Timezone is set in the file /etc/TZ (uclibc standard), which is a symlink to /mnt/ramdisk/TZ. The contents of this file specify the timezone. You can learn more about the exact format in the bering-uclibc docs. To make it short, for most of the Europe, the correct timezone is about CET-1CEST-2,M3.5.0/02:00,M10.5.0/03:00. So changing it will be something like:
echo CET-1CEST-2,M3.5.0/02:00,M10.5.0/03:00 > /etc/TZ
Unlike most services, you don’t have to restart anything to actually change the timezone, the effect is basically immediate, also for running services.