Intro

The files with information about time zones and the popular “daylight saving” are in /usr/share/zoneinfo. They can be inspected with:

zdump -v "archivo"

In our case it’s very common for the dates when the clock change happens to be modified; to fix this, these files have to be recompiled after modifying them, which is done with the zic command.

The zone definitions are downloaded from ftp://elsie.nci.nih.gov/pub/

Procedure (example for Paraguay)

# Realizar copia de seguridad  
cp -rp /usr/share/zoneinfo{,.$(date +%Y%m%d)}

# Obtener source:  
mkdir -p /tmp/tzdata && cd /tmp/tzdata  
wget 'ftp://elsie.nci.nih.gov/pub/tzdata*.tar.gz'

# Realizar modificacion
tar xvzf tzdata*
vi southamerica

# Compilar  
/usr/sbin/zic southamerica

# Definir zona horaria  
cp /usr/share/zoneinfo/America/Asuncion /etc/localtime