On Thu 2003-06-05T13:10:10 -0700, Brian Garrett hath writ: > time on birth and death certificates is important, but I was not aware of > how important until I saw a posting from Prof. David Mills on > comp.protocols.time.ntp in which he said that UT1 (not UTC) is the legal > standard for death certificates.
The US Code currently specifies mean solar time on 15 degree meridians west of Greenwich. At the time that the US Code was last revised, broadcast time signals in most of the world provided UT2, not UT1. So I would offer that at a sub-second resolution UT2 might be the legal time in the US because it is more "mean" than UT1. Note that the old expression for UT2 is still prominently displayed on the main page of the Earth Orientation Department of the US Naval Observatory http://maia.usno.navy.mil/ I don't really understand why it is there, except as a historical footnote. If it were to be used today, the old expression would best be replaced by a newer one based on the mean orbital motion used in the most recent IAU nutation model and on seasonal earth rotation variations as measured by VLBI over the past 20 years. On the other hand, at the level you can time a death, birth, traffic accident, crime, financial transaction, or whatever, one second is about as good as could be civilly relevant. At that level, UT0, UT1, UT2, GMT, and UTC are currently indistinguishable. There are probably very few tests of legal issues at a finer resolution. And that is why UTC, despite the unilateral power grab at its origin, has been such a useful timescale for the past 30 years. It has SI seconds, and does not deviate in value by more than a second from the historical civil and legal understanding of "time-of-day". I've grown accustomed to tuning into WWV and hearing them announce that they provide time of day, standard time interval, and other related information It would be disappointing to hear it change to atomic time, standard time interval, and other related information -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 [EMAIL PROTECTED] Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E 49 89 0E FE 26 B4 14 93