On Fri 2011-01-28T18:03:07 +0000, Stephen Colebourne hath writ: > JSR-310 addresses the definition of 1970-01-01Z (by defining the > TAI-UTC gap as fixed at 10 seconds prior to 1972.
This is pointless silliness. This is defining a time scale which did not exist and presuming that it can be used for something practical. It cannot. For any precision purposes TAI and UTC did not exist before 1972-01-01. TAI only got its name in 1971, and the only way to access it prior to 1972-01-01 was by painstaking tabular lookup of the offsets of the time signal used for a time stamp. Until that instant the UTC being broadcast by the Soviet Union (and other stations) differed from other broadcasts by milliseconds. I can go over to the library and find the BIH Circular with the exact number, but it was not small. Before 1972 the only practically available time scales were nebulously synchronized versions of UT. Those are measures of earth rotation, suitable for subdividing the days of the calendar. Presuming that they are suitable for any other purpose, or defining a general-purpose scheme to make use of them for precision purposes, is a mistake. All proleptic time scales are dangerous, for in the absence of a contemporary authority to define what they were, any one interpretation is likely to differ from another. -- Steve Allen <[email protected]> WGS-84 (GPS) UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99855 University of California Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
