Get all time zones and their offsets in Linux.

get_tz.sh

#!/bin/bash

for tz in $(timedatectl list-timezones | grep -v 'UTC')
do
    gmtoff=$(zdump -v "$tz" | grep 'gmtoff' | tail -n1 | grep -oE "[^ ]+$")
    tz_offset="${gmtoff:7}"
    
    if [[ "${gmtoff:0:7}" == "gmtoff=" ]]; then
        echo "$tz;$tz_offset"
    fi    
done