World Radiocommunication Conference (WRC-15)
Geneva, 2–27 November 2015
INTERNATIONAL TELECOMMUNICATION UNION
CPG15(15)055 Annex V-24
[Addendum 14 to
Document 9-E]
17 June 2015
Original: English
PLENARY MEETING
European Common Proposals (CEPT)
PROPOSALS FOR THE WORK OF THE CONFERENCE
Agenda item 1.14
1.14
to consider the feasibility of achieving a continuous reference time-scale, whether by
the modification of coordinated universal time (UTC) or some other method, and take appropriate
action, in accordance with Resolution 653 (WRC-12);
Editor's Note 1:
OPTION A (France)
Introduction
In accordance with Resolution 653 (WRC-12) the required studies have concluded on four possible
methods to satisfy the agenda item in order to achieve a continuous time-scale. In the current
definition of Universal Coordinated Time (UTC) the time-scale is adjusted to the mean solar time
UT1 by inserting or removing a second whenever the difference between UTC and UT1 approaches
0.9 s. This extra second is known as the leap second.
Method A of the CPM report proposes to stop the leap second procedure in the definition of UTC,
this proposal is consistent with this particular method and in particular Method A1 when the
acronym UTC is kept.
Removing the leap second from the definition of UTC will allow the dissemination of a continuous
time-scale while removing the need to adjust UTC with the leap second with the associated risk of
errors that in the past led to mishaps in telecommunication and computer systems.
However since some systems such astronomical instruments rely on UT1 or its current
approximation UTC, software for these systems may need to be modified to be able to recover UT1
from UTC with a difference bigger than 0.9 s. It is then proposed to delay the suppression of the
leap second insertion by 5 years and implement the proposed modifications of the Radio Regulation
in 2021.
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ARTICLE 1
Terms and Definitions
Section I – General Terms
MOD
EUR/1.14/1
1.14
Coordinated Universal Time (UTC): Time-scale, based on the second (SI) and
maintained by the Bureau International des Poids et Mesures (BIPM), that forms the basis for the
coordinated dissemination of standard frequencies and time signals, as defined in
Recommendation ITU-R TF.460-6. (WRC-0315)
For most practical purposes associated with the Radio Regulations, UTC is equivalent to
mean solar time at the prime meridian (0° longitude), formerly expressed in GMT.
Reasons: To remove the incorporation by reference of Recommendation ITU-R TF.460-6, which
defines the use of leap seconds in UTC, add a reference to the international organization responsible
for the maintenance of the UTC time-scale, and remove the equivalence between UTC and the
mean solar time at the prime meridian.
ARTICLE 2
Nomenclature
Section II – Dates and times
MOD
EUR/1.14/2
2.5
Whenever a date is used in connection with Coordinated Universal Time (UTC), this
date shall beis that ofat the prime meridian at the appropriate time, the prime meridian
corresponding to zero degrees geographical longitude.
MOD
EUR/1.14/3
2.6
Whenever a specified time is used in international radiocommunication activities, UTC
shall be applied, unless otherwise indicated, and it shall be presented as a four-digit group
(0000-2359). The abbreviation UTC shall be used in all languages.
Reasons: Consequential changes resulting from the MOD to RR No. 1.14.
