NPT or Network Time Protocol is a protocol for clock synchronization.
To use ntp in Linux arch you have to install the required package called
# pacman -S ntp
Enable it at boot so every time you boot the system the clock will be synchronized.
# systemctl enable ntpd.service
Update the time.
# ntpd -qg
Once you have systemd managing this operation, you should never have to worry about setting the clock again.