Dennis D. McCarthy worked in the Time Service and Earth Orientation Departments of the U. S. Naval Observatory (USNO) for the past 40 years, reaching the position of Director of Time at USNO. He has been involved in both the improvements in time keeping and time transfer, and the advances in the observational determination, analyses and prediction of accurate Earth orientation. Dr. McCarthy is the author of a large number of papers on time scales and Earth orientation.#60;br#62; #60;br#62;P. Kenneth Seidelmann worked in the Nautical Almanac and Orbital Mechanics Departments of the U. S. Naval Observatory for 35 years, reaching the level of Director of Astrometry at USNO. He has been… involved in the development of astronomical ephemerides, relativistic dynamical time scales, space missions, and the applications of improved astrometric accuracy. He is currently a Research Professor at the University of Virginia. Professor Seidelmann is editor of the #8242;Explanatory Supplement to the Astronomical Almanac#8242;, coauthor of #8242;Fundamentals of Astrometry#8242;, and author of a large number of papers on fundamental astronomy.#60;br#62;