Thanks to Peter Stern and Richard Loken.
/etc/zoneinfo/sources have some files, southamerica is among them. There
I found how to write my own daylight savings file (summer-2006-7.zic):
Rule Brazil 2006 only - Nov 05 00:00 1 S
Rule Brazil 2007 only - Feb 25 00:00 0 -
Zone America/Sao_Paulo -3:00 Brazil BR%sT
# zic summer-2006-7.zic
--
Alexandre Vasconcelos
AIT - SSP/GO
Received on Thu Oct 26 2006 - 18:54:10 NZDT