How to enable or disable NTP time synchronization on the Raspberry Pi

Disable NTP:

sudo systemctl disable --now systemd-timesyncd

Enable NTP:

sudo systemctl enable --now systemd-timesyncd

Verifying if NTP is active

You can verify if NTP is active or not by running

timedatectl

Then look for these lines:

System clock synchronized: yes
NTP service: active

System clock synchronized will tell you if the NTP service has successfully synchronized the system time to a NTP time server: yes if synchronized, no if not synchronized.

NTP service will tell you if the NTP service is running, i.e. if it is trying to synchronize the system time to a NTP time server: active if running, inactive when not running

Output with NTP active:

               Local time: Tue 2023-03-14 16:49:28 CET
           Universal time: Tue 2023-03-14 15:49:28 UTC
                 RTC time: Tue 2023-03-14 15:49:28
                Time zone: Europe/Berlin (CET, +0100)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no

Output with NTP inactive:

               Local time: Tue 2023-03-14 16:48:01 CET
           Universal time: Tue 2023-03-14 15:48:01 UTC
                 RTC time: Tue 2023-03-14 15:48:01
                Time zone: Europe/Berlin (CET, +0100)
System clock synchronized: no
              NTP service: inactive
          RTC in local TZ: no