I have installed Arch Linux on my Raspberry Pi from rasparch-exton-1680mb-180402.zip, successfully updated and have set my Locale to en_AU.UTF-8 and this looks OK.
timedatectl continues to show Time zone: UTC
timedatectl set-timezone AEDT
returns Invalid time zone
ln -sf /usr/share/zoneinfo/Australia/Sydney /etc/localtime