Comment 2 for bug 267891

As far as I understand it, the ntpdate, which sets the system time, is run from the /etc/network/if-up.d/ntpdate script.

The problem is for periodical updates of the system time, the ntpd daemon has to be installed, which uses a config file, which points to the ntp servers to use.

The standard dhclient program does create such a configfile accordingly and restarts the ntp daemon with that, it the ntp-servers option is set.

network manager fails to do that, so only the ntpdate script is run, which at least adjusts the current system time.