by applying this patch we:

• change current NTP services offered by the FreeBSD Installer;
• no longer offer ntpdate to be enabled and started on boot;
• start offering the option to make ntpd set the date and time on boot itself.

the motivation for this change comes from the ntpdate(8) manpage:

Note: The functionality of this program is now available in the ntpd(8)
program. See the -q command line option in the ntpd(8) page. After a
suitable period of mourning, the ntpdate utility is to be retired from
this distribution.

offering ntpd_sync_on_start to be used will give folks the option to append -g into ntpd's command_args.

according to ntpd(8)'s manpage:

-g, --panicgate
             Allow the first adjustment to be Big.  This option may appear an
             unlimited number of times.

             Normally, ntpd exits with a message to the system log if the
             offset exceeds the panic threshold, which is 1000 s by default.
             This option allows the time to be set to any value without
             restriction; however, this can happen only once. If the threshold
             is exceeded after that, ntpd will exit with a message to the
             system log. This option can be used with the -q and -x options.
             See the tinker configuration file directive for other options.