hwclock --systohc; hwclock; date
query and set the hardware clock (RTC)
hwclock --systohc; hwclock; date
hwclock -r or hwclock --show # read hwclock -w or hwclock --systohc # write hwclock -s or hwclock --hctosys # set sys hwclock -a or hwclock --adjust hwclock -v or hwclock --version hwclock --set --date=newdate hwclock --getepoch hwclock --setepoch --epoch=year