This one is fairly simple. All of thee zone info files are located in /usr/share/zoneinfo/, divided by region. I’m in Croatia so setting up time to be the same as in Zagreb is done by sym-linking appropriate zone file to /etc/localtime:

ln -sf /usr/share/zoneinfo/Europe/Zagreb /etc/localtime

As I use jails on FreeBSD, to avoid setting this up on every single jail, I have flavor within ezjail defined which has default settings that I usually have on all jails. Time zone is one of those things and can be defined with:

cd /usr/jails/flavours/YOURFLAVOUR/etc
ln -s /usr/share/zoneinfo/Europe/Zagreb localtime