[LEAPSECS] Negative TAI-UTC

[Zefram]

Clive D.W. Feather wrote:
>probability is that TAI-UTC will ever be negative? Should data structures
>be designed to handle this case or not bother?

Data structures should certainly allow for the possibility, but in
space-constrained cases can be optimised based on the understanding that
it's relatively unlikely.  If a fixed-size field is being designed,
then the range of TAI-UTC values that it can accommodate can be made
asymmetric, favouring positive values.  An 8-bit field might reasonably be
made to use excess-32 encoding, encompassing values [-32, 223], giving it
a good chance of covering the next century's evolution of Earth rotation.
(8 bits is minimal for that design objective; I'd press for more bits
if possible.)  A variable-length encoding can in principle cover all
possible values, but could still benefit by making the representations
of negative numbers longer than the representations of positive numbers.

-zefram