linux clock

there are 2 timepieces in a linux box: hardware and system (i.e. software).

to see hardware clock:

$ hwclock

to see system clock:

$ date

generally, the two clocks are not holding the same time value. to synchronize them, normally adjust the system clock firstly and then set the hardware clock according to the system clock time:

$ date +%T -s '18:12:56'
$ hwclock --systohc