ntpdate may be replaced by ntpd -q (one shot).
But I find ntpdate only useful on bootup -- then
run ntpd -- it may upset programs to have
their clocks going backwards. Read the man page...
(from ntpdate man page)
ntpdate can be run manually as necessary to set the host clock, or it can be run from the host startup script to set the clock at boot time. This is useful in
some cases to set the clock initially before starting the NTP daemon ntpd. It is also possible to run ntpdate from a cron script. However, it is important to
note that ntpdate with contrived cron scripts is no substitute for the NTP daemon, which uses sophisticated algorithms to maximize accuracy and reliability
while minimizing resource use. Finally, since ntpdate does not discipline the host clock frequency as does ntpd, the accuracy using ntpdate is limited.