System Clock vs Hardware Clock on Linux - Linux Tutorials - Learn Linux Configuration

The system clock and the hardware clock are used for different purposes on a Linux system. The system clock is maintained by the operating system, and the hardware clock is maintained in BIOS. The hardware clock will continue to keep time when the computer is powered off, thanks to the CMOS battery on the motherboard. The system clock maintains time by querying online time servers whenever the computer is powered on.

This is a companion discussion topic for the original entry at

“System Any Linux distro”
False. Only applies to Linux distros with systemd installed. Yes, it’s the predominant init system at the moment but it’s not even close to as universal as SysV was.