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MOD
EUR/1.14/4
CHAPTER X
Provisions for entry into force of the Radio Regulations
MOD
(WRC-1215)
EUR/1.14/5
ARTICLE 59
Entry into force and provisional application
of the Radio Regulations (WRC-1215)
MOD
EUR/1.14/6
59.1
These Regulations, which complement the provisions of the Constitution and
Convention of the International Telecommunication Union, and as revised and contained in the
Final Acts of WRC-95, WRC-97, WRC-2000, WRC-03, WRC-07, and WRC-12 and WRC-15,
shall be applied, pursuant to Article 54 of the Constitution, on the following basis. (WRC-1215)
ADD
EUR/1.14/7
59.13
The other provisions of these Regulations, as revised by WRC-15, shall enter into force
on 1 January 2017, with the following exceptions: (WRC-15)
ADD
EUR/1.14/8
59.14
The revised provisions for which other effective dates of application are stipulated in
Resolution:
[A114-UTC] (WRC-15) (WRC-15)
ADD
EUR/1.14/9
RESOLUTION [A114-UTC] (WRC-15)
Provisional application of certain provisions of the Radio Regulations
as revised by WRC-15 and abrogation of certain
Resolutions and Recommendations
The World Radiocommunication Conference (Geneva, 2015),
considering
a)
that this Conference has adopted modifications of Nos. 1.14, 2.5 and 2.6 regarding the
modification of UTC to achieve a continuous reference time-scale;
b)
that this Conference has, in accordance with its terms of reference adopted a partial
revision to the Radio Regulations, which will enter into force on 1 January 2017;
c)
date;
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that some of the provisions, as amended by this Conference, need to apply after that
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d)
that to ensure sufficient time for legacy systems to update hardware and/or software to
accommodate the stopping of insertion of leap seconds in UTC, Nos. 1.14, 2.5 and 2.6 need to
apply at a later stage;
resolves
1
that, as of 1 January 2021, Nos. 1.14, 2.5 and 2.6, as revised by WRC-15, shall apply.
Reasons: To ensure sufficient time for legacy systems to update hardware and/or software to
accommodate the stopping of insertion of leap seconds in UTC.
SUP
EUR/1.14/10
RESOLUTION 653 (WRC-12)
Future of the Coordinated Universal Time time-scale
Reasons: No need for Resolution 653 (WRC-12).
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Editor's Note 2:
OPTION B (G)
Introduction
In accordance with Resolution 653 (WRC-12) the required studies have concluded on four possible
methods to satisfy the agenda item in order to achieve a continuous time-scale. In the current
definition of Coordinated Universal Time (UTC) the time-scale is adjusted to the Earth rotation
time UT1 by inserting or removing a second whenever the difference between UTC and UT1
approaches 0.9 s. This extra second is known as a leap second.
Method C of the CPM report proposed to retain the current definition of UTC but to also authorize
use of the continuous timescale TAI, which can be readily derived from a broadcast of UTC by
using a difference offset integer seconds number, which is to be disseminated alongside UTC where
practicable and by other methods. This proposal is consistent with this particular method and in
particular Method C1.
Authorising the use of TAI allows users to choose the most appropriate time-scale for their
application with the minimum of disruption and cost to existing activities and systems.
The proposed method (C1 of the CPM text) will recognise TAI as the only continuous time scale
recommended for purposes where leap second adjustments are undesirable, and will avoid
proliferation of multiple continuous time scales. UTC would remain the basis for civil timekeeping
worldwide, with time zone offsets as required.
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ARTICLE 1
Terms and Definitions
Section I – General Terms
NOC
EUR/XX/1
1.14
Coordinated Universal Time (UTC): Time-scale, based on the second (SI), as defined in
Recommendation ITU-R TF.460-6. (WRC-03)
For most practical purposes associated with the Radio Regulations, UTC is equivalent
to mean solar time at the prime meridian (0° longitude), formerly expressed in GMT.
MOD
EUR/XX/2
RESOLUTION 653 (WRC-15)
Future of the Coordinated Universal Time time-scale
The World Radiocommunication Conference (Geneva, 2015),
considering
a)
that the procedures for maintaining the Coordinated Universal Time (UTC) time-scale
are described by Recommendation ITU-R TF.460-6;
b)
that UTC is the legal basis for time-keeping for most countries in the world, and de
facto is the time-scale used in most others;
c)
that Recommendation ITU-R TF.460-6 states that all standard-frequency and time
signal emissions should conform as closely as possible to UTC;
d)
that Recommendation ITU-R TF.460-6 describes the procedure for the occasional
insertion of leap seconds into UTC to ensure that it does not differ by more than 0.9 seconds from
the time determined by the rotation of the Earth (UT1);
e)
that the occasional insertion of leap seconds into UTC may create difficulties for
systems and applications that depend on accurate timing;
f)
that a proliferation of many alternative continuous time-scales would lead to confusion
and that there is a need for only one to be recognized by the ITU
g)
that ITU-R studies resulted in no consensus on the proposal to discontinue leap seconds,
recognizing
a)
that some organizations involved with space activities, global navigation satellite
systems, metrology, telecommunications, network synchronization and electric power distribution
have requested a continuous time-scale;
b)
that for local time-of-day and for other specialized systems, there is a need for a
timescale reckoned with respect to the rotation of the Earth, such as the mean solar time at the
prime meridian, formerly known as GMT;
c)
that a change in the reference time-scale may have operational and therefore economic
consequences,
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noting
a)
that No. 1.14 defines UTC as a time-scale based on the second (SI), as defined in
Recommendation ITU-R TF.460-6;
b)
that modification of the definition of UTC may have consequential changes to Nos.
