Red Hat Knowledgebase

Sometimes, it is needed to prevent daylight saving time adjustment set the timezone to GMT and instead specify the desired hour offset. Accordingly to the Posix standard the offset in the time zone is defined as "the time value you must add to the local time to get a Coordinated Universal Time value" (from: http://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html). This means that if the desired time is one hour plus GMT the timezone to specify will be GMT-1 and not GMT+1.

For example if it is required to prevent the daylight saving time adjustment on a machine that is located in Italy where the time is one hour plus GMT you can follow these steps:

Open /etc/sysconfig/clock and set the timezone to Etc/GMT-1:

ZONE="Etc/GMT-1"

Replace the current /etc/localtime with the GMT-1 zone info file:

# ln -sf /usr/share/zoneinfo/Etc/GMT-1 /etc/localtime

Check that the timemezone change is in effective using date command:

# date
Tue Sep 11 11:17:45 BST 2007