Commission 31    TIME

• Report 2005-2008 pdf file
• Circular letters of Commission 31
• 1999-2002 (IAU Transactions XXVA, 2002) pdf file
• Report of business session at the 24th General Assembly (IAU Transactions XXIVB, 2000) pdf file
• Report 1996-1999 (IAU Transactions XXIVA, 1999) pdf file
• Report 2002-2005 pdf file
• Report of scientific session, 26th general assembly (Pragues 2006) pdf file

Commission 31 members participate in Division 1 Working Groups: the WG on Astronomical Standards WGAS and in particular its sub-group , the WG Relativity in Celestial Mechanics and Astrometry RCMA ,which has been renamed RCMAM in January 2001 to explicitly include metrology, which was upgraded to the new IAU Commission 52 "Relativity in Fundamental Astronomy" iat the 28th GA, Prague, 2006.

The WG Nomenclature for Fundamental Astronomy (2003-2006),and presently Numerical Standards in Fundamental Astronomy, formed at the 26th GA, 2006 Commission 31 members also participated to the BIPM/IAU Joint Committee on Relativity JCR (closed in January 2001).

Since 1999, a number of organizations initiated a review on the future of the UTC system (insertion of leap seconds between TAI and UTC to keep UT1-UTC <0.9 s.

Main options were

1. maintain the status quo,
2. modify the leap second procedure (e.g. suppress them),
3. use another time scale (e.g. TAI).

The Consultative Committee for Time and Frequency (CCTF) in 1999 discussed the matter and the director of the BIPM sent letters to several international unions and navigation agencies. The International Union of Radio Science (URSI) created a WG, chaired by D.N. Matsakis (Commission 31 President). In 2000 the International Telecommunications Union (ITU) created a Special Rapporteur Group (SRG) in the Working Party 7A, to study the new Question ITU-R 236/7 on "The future of the UTC time scale".
The IAU 24th GA in 2000 passed Resolution B2 to recommend the creation of a WG in collaboration with the URSI, ITU, BIPM, IERS and navigation agencies. The ITU Special Rapporteur Group, organized a meeting in Torrino, Italy in May of 2003 and in essence resricted the options under consideration to either no change or else eliminating new leap seconds after a date near 2022. Commission 31 members are active in these groups. See the discussion forum, and a Web page maintained by Markus Kuhn specializing in links on leap second matters.
The working group on the Definition of Coordinated Universal Time was dissolved at the 26th GA in 2006.