[LEAPSECS] Java: ThreeTen/JSR-310

[Steve Allen]

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                 <sla at ucolick.org>                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