The following was published as a letter to the editor in the 2005-06 issue of the The AAS Newsletter


A letter from McCarthy, et. al. in the March 2005 Newsletter supports the redefinition of Coordinated Universal Time to be neither coordinated nor universal. For several years, the notion of discontinuing the issuance of leap seconds has been furtively batted about in the precision timing community. No coherent proposal has ever been circulated for comment to the many other communities who would be affected. A workshop in Torino, Italy in May 2003 is the only public meeting that has taken place. The consensus at that workshop was that leap seconds should continue to be issued. Further, the consensus was reached that if a civil time scale is ever constructed without leap seconds (thus disconnecting all clocks from the spinning Earth), that such a new civil time scale should NOT be called UTC, but rather "TI" for International Time.

We support the goal of improving the facilities for providing accurate time signals around the world. This is not the way to reach that goal. The definition of UTC - like all types of Universal Time such as UT1 and UT2 - as a general purpose approximation to the familiar concept of Greenwich Mean Time is critical to astronomical projects, software, and image and catalog data. The history of the redefinition of the term GMT in 1925 attests that a redefined UTC would likewise result in ambiguity and confusion, with the inevitable need for astronomers and society at large to bear the costs of analyzing and replacing all references to UTC in operational and legal systems. This is a mistake we need not repeat.

What should we do instead? Literally - take our time. The current UTC standard is designed to have a life span of hundreds of years. Most systems are not adversely affected by leap seconds since resetting a clock is a common function. Systems that need atomic time are new and specialized and their designers should respond to their own requirements, not transfer them to others. In any event, atomic time is already widely available, for example via GPS. Contrary to the letter in the March Newsletter, the historical and legal reality is that time has always meant Earth rotation because civil time has always been a subdivision of the calendar.

Rob Seaman
Steve Allen

Steve Allen <>
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