1.14, 2.5, 2.6 and some other provisions,
resolves
TAI is an acceptable alternative for those requiring a continuous time-scale and that it can be
derived from UTC using a difference offset integer seconds number.
invites ITU-R
To study how TAI can be derived from disseminated UTC and reflect this through appropriate
amendments to ITU-R TF.460.
instructs the Director of the Radiocommunication Bureau
to bring this Resolution to the attention of ITU-R, ITU-T, and ITU-D
instructs the Secretary-General
to bring this Resolution to the attention of relevant organizations such as the International Maritime
Organization (IMO), the International Civil Aviation Organization (ICAO), the General Conference
of Weights and Measures (CGPM), the Consultative Committee for Time and Frequency (CCTF),
the Bureau International des Poids et Mesures (BIPM), the International Earth Rotation and
Reference Systems Service (IERS), the International Union of Geodesy and Geophysics (IUGG),
the International Union of Radio Science (URSI), the International Organization for Standardization
(ISO), the World Meteorological Organization (WMO) and the International Astronomical Union
(IAU).
Reasons: To fulfil the requirement for continuous time scale.
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Editor's Note 3:
OPTION C (Russian Federation)
Introduction
In accordance with Resolution 653 (WRC-15) the required studies have been conducted. As
specified in Resolution 653 (WRC-15) «invites ITU-R 2» the mentioned studies cover technical and
operational issues related to possible implementation of a continuous reference time-scale. The
studies also considered disadvantages of such transition and its consequences regarding the effect
on operation of the existing telecommunication systems and their development.
Based on the obtained study results, another method to satisfy the AI is proposed. It implies keeping
without changes both the current definition of the Coordinated Universal Time (UTC) as contained
in Recommendation ITU-R TF.460-6 and the existing provisions of current Radio Regulations No.
1.14, suppression of Resolution 653 (WRC-12). This approach does not exclude the possibility to
introduce in Recommendation ITU-R TF.460-6 additional definitions and modifications and/or
materials in relation to continuous time scales in order to apply them for radiocommunication
systems where it is required.
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ARTICLE 1
Terms and Definitions
Section I – General Terms
NOC
EUR/XX/1
1.14
Coordinated Universal Time (UTC): Time scale, based on the second (SI), as defined
in Recommendation ITU-R TF.460-6. (WRC-03)
For most practical purposes associated with the Radio Regulations, UTC is equivalent
to mean solar time at the prime meridian (0° longitude), formerly expressed in GMT.
Reasons: No change in definition of UTC as specified in RR No. 1.14 and in Recommendation
ITU-R TF.460-6.
SUP
EUR/XX/2
RESOLUTION 653 (WRC-12)
Future of the Coordinated Universal Time time-scale
Reasons: Resolution 653 (WRC-12) is not needed.
MOD
EUR/XX/3
PRELIMINARY DRAFT REVISION
OF RECOMMENDATION ITU-R TF.460-6*1
Standard-frequency and time-signal emissions
(Question ITU-R 102/7)
(1970-1974-1978-1982-1986-1997-2002)
Scope
This Recommendation defines the implementation of Coordinated Universal Time (UTC) with the
procedure for adjustment of UTC by insertion of leap seconds and includes additional materials
with respect to the feasibility of using continuous system time-scales for radiocommunication
systems.
