Comment 44 for bug 278419

It also worked fine here (using America/Argentina/Buenos_Aires with tzdata 2008h-0ubuntu0.8.04 from hardy-proposed)...

Now if you're living in Salta, Catamarca, La Rioja, San Juan, Mendoza, La Pampa, Neuquén, Rio Negro, Chubut, Santa Cruz or Tierra del Fuego, your time probably changed and it shouldn't...

You have two choices:
select "America/Argentina/San_Luis" or "Etc/GMT-3"... the time will be right, but times in the past can be wrong.

If this is a problem for you, use the instructions I wrote at http://wiki.clueless.com.ar/ActualizarTimezonesConTzdata#parche_baby_2008_10 and select your timezone according to the table beneath it at http://wiki.clueless.com.ar/ActualizarTimezonesConTzdata#provincia_tz_baby