I learned about ntp and its cohort,
ntpdate, when I ran into a machine so slow and old that it couldn’t keep time properly between reboots.
Its internal battery was shot, and powering it down meant the machine would reset at its next startup. And a reset clock triggered a BIOS warning, and … and … and …
The solution was to immediately synchronize its time across the Internet, as soon as it powered up. To that end,
ntpdate became quite useful.
ntpdate -u pool.ntp.org
brings everything back into line. And it’s not just old machines that need nudging now and again. As you can see in the screenshot, even a high(er)-end machine can need adjustment over time.
I don’t bother with regular synchronizing though, just because I don’t think a shift of a few dozen seconds over the course of a couple months is worth the effort.
I must admit I haven’t worked much with ntp beyond
ntpdate; it’s one of those tools I know about but don’t seem to have much call to use.
I know can do quite a bit more, but until the need arises, I am content to leave it as a mystery. 😉