_______________
*
This Recommendation should be brought to the attention of the International Maritime
Organization (IMO), the International Civil Aviation Organization (ICAO), the General Conference
of Weights and Measures (CGPM), the Consultative Committee for Time and Frequency (CCTF),
the Bureau International des Poids et Mesures (BIPM), the International Earth Rotation and
Reference Systems Service (IERS), the International Union of Geodesy and Geophysics (IUGG),
the International Union of Radio Science (URSI), the International Organization for Standardization
(ISO) and the International Astronomical Union (IAU).
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The ITU Radiocommunication Assembly,
considering
a)
that the World Administrative Radio Conference, Geneva, 1979, allocated the
frequencies 20 kHz  0.05 kHz, 2.5 MHz  5 kHz (2.5 MHz  2 kHz in Region 1), 5 MHz  5 kHz,
10 MHz  5 kHz, 15 MHz  10 kHz, 20 MHz  10 kHz and 25 MHz  10 kHz to the
standard-frequency and time-signal service;
b)
bands;
that additional standard frequencies and time signals are emitted in other frequency
c)
the provisions of Article 26 of the Radio Regulations;
d)
the continuing need for close cooperation between Radiocommunication Study Group 7
and the International Maritime Organization (IMO), the International Civil Aviation Organization
(ICAO), the General Conference of Weights and Measures (CGPM), the Consultative Committee
for Time and Frequency (CCTF), the Bureau International des Poids et Mesures (BIPM), the
International Earth Rotation and Reference Systems Service (IERS) and the concerned Unions
of the International Council of Scientific Unions (ICSU);
e)
the importance of maintaining worldwide coordination of standard-frequency and
time-signal emissions;
f)
the need to disseminate standard frequencies and time signals in conformity with the
SI (International System of Units) second as defined by the CGPM;
g)
the continuing need to make universal time (UT) immediately available to an
uncertainty
of one-tenth of a second,
h)
that in 1975 the CGPM recommended the use of UTC as the basis of civil time;
i)
that other scientific organizations, particularly the International Astronomical Union
(IAU) and the International Union of Radio Science (URSI) have recommended the general use of
UTC;
j)
the importance of monitoring the difference between the UTC time scale and the time
defined by the rotation of the Earth (UT1) and maintaining the respective knowledge-base;
k)
that the IERS provides updated daily data relating the UT1 to UTC to users,
noting
that Recommendation ITU-R TF.460-6 is incorporated by reference in the Radio Regulations, and
that the revised Recommendation ITU-R TF.460 will become effective only after the date of entry
into force established by the appropriate World Radiocommunication Conference,
recognizing
1
that the World Administrative Radio Conference (Geneva, 1979) (WARC-79) has
decided that UTC shall be used in all international radiocommunication activities;
2
that according to Recommendation ITU-R TF.536 and in accordance with the
recommendation of the CGPM the designation of UTC is to be used in all languages;
3
that the UTC system with leap seconds was essentially introduced to provide a common
standard for broadcast time and frequency signals generated from the UTC(k) physical
representations;
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4
that some radiocommunication systems and particularly global navigation satellite
systems (GNSS) reproduce internal timescales for synchronization and special tasks. Such time
scales may be continuous and not conform to UTC;
5
that many radiocommunication systems use GNSS signals for synchronization tasks,
recommends
1
that all standard-frequency and time-signal emissions conform as closely as possible to
coordinated universal time (UTC) (see Annex 1); that the time signals should not deviate from UTC
by more than 1 ms; that the standard frequencies should not deviate by more than 1 part in 1010, and
that the time signals emitted from each transmitting station should bear a known relation to the
phase of the carrier;
2
that standard-frequency and time-signal emissions, and other time-signal emissions
intended for scientific applications (with the possible exception of those dedicated to special
systems) should contain information on UT1  UTC and TAI  UTC (see Annex 1);
3
that in case when radio systems reproduce time-scale which not conforms to UTC, and
disseminate signals, such signals should contain information on difference between reproduced time
scale and UTC.
ANNEX 1
Time and Time scales
Further no change
Reasons: In implementation of Method C2 amendments to Recommendation ITU-R TF.460-6 are
proposed to include additional definitions, corrections and/or materials with respect to the
feasibility of using continuous system time-scales for radiocommunication systems and also to be
aligned with UTC.
__________________
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