[jepler]

The UNIX 'zoneinfo' format is flexible enough to incorporate second offsets, so this can be done on many systems today (Linux, *BSD (the latter including, I assume, OS X)).

The system clock would be kept in TAI (or maybe GPS, which is a fixed number of seconds different than TAI?) and the local time is calculated by applying a timezone offset in seconds.

http://www.ucolick.org/~sla/leapsecs/right+gps.html

[urbit]

Given that the leap-second problem exists, this is the right technical way to deal with it. Unfortunately I've never seen anyone doing this, but they should.

(Of course it'd be ideal if humans were willing to abandon their silly timezones, and just plan schedules in absolute time that made sense for their geography. Alas, not sure we're ready as a species for this level of change.)