GNU/Linux Desktop Survival Guide
by Graham Williams
Clock: An Explanation
There are two clocks in your computer: a system clock and a hardware clock. The system clock is maintained by the running operating system (e.g., GNU/Linux). It is also said to be maintained by the kernel. The date command talks to the system clock. The hardware clock is part of the actual hardware of the computer and is usually battery backed up. The hwclock command talks to the hardware clock.