Though timesyncd is fine for most purposes, some applications that are very sensitive to even the slightest perturbations in time may be better served by ntpd, as it uses more sophisticated techniques to constantly and gradually keep the system time on track.
sudo timedatectl set-ntp no
timedatectl
sudo apt-get install ntp
sudo ntpq -p
References
https://www.digitalocean.com/community/tutorials/how-to-set-up-time-synchronization-on-ubuntu-16-04