NTP is robust, but rather complicated, and I can never remember the correct options for the things I need to do. These are my notes for some common NTP tasks.
Compare localhost time to known server: ntpdate -q pool.ntp.org
NEW: Immediately switch localhost time to correct time from known server: ntpd -gq
(NOTE: you have to stop the regular NTP service for this to work)
OLD: Immediately switch localhost time to correct time from known server: ntpdate -b pool.ntp.org
(NOTE: you have to stop the regular NTP service for this to work)
Show the hardware clock: hwclock --show
(NOTE: sudo required)
Sync the NTP time to the hardware clock: hwclock --systohc
(NOTE: sudo required)