese

segundo intercalado,segundos intercalados

Swedish

skottsekund, skottsekunder

Icelandic

hlaupasekundum, hlaupasekundur

Danish

skudsekund, skudsekunder

Dutch

schrikkelseconde, schrikkelseconden

Russian

дополнительная секунда,дополнительные секунды