We used the ntp service on the mangoES devices for time syncing. We just had to update /etc/ntp.conf with our internal ntp server ip addresses.
It looks like the ntp service/daemon isn't available on the GT mangoes. I have tried running 'sudo apt install ntp', but It's getting blocked by the firewall. Do you have a recommended way to set up time syncing on the mangoGT?
setup of ntp time sync on GT mangoes
I have discovered that the system-timesyncd service is installed and runs out of the box (on the mangoGT). It's not able to sync for us with the default debian servers due to firewall restrictions. I just needed to put our local ntp servers in /etc/system/timesyncd.conf and it works fine.