The following e-mail message was published using the same distribution mechanisms as IERS Bulletins C and D just after IERS Bulletin C # 30 which announced the leap second on 2005-12-31.

Following the letter I have included a list of links to relevant documents and agencies mentioned therein.

From: "" <>
Subject: Note to IERS Users

July 2005
Letter to IERS Bulletins C and D users

Dear colleague,

As you are probably aware, international discussions are in progress on a
redefinition of UTC, including a possible suppression of the leap seconds

To reply to the request of several international organizations on a possible
evolution of UTC the International Telecommunication Union, ITU decided in
October 2000 the creation of a Working Group called "Special Rapporteur
Group", SRG chaired by Mr Ron Beard of the Naval Research Laboratory (NRL-
USA), in charge of studying by a large consultation the different possible
solutions. The SRG reports its conclusions to the ITU working party WP-7A.

The Special Rapporteur Group (SRG) organized a colloquium in Torino, Italy in
May 2003. No general agreement emerged from this colloquium.

In parallel, the US delegation to the WP-7A submitted, at the last meeting in
Geneva in October 2004, a proposal which contained the following items:

1 - Maintenance of a time scale called UTC.

2 - Suppression of the leap seconds adjustments which maintains UTC close to
UT1, a time scale based on the Earth's rotation (currently UT1-UTC < .9 s)

3 - The difference of UT1 from UTC should not exceed 1 hour.

4 - The change should take effect at 21 December 2007, 00:00 UTC

If your activity is affected by the content of the US proposal which will be
discussed in November 2005 at the WP-7A, you are urged to react. This could be
the last opportunity before a recommendation is issued by the WP-7A.

If you wish you can express your opinion to your representative(s) at the
WP-7A of ITU (for the list see the ITU website,
index.html) with a copy to Daniel Gambis (, IERS EOP

Daniel Gambis
Earth Orientation Center of the IERS
Observatoire de Paris

Links to various documents related to the above letter

Steve Allen <>
$Id: gambis.html,v 1.9 2015/04/26 01:23:22 sla Exp $