NTP: Network Time Protocol
NTP Server allows to synchronize the time of the device with the time provided by the network.
On recent installation of dietpi OS (bulleye) I have encountered situation where the service systemd-timesyncd.service does not run, cannot be started, without any good explanation.
By browsing the net, I found a recommendation consisting in installing htpdate
apt update
apt install htpdate
then
sudo reboot
Not entirely sure why, but on two devices (PiWordPress and PiDatabase) the issue has disappeared.
I have also written a script to monitor the status of the service and restart it automatically in case it is discovered as inactive. This service runs at regular interval thanks to Cron task