Saving date and time to hardware clock manually

If you change date and time in console, the hardware clock may not be updated instantly. There's a script usually find in many distros that save the date and time to hardware clock before the computer off or restart. Some GUI apps changed the hardware clock if you change the software clock. If you want to change the hardware clock manually, here's the command:

hwclock --systohc

and obviously, you have to run it